If at some point in the past 24 hours you've asked, "isn't weather as warm as THIS unusual? Temperatures aren't typically anywhere near 80-degrees on April 1, are they?", then pat yourself on the back! Your "read" on the unusual nature of this warm spell is right on and very perceptive. Thursday's predicted 82-degrees high is nearly 30-degrees above "normal" early April levels and would tie the 64 year old record for this date set in 1946. Such a high would be 29-degrees above the 53 recorded a year ago.
An analysis of Chicago's observational weather record, which dates back to 1871, reveals only 11 of the past 140 years--8 percent of them---have managed to produce an 80-degree temperature by the close of April 1. A reading at or above 80 degrees Thursday would become only the 12th time since records began that the city's official temperature has reached or exceeded 80 at such an early date!
It wasn't until April 24th a year ago---more than three weeks from today---that the mercury first made it to 84-degrees in 2009. The year's first 80-degree reading typically occurs on or about April 22 at Midway Airport, and April 25 at O'Hare.
Wednesday's 77-degree high beckons Chicagoans outdoors in droves
Temperatures Wednesday broke above 70 just after the noon hour---the first 70-degree reading here since early November and 2010's warmest. Other area highs Wednesday included 81-degrees at Itasca and 80-degrees at Weather Bug sensors at Buffalo Grove and Aurora. High temperatures at Waukegan and Gary---both on the shores of chilly Lake Michigan---made it 79-degrees.
Wind trajectory forecasts produced by one of Environment Canada's computer forecast models, which offer an indication of the source of Thursday's warmth in Chicago, predicts the air over the city by mid and late afternoon was over Texas Wednesday.
Brush fires erupt in the wake of the sunniest March in 9 years; driest in 5 years
The remarkable warmth comes on the heels of Chicago's sunniest March in 9 years and its driest in 5 years. The month's 1.55 inches at O'Hare was a fraction of the 5.20 inches recorded last March. It's little wonder a series of small brush fires have erupted in recent days. A combination of strong winds, low humidities and warm temperatures Wednesday proved the perfect combination for the eruption of fires at Lake in the Hills, Vernon Hills and Willowbrook. Some roads in the Willowbrook area had to be closed for a time Wednesday evening.
The Chicago area's precipitation trend is sure to be monitored closely in coming months as spring planting nears. Several 2-week computer rainfall projections generated Wednesday hint elevated rainfall is possible over the period. The first rains and even some thunderstorms are possible Saturday and several additional waves of rain could occur next week.
Boston records wettest March; some suburban totals top 20 inches
Rivers continue to rise in the Northeast where historic flooding is on the way. Boston recorded 14.87 inches over the past month making it the wettest March on record and the 2nd wettest single month ever. A typical March produces 3.85 inches there. Rainfall tallies in some surrounding communities topped 20 inches.
Dear Tom,
What's the difference between scattered and isolated thunderstorms?
-Joann Spencer
Dear Joann,
When applied to thunderstorms, "scattered" and "isolated" refer to the amount of the forecast area experiencing random, disorganized thunderstorms.
Scattered thunderstorms have an areal coverage at any moment of 10 to 50 percent and whose occurrence is random -- that is, displaying no organization such as lines or clusters. Isolated thunderstorms are "loners," well removed from any other thunderstorms and affecting less than 10 percent of the area.
"Scattered" and "isolated" refer only to areal coverage and do not address other thunderstorm issues such as severity, lightning intensity or flooding. The parent thunderstorm of the devastating Plainfield tornado of Aug. 28, 1990, that claimed 27 lives was an isolated storm.
The area's warmest weather in over half a year arrives Wednesday---the beginning of a multi-day warm spell expected to send temperatures surging to within striking distance---but probably a degree or two short of---record highs in the low 80s Thursday and Friday. The warmth's arrival coincides with March's close. The 75-degree high predicted here Wednesday would become 2010's first 70+ reading while 81 degree highs forecast both Thursday---April Fool's Day, but NO joke---and Friday are at levels 30-degrees above normal. Those high temps are more typical of June than early April and eclipse 53-degree highs on the same dates a year earlier.
The incoming warm spell continues an above normal temperature trend which has dominated March and pushed readings 1.5-degrees above a comparable period a year ago. The month's 2010 average of 40.9-degrees is 4.5-degrees above the long term average of 36.4-degrees, making it the 25th mildest Chicago March of the past 139 years.
An air mass responsible for 80s from western Iowa into the Plains Tuesday, is behind the warmth. Gusty southerly winds stacked vertically tens of thousand of feet into the atmosphere are helping propel the temperature surge.
March rainfall lagging the same period a year ago as area farmers plan for planting
With a new planting season just around the corner for area farmers and gardeners, soils remain a bit wet in the area---but possess a fraction of the moisture which saturated them a year ago. March has generated only a third of the rain observed a year ago to date---1.55 inches versus last March's full month tally of 5.20 inches. Last year's regular March downpours led into an incredibly challenging growing season which was so wet, many Illinois farmers were months late in getting crops into the ground.
Soil moisture is monitored carefully by long-range weather forecasters because of its potential to impact warm season temperatures. In-house analyses of Chicago's summer temperatures in the seasons which have followed 21 drier than normal Marches since 1871, indicate a slight majority (62 percent of them) went to produce above average June through August temperatures.
Last summer's abnormally cool temperatures and, in the eyes of the area's hot-weather enthusiasts, its dismal four-days of 90-degree temperatures---17 such days are considered typical---was likely a by-product of prolific precipitation which began in February and continued through June. The precipitation soaked area soils, a development which makes it hard for really hot weather to gain a foothold. As temperatures warm over wet soil, evaporation rates increase and the moisture which returns to the atmosphere is available to produce more than the typical levels of cloud-cover and precipitation. Both impede warming and often lead to cooler than normal summer temperatures.
Though soil moisture isn't as extreme in the Chicago area as a year ago, a large area of the Midwest to Chicago's west remains wetter than normal. It will be interesting to see if this ends up affecting the region's warm season temperatures.
Dear Tom,
I remember getting caught in an early April snowstorm in the middle 1970s and had to abandon my car. Can you provide any details?
--Malcolm Vye
Dear Malcolm,
You fell victim to one of Chicago's biggest late-season snowstorms, the April 2-3, 1975, storm that officially brought 9.8 inches of heavy, wet snow to Chicago, but some suburban areas received more than a foot. The snow was especially shocking because of the mild weather that preceded it in mid-March with eight straight days above 50 degrees including a 74 degree high March. 21. After a brief cool snap the mercury rebounded to a balmy 62 on March 31. As April opened temperatures plummeted and the snow arrived accompanied by thunder and lightning and high winds that piled the snow into large drifts. The storm turned out to be the biggest snow of the 1974-75 snow season that recorded 52.2 inches.
As the trajectory of winds over Chicago shift from easterly to more
southerly, the impact of the cool 40-degree Lake Michigan waters will
greatly diminish today. A predominantly south wind Tuesday will allow
temperatures to warm well into the 60s in western and southern
sections.
Near record high Thursday
Wednesday
could see Chicago's first 70-degree high of 2010, Then aided by a third
consecutive day with southerly winds, readings could warm above 80
degrees Thursday, threatening the record high of 82 degrees set on that
date 64 years ago. The last time Chicago recorded an official high
temperatures in the 80s was last September 15th when the mercury hit 82
degrees. Eighty-degree readings are extremely rare this time of the
year--a search of Chicago weather records dating back to 1871 came up
with only 7 days out of the possible 417 with a high of 80-degrees plus
for the March 31-April 2 period. Back-to-back 80s are possible, if
clouds do not interfere Friday. It looks to be a good bet that we will
reach 70-degrees Wednesday, Thursday and Friday, if so, it will be the
first time ever consecutive 70-degree plus readings occurred on those
dates.
Dear Tom,
I recall years ago watching a program about weather events that changed American history. Mentioned in the program was a tornado that could have changed the course of music, but I have forgotten what that was about. Can you provide any details?
Robert Utzinger
Dear Robert,
Indeed we can. At 8:55 p.m. on April 5, 1936, a devastating F5 tornado tore through Tupelo, Miss. With 216 deaths and 2,000 injuries, it stands as the fourth-worst tornado in the U.S. The tornado missed Tupelo's downtown area but ravaged residential sections, and it is likely the number of deaths and injuries was significantly higher because of incomplete and hasty tabulations in the wake of the storm. However, one of the survivors of that storm was an infant named Elvis Aaron Presley.
Chicagoans for the most part have shivered through a chilly spring with only a handful of mild days in the 60s, but a dramatic warm-up is on the way and should boost the mercury to unseasonably warm levels later this week, possibly threatening some record highs. After a seasonably cool start to the week Monday, readings will jump to 60 Tuesday then rocket into the 70s on Wednesday for the first time this year. But April 1 promises to take the warm-weather honors as the mercury could reach 80 degrees as gusty southwest winds deliver the warm air all the way to the lakefront. If the 80-degree high verifies it would be the city's first since last Sept. 15 and threaten the 82-degree April 1 record maximum established in 1946. Typically the city's first 80 does not occur until about April 22.
Twisters rip North Carolina
Several tornadoes hit portions of central North Carolina Sunday evening, causing several injuries and damage to more than 20 homes in the High Point area. Other twisters were reported near Thomasville, Lexington and Gaston with damage to mobile homes. Earlier in the afternoon another tornado was reported in east-central Florida near Melbourne.
Dear Tom,
My parents told me about a major tornado outbreak that took place on Palm Sunday in the 1960s. When and where did it occur?
Heidi Larkin
Dear Heidi,
Severe weather is no stranger to Palm Sunday with its March or April occurrence during the spring storm season. Your parents were referring to the outbreak of tornadoes that took place on April 11, 1965. Nearly 50 confirmed twisters struck areas from eastern Iowa to central Ohio killing 271 people, injuring almost 3,500 and causing more than $250 million of property damage. Six fatalities and 74 injuries were recorded in the Chicago area when an F4 twister tore up an 11-mile-long stretch from Crystal Lake to Wauconda. Five of the fatalities were in southeast Crystal Lake where 45 homes were demolished. The sixth death was at Island Lake where the twister destroyed or damaged four blocks of homes.
With the exception of a few days with temperatures in the lower and
middle 60s, The spring 2010 has been a chilly one in the Chicago area.
The season's highest reading thus far has been only 65 degrees, on
March 19. However, big changes lie just ahead. By mid week, a powerful
surge of southerly winds sends temperatures soaring to the highest
levels in four and one-half months, reaching into the lower 70s by
Wednesday and, with luck, approaching 80 degrees on Friday. Chicagoans
last experienced 70-degree warmth on Nov. 7, when the mercury peaked at
71. Before the warm-up, though, we'll have to endure two more chilly
days. Sunday will feel especially cold, with stiff northeast winds
adding to the discomfort of morning rain and temperatures struggling to
get into the 40s. Winds subside, sunshine returns and temperatures
moderate a little on Monday.
Dear Tom,
With our first 70-degree day in sight, have we ever gone through March and April without getting one?
William J. Ooms Jr.
Dear William,
It has happened only once, and that was in 1874 when the city did not see its first 70-degree day until May 7. In those days the official temperature site was downtown near Lake Michigan where the typical arrival date for the season's first 70 is April 9. Inland areas usually record their first 70 about March 25. Despite the late arrival of spring warmth, the summer of 1874 did go on to produce some hot weather. There were 17 days in the 90s, the two hottest being a 99-degree high July 6 and a 98 on July 25. There were no extended heat waves that summer, but the city did record three straight 90s, Aug. 19 to 21.
Illinois' first thunderstorms of spring usually arrive in March, but it has been relatively tranquil in the Chicago area in recent weeks. This has masked a climatological fact: March is the beginning of the Illinois tornado season. In fact, the worst tornado disaster in the United States -- the Tri-State Tornado of March 18, 1925, was primarily an Illinois event. Of the 695 deaths in Missouri, Illinois and Indiana from the tornado, 606 of them were in Illinois.
Changes ahead
A major weather pattern change is under way, the result of which will be sharply colder temperatures across the western United States next week and much warmer readings in the Great Plains and Midwest. Temperature contrasts such as those fuel strong thunderstorms and will increase the risk of severe weather in the Plains by midweek.
-- By Richard Koeneman, WGN Weather Center Meteorologist
Dear Tom,
Does the relative humidity ever go below 10 percent anywhere?
--Sara McPhail
Dear Sara,
Occurrences of very low relative humidity are rare and are confined almost exclusively to deserts. Chicago's relative humidity has never dropped below 10 percent, and its all-time low humidity value is 13 percent, measured on three occasions: May 10, 1934; April 11, 1956; and April 8, 1971. The world's lowest relative humidity value seems to be 2 percent and has been recorded at several U.S. locations -- all desert locations -- such as Las Vegas; Phoenix and Yuma, Ariz.; and Death Valley, Calif. Worldwide, readings of 2 percent have been recorded in the Sahara and have assuredly occurred in other desert regions around the world, though data are sparse from those areas.
Spring, far more than any other season, is noted for its variable and turbulent weather characterized more often than not by huge temperature swings. Chicago is about to experience a dramatic example of that as a major weather pattern change occurs during the next seven days. During that period. the city's temperatures are forecast to surge more than 50 degrees from Friday morning's low in the lower 20s to afternoon readings in the middle 70s by Thursday. Chicago last experienced 70-degree warmth on Nov. 8 (71 degrees).
About winter
Chicago's lowest temperature this past winter was 1 degree below zero (Jan. 3) and that was the city's only subzero day. On average, the city experiences seven subzero days during its cold season.
Dear Tom,
As you have mentioned, Chicago's snow total this season is near 55 inches, and the north suburbs have had even more. But with April only a few days away, can I assume that's it?
--William Morrison, Waukegan
Dear William,
Chicago's snow season is winding down, but it's premature to dismiss the possibility of additional snow at the end of March. On average, the city's full snow season delivers 36.8 inches with 97 percent of it coming down by April 1. That means 3 percent, or 1.2 inches, is yet to occur.
The weather isn't bound by those climatological averages, of course, and only 66 Aprils out of 125, or 53 percent, have produced measurable snow (at least 0.1 inch). Significant snows, arbitrarily defined as 3.0 inches or more, occur in 1 out of 4 Aprils, and 1 out of 20 Aprils have a storm of at least 6.0 inches.
Talk about a temperature roller coaster; that's the head-spinning ups and downs in readings in store for Chicago area residents in upcoming days. From Friday's forecast minimum of 23 degrees to Wednesday's projected high of 70, the area could experience a temperature surge of 47 degrees, but it won't be a steady ride -- there will be ups and downs along the way.
Florida's cold winter
With the official arrival of spring this past weekend, a record cold winter at Key West (the southernmost city in the continental United States) came to a close. The winter (astronomical winter, Dec. 22 to March 20) there had an average temperature of 65.3 degrees, tying the winter of 1977-78 as that city's coldest. Chicago's winter temperature average was 28.6 degrees, nearly 37 degrees colder
Dear Tom,
It seems that the weather on the weekends is inclement more often than during the week, but this defies logic. Can you shed some light on this issue?
Tim Mallis
Dear Tim,
There's a name for a sunny day that follows two cloudy, rainy days: It's called Monday. That joke has been floating through the meteorological community, and elsewhere, for as long as we can remember, and it certainly seems to have validity. We all have memories of weekend plans disrupted by the weather or outdoor weekend events that were washed out -- and that's the key to the source of the "rainy weekend" syndrome. We remember the disruptions and washouts. However, a computer scan of Chicago's precipitation records reveals that precipitation does not have "favorite days." Averaged through the years, precipitation falls on one day out of three, regardless of the day of the week.
Illinois usually experiences turbulent, thundery weather in March, but it's been relatively tranquil in recent weeks -- and rather sunny, as well. As measured at Midway Airport, Chicago logged 53 percent of possible sunshine through the first 23 days of the month. That makes this month the sunniest March in nine years in Chicago. Monday and Tuesday were absolutely sunny, with each day registering 100 percent of possible sunshine, but the city's spell of sunny skies is ending. Two storm systems featuring rain, extensive cloudiness and cooler temperatures are heading toward Chicago. The first arrives Thursday with rain, chilly readings and raw northeast winds that may gust to 40 mph. The second brings rain and another bout of strong northeast winds Sunday. But the chill won't last. Computer models hold out the possibility of 70 degrees by April 1.
Dear Tom,
I heard mention of "supercells" that caused the recent tornadoes in Oklahoma. What are supercells?
--Martin Levy
Dear Martin,
Supercells are a special breed of thunderstorms --- huge, severe and rotating (in the sense that air in the 10- to 50-mile wind field in which supercells are embedded spirals inward, usually counterclockwise). Most uniquely, supercells persist for many hours, whereas thunderstorms usually move though a life cycle of an hour or less.
Thunderstorms consist of rising currents of warm, moist air that deliver the storm's energy and cool downdrafts in the rain area. Normally, downdraft air undercuts the inflow of warm air within an hour and the storm dies. In supercells, the updraft-downdraft combination is in unique balance and the storm persists for many hours, allowing more time for intensification and severe-weather production.
Chicago has escaped the March weather woes that afflicted much of the nation, but changes are afoot. Until now, the city has registered above-normal temperatures -- an average excess of 6 degrees per day from March 1 through Tuesday -- and, with the exception of some slushy snow Saturday, no big storms. With luck, the pattern will persist before sharply colder temperatures arrive this weekend. Two storm system crossing the Midwest in coming days are forecast to remain far enough south to spare the city the bulk of their precipitation.
Chilly stretch in Florida
Chicagoans might find it difficult to sympathize, but temperatures in normally warm Jacksonville, Fla., failed to reach 80 degrees for the 97th consecutive day. That's the city's fourth longest stretch ever.
Dear Tom,
When do fireflies (lightning bugs) start to come out in Chicago? I understand it has to do with warmth.
---Donna Morris
Dear Donna,
"One of the most enchanting sights of the season is the delicate light of fireflies blinking in the night. ... These graceful little stars put on a magical show that would make even Tinkerbell jealous! ... They don't sting, bite, attack or carry disease, they're not poisonous, and they don't even fly very fast. What's not to like about fireflies?" --Signs of Spring Magazine.
Firefly larvae hatch from eggs deposited in damp soil in the summer. They live one or two years underground, develop into pupae in late spring and emerge as adults in early summer. In the Chicago area, fireflies begin to appear in June and remain active through August. Their life cycle changes are apparently genetically controlled, rather than determined by temperatures.
March is proverbially a blustery month in Chicago. Its weather, more often than not, is especially unsettled as warm and cold air masses jostle for supremacy. And following a winter that delivered colder temperatures and considerably more snow than normal, most Chicagoans are anxiously anticipating the arrival of spring.
To date, this March has not been a disappointment: Its weather has been uncharacteristically quiet and storm-free -- Saturday's snow notwithstanding. The month's temperatures have averaged 5.6 degrees above normal and severe thunderstorms, often an increasing threat in northern Illinois in March, have so far not entered the picture.
The quiet pattern, at least by March standards, is set to continue a few more days. Temperatures will take a nice upward bump today and Tuesday and a few showers are possible midweek, then more showers are possible next weekend.
-- By Richard Koeneman, WGN Weather Center Meteorologist
Dear Tom,
Why do we have frost when low temperatures at night are in the 40s? Golfers are made to wait until the frost melts before they can tee off.
-- Tom Mezyk
Dear Tom,
The National Weather Service, following international standards, measures air temperatures at a height of four to five feet above the ground. On clear, calm and dry nights when heat radiates strongly away from the ground (so-called "radiative cooling"), air temperatures right at ground level sometimes drop 5 to 8 degrees lower than readings at thermometer height. In addition, surfaces such as blades of grass chill even more quickly than the ground-level air in which they are immersed. One result of this localized cooling is frosty grass even though "official" air temperatures are 5 to 10 degrees above freezing. Frost that forms on such nights disappears quickly in direct sunlight or when a morning breeze begins to stir.
After a mostly cloudy cool day Sunday, astronomical spring will shift
in gear Monday and with winds shifting to the southwest temperatures
are expected to return to the 60-degree level by Tuesday afternoon.
This means the thin layer of snow deposited over much of the area
Saturday--greatest amounts were between 2 and 3 inches--will probably
be gone, perhaps as soon as Monday.
Heavy snows to the south
As
a strong low pressure system tracks east out of the southern plains,
Winter Storm Warnings were posted for eastern Oklahoma, southeast
Kansas, Southwest Missouri and northwestern Arkansas where
Saturday-Sunday snowstorm totals of 6 to 12 inches were forecast. The
cold air was to moderate, with primarily rain expected as the low
center tracks east reaching the mid-Atlantic coast Tuesday.
Warmup next weekend
Wednesday
through Friday northeastern Illinois temperatures are expected to
average a little above seasonal norms with 60-degree readings marking
the return of strong southerly winds the start of next weekend.
Dear Tom,
On March 11, I saw a large rainbow with another one that was very dim surrounding it. Were my eyes playing tricks on me?
--Terry Sandhill
Dear Terry,
The spectacle of a double rainbow --- so-called primary and secondary (or supernumerary) --- is a grand sight and several were seen across northern Illinois and Indiana on March 11.
Rainbows form when sunlight passes into raindrops and, after reflection within the drops and refraction, leaves the raindrops and returns to our eyes separated into the colors of the spectrum. The color sequence in the primary rainbow, from the outside inward, is red, yellow, green and blue. A secondary, and fainter, rainbow forms above the primary when some of the light is reflected twice within each raindrop. The supernumerary color sequence is reversed because of the double reflection.
The return of wintry weather to the Chicago area was abrupt and unceremonious late Friday. One minute it was like spring, the next minute it was as if the clocks had been turned back to winter. Friday had been the year's warmest to date before the powerful cold front hit. Highs reached 65 degrees at O'Hare, Midway and the lakefront, and soared to 68 at Buffalo Grove and 67 at Itasca. But the unseasonable warmth--with highs 20 degrees above historic mid-March norms here--proved no match for the onslaught of cold air.
While temperatures began dropping across the far northern suburbs as early as mid-afternoon, the city was invaded by 30+ mph gusts late in the evening rush hour, initiating a thermal tailspin. In a single hour's time, readings at the Harrison-Dever Crib, three miles off Chicago's shoreline, dove from 62 to 42-degrees--a 20-degree pullback--between 6 and 7 p.m. The same period saw readings at Northerly Island on the city's lakefront plunge from 64 to 47 degrees. A minute-by-minute temperature analysis off a Weather Bug sensor on the South Side at the Dumas Elementary School indicated readings there plunged 15 degrees in only 12 minutes--from 62 degrees at 6:39 p.m. to 47 at 6:51. By late evening, North Shore readings were uniformly up to 25 degrees off the 60-degree levels of only hours before.
The pullback was hardly limited to Chicago. A huge swath of terrain well over a thousand miles across and extending from New Mexico, Utah and Arizona to the Great Lakes, registered 24-hour temperatures drops of as much as 40 degrees between Thursday and Friday. By late evening, snow was falling and piling up over sections of 14 states--with the heaviest totals still looming in the southern Plains and western Midwest.
By day's end, Ouray, Colo., had a fresh 15.2" cover of snow while Red River, N.M., had been buried beneath a foot of new snow and Vail, Colo., registered 11". Snow intensity farther east was less spectacular with 2.6" down in Fremont, 1.5" in Polk City, Iowa, and a trace in Madison, Wis.
Blizzard in wake of Friday's 72 could push Oklahoma City snow tally to all time record
A storm system, predicted to intensify over the southern Plains Saturday then drift east/northeast, may well spare Chicago's its worst blow. But residents of Oklahoma City, where this season has already generated 20.7" of snow--more than four times normal--may not be as lucky. With only 4.5" separating the current seasonal tally from the city's all-time record total of 25.2" set in 1947-48, predictions of 4 to 10" of snow may push the 2009-10 season to the all-time snowiest before this weekend ends.
Storms such as this weekend's have, on occasion, been known to spin north to Chicago. But, models indicate the system is to close off then drift east/northeastward through Sunday and into Monday only swiping Chicago while producing its most prodigious rains and snows to the south and southwest. Areas of Kansas, Oklahoma, portions of western Missouri and northwest Arkansas are to sit at the epicenter of this storm's heaviest snows.
Patches of cold rain and snow which extend into northern Illinois Saturday are likely to occur for the most part in above-freezing temperatures and over ground warmed by two days of 60s. That plus winds off Lake Michigan waters which are averaging 40 degrees should be enough to--barring an unexpected northward jog in the storm track--impede huge accumulations here.
Dear Tom,
Chicago certainly has a lot of strange weather, but are there any meteorological "impossibilities" such as an 80-degree reading in the winter or snowfall in July?
--Richard Lurie, Chicago
Dear Richard,
It's easy to pose a hypothetical "meteorological impossibility" for Chicago -- a tornado with 1,000-mph winds or a temperature of 200 degrees would do the trick -- but let's keep the discussion within the realm of possible reality. Chicago's weather extremes are a good starting point. Three examples: 109 degrees (July 23, 1934); 23.0 inches of snow (Jan. 26-27, 1967); dew point of 83 degrees (July 30, 1999). And for an answer to your question, we'll defer to Chicago weather historian Frank Wachowski who once remarked, "Weather records are made to be broken." There it is: Every standing weather record, given sufficient time, will fall.
When most Chicagoans think of the start of spring, warm temperatures,
flowers in bloom and the chance to shed winter coats come to mind. But
the reality of March's often quirky weather is that these idealized
images occur far less often than most here care to think. Instead, in
their place Saturday will be substantially lower temperatures, blustery
northeast winds and precipitation which has transitioned from liquid to
crystaline form. Snow is likely to have been falling a number of hours
by the time spring 2010 gets underway as the sun's most direct rays
cross the equator far to Chicago's south at 12:32 p.m. Saturday. That's
the moment astronomers refer to as the "vernal equinox"---or astronomical start of spring.
A storm system of Saturday's predicted intensity would have been
expected to produce 5 to 10-inch accumulations only a few months back.
But, the abnormally mild temperatures of recent weeks---March is
running more than 5-degrees above normal and 2010 is 2-degrees ahead of
the same period a year ago---have helped warmed the ground while, at
the same time, boosting Lake Michigan water temperatures off of which
Saturday's gusty north to northeast winds are to blow. Shoreline water
temperatures are running 3-degrees higher than this time last
year---42-degrees versus 39 degrees. Factors such as these play a
decisive role in determining how much of any late-season snow which
falls is able to stick.
An average of the 43 most recent computer snowfall projections for the
upcoming weekend works out to about 5 inches---though individual
predictions range all the way from 0 to 9.3-inches. It's not wise to
read too much into these stats just yet. It's likely far less than
these amounts will actually end up sticking---but, if snow were to fall
heavily amounts in the upper end of such a range couldn't be ruled out.
It appears at this distance that the potential for some slushy
accumulations on colder outdoor surfaces is possible in this system
especially inland---away from the warmth of Lake Michigan Saturday and
Saturday night.
Winter storm prompts warnings across 10 states; could send some Oklahoma seasonal snow tallies to all-time records
Concerns over the developing storm system prompted the issuance of
winter storm watches and warnings across sections of 10 states to
Chicago's west and southwest late Thursday. Early indications suggest
sections of Oklahoma, Kansas and western Missouri may bear the brunt of
the storm's snowfall with accumulations possibly totaling 6 to 10
inches. Were such an accumulation occur in Oklahoma City, it would
push the current season tally of 20.7 inches to a new high---possibly
breaking its all-time seasonal snow record of 25.2 inches set in
1947-48.
Sections of Florida shiver shiver through chilliest winter on the books
New all time records for the chilliest winter temperatures are about to
be set across sections of Florida. Readings since Dec. 21---spanning
the so-called "astronomical winter" period--- have averaged
55.8-degrees at Orlando, falling below the previous all-time low of
56.9-degrees. Orlando weather records span 65 years. Other Florida
all-time low winter temperature averages include 56.6-degrees at
Melborne and 57.6-degrees in Vero Beach.
Dear Tom,
How does the lack of subzero weather this season compare with past years?
--Greg Pracz, Westchester
Dear Greg,
So far this season, Chicago has recorded one subzero day, a low temperature of 1 degree below zero on Jan. 3, and with March 22 as the date of the city's latest ever subzero reading on the horizon, it appears that lone day will represent the season's final count. Since late 1870, the city's long-term average for subzero days is around eight, so this winter is definitely on the low-end of the spectrum. There have been only 12 cold seasons that failed to produce a single subzero day, the last one being the winter of 1982-83.
The opening decade of the 21st century has produced only 49 subzero days in Chicago, the lowest decadal total since the 1930s, which produced only 46. The 1980s take the honors for the most subzero days with 119.
March is to put on quite a meteorological show in coming days, strutting the weather of two distinctly different seasons before Chicagoans over a span of just days. Unseasonable warmth Thursday and Friday---including the year's highest daytime readings to date---is to yield to a wintry temperature downturn this weekend which may well set the area up for wet snow. It's sure to be a jarring change for many in the Chicago area with the wintry tone of the weather shift in conflict---at least in spirit---with spring's 12:32 p.m. Saturday arrival.
The year's mildest temperatures are due first---including a possible 70 degree high Thursday. It's a development which would propel this month into the ranks of the 70 percent of Marches over the past 140 years which have produced a 70-degree temperature. Not since a 73-degree high on Nov. 8 has the mercury warmed to that level here. The production of such warmth this early in the season always depends on the perfect alignment of a host of factors. West winds must overcome the tendency for the 2,000 ft. deep dome of cold, dense air, which hugs the chilly lake surface this time of year, to surge inland. And clouds must not seriously screen out sunlight which is especially critical in producing early season warmth.
It appears both conditions will be met Thursday---though the wild card will be high clouds expected to move across area skies as the day proceeds. Air sinking on a broad scale beneath a band of powerful jet stream winds is expected to produce enough warming to offset at least some of the impact of these clouds.
A 70-degree temperature would come one week earlier than the most recent 50 year average date of March 24 and nearly a year to the day of last year's first 70, which occurred last St. Patrick's Day.
Set-up behind Chicago's Thursday warm-up produced high winds, record-breaking temps in Montana
Sinking air beneath the same pocket of powerhouse jet stream winds expected to traverse Chicago airspace Thursday and Thursday night, helped produce record highs and powerful downsloping winds in Montana Wednesday. Record highs resulted at Billings (73-degrees) and Miles City (71).
March 2010 more the 5-degrees above normal
Chicago's March temperatures are running more than 5-degrees above normal to date and more than 3-degrees ahead of the same period a year ago. That's warm enough to place its opening 17 days among the warmest 13 percent of comparable periods since 1871.
Models hint at sticking weekend snow here or nearby---but stay tuned
Computer models suggest sticking snow may accompany this weekend's temperature crash over at least portions of the Chicago area. A suite of 29 different model forecasts put average snowfall Saturday afternoon and night around 4 inches. But it's a forecast which is hardly carved in stone. Predicting accumulations in late season snow systems, particularly when they follow air masses as mild as the one in place Thursday and Friday, is extremely challenging.
109 of the past 125 years---that's 87 percent of them---have hosted accumulating snow beyond March 18. It's a sign winter isn't over yet.
Dear Tom,
What is the earliest date for the last measurable snowfall of a season in Chicago?
--Arleen Hambach
Dear Arleen,
It seems hard to believe, but Chicago's earliest last measurable snow has twice occurred in February. The earliest finish to a snow season was Feb. 27, 1997, when 0.5 inches of snow was measured. Beyond that only traces were recorded in March and April with the season's last flakes on April 13. Close behind was the winter of 1993-94 when the 0.8 inches that fell Feb. 28 was the season's last measurable snow. That year the final flurries were observed April 30. Despite the early end to those snow seasons, the seasonal totals were close to the city's average of about 40 inches. The winter of 1996-97 produced 40.6 inches while the winter of 1993-94 racked up 41.8 inches.
Bountiful St. Patrick's Day sunshine isn't to be the last in coming days. There's more great weather on deck---though there are also signs Chicago's weekend weather could become dicey with rain and even the threat of wet snow. Storms must be monitored closely this time of year. Their varied temperatures can take rain to snow despite a period of warmth. This storm's impact on the Chicago area is still days away and will depend on a variety of factors including its future track.
Snow is to be the last thing on people's minds Wednesday. Temperatures surged past 60-degrees Tuesday-- topping out at 61 at O'Hare and as warm as 69 at Elgin, 68 Itasca and 67 in Oswego and 66 at Blue Island. These readings are 18 or more degrees above normal---and Wednesday looks even warmer. The 65 predicted at O'Hare Wednesday afternoon would immediately become 2010's warmest to date and would arrive nearly a year to the day of last year's first 70-degree reading---a 74-degree high which occurred on today's date in 2009.
But it's Thursday which stands a good chance of becoming the warmest of the current mild spell. That's when the city's official high is predicted to move to within striking distance of 70-degrees. Large scale subsidence of air beneath the incoming nose of a powerful jet stream is to combine forces with Thursday's generous sunshine and strong west winds capable of overcome lake cooling to produce the first 70-degree reading of 2010 nearly 4 months after the Chicago area's last 70 on Nov. 8.
Warm weather isn't surprising this time of year nor is it mis-timed. In the past decade, March 22 has been the average first date for a 70 here---and March 24 has been the average over the past half century of readings at O'Hare.
Tuesday becomes one of only 10 days in the past 140 years with relative humidities in the teens
Remarkably low relative humidities (RH) across the metro area played a role in producing Tuesday's warm highs. Dry air heats expeditiously. A plunge in RH readings observed just after noon Tuesday coincided with rapid warming. The appearance of low humidities occurred as winds helped mix exceptionally dry air, which had hovered just above the surface since Monday, down to ground-level.
Chicago recorded 90 percent of its possible sunshine Tuesday bringing the March average to 43 percent---52 is considered "normal" here in March.
Windy Seattle storm could head toward the Midwest
The storm system which may impact the Midwest this swept hit Seattle and Pacific Northwest with 60+ mph winds Tuesday, forcing bridge closures and producing power outages. It produced wind gusts of up to 69 mph at Tatoosh Island WA and 46 mph gusts in Seattle proper. At least 6,000 were reported without power in the region.
Despite the unseasonably mild weather predicted in Chicago over coming days, the weekend storm is to bring rain to the area which could mix with or change to wet snow Sunday. March in Chicago has never closed without at least a trace (0.1 inch or less) of snow.
Dear Tom,
It seems that it is usually cold on St. Patrick's Day. How often has it been 60 degrees or higher on that day?
--Nick Recchia, River Grove
Dear Nick,
Typically St. Patrick's Day brings highs in the middle or upper 40s, but there have been some stunningly warm exceptions. Just last year the mercury soared to 74 degrees, tying the record high for the day first logged in 1894. There have been two other St. Patrick's Days when the mercury topped 70 degrees -- in 1966 and 1973 when the high reached 73. The warmth in 1966 was a payback for a cold and snowy March 17 the year before when 3.7 inches of snow whitened the city. Seven other St. Patrick's Days have recorded highs in the 60s. There also have been some really cold Irish celebrations, including in 1941 when the high reached only 11 degrees and in 1900 when the early morning low was 1 degree below zero.
Temperatures across the Chicago could reach new 2010 highs later this week---a warm-up which may include 70-degrees (or a reading awfully close) Thursday and possibly Friday. It's a development which, by historical standards, is close to being on schedule. A 70 Thursday would come almost a year to the date of last year's first 70 on St. Patrick's Day (74 degrees on March 17) and only a week earlier than the March 24 average date of Chicago's first official 70 since readings began at O'Hare Field in 1959.
March sunshine plays a big role in sending temperatures higher this time of year. It arrives more than two and a half times stronger than December sunlight. Longer days and a daily trek across the sky more directly overhead are behind the strengthening.
While Monday's high stalled out at 48-degree under a heavy overcast, Tuesday's increased sunshine is to propel readings to the mid 50s---even a bit higher in warmer inland locations. Northeast winds will limit shoreline warming by delivering those areas lake-cooled air faster than the day's sunshine can warm it. From Chicago's lakefront north to Zion, Waukegan, Kenosha and Racine, that means highs may struggle to get close to 50 degrees.
Temperatures surged across the Midwest Monday in sun-drenched areas. While cloudy Chicago managed its 48-degree high, Madison Wis., where sunshine emerged during the afternoon, hit 58-degrees. Duluth Minn. and Sault Ste Marie, Mich.---saw record highs of 60 and 63-degrees respectively under mostly sunny skies
The "real warmth" is due here Thursday and Friday.
Thursday's atmospheric set-up which offers the most compelling case for warming. Not only is sunshine likely to be bountiful and will well-developed west to southwest winds will override lake cooling, but Chicago is to sit beneath the nose of powerful jet stream winds. It's a region of the atmosphere in which air sinks, compresses and warms on a large scale. This setup has been known to boost surface temperatures.
Record rains drench Boston a second day; March tallies there top 10 inches
The latest storm to lash sections of the Northeast has produced some extraordinary rainfalls since Friday, whipping the area with hurricane-force gusts. The system comes just two weeks after the region was pummeled by a gargantuan snowstorm. Monday saw another 2.86 inches of rain fall at the American Meteorological Society's headquarters in Boston, Massachusetts. The WeatherBug site there has tallied 10.90 inches since March began---more than six times the historical average.
Cold air's on the move this weekend; storm potential being monitored
A warm-up, including temperatures close to 70-degrees in coming days, may be only one in a series of big weather swings which lie ahead. By this weekend, a system lifting northeast from Texas and running along a sharp temperature contrast zone, is the basis for the rain being predicted here Saturday. The system increases prospects colder air could sweep in to the area Sunday and could change precipitation in portions of the Midwest to snow.
Dear Tom,
It was snowing when my son was born March 17, 1965. How much snow actually fell that day?
Sharon Fabier, Lindenhurst
Dear Sharon,
You son was born during the 1965 St. Patrick's Day snowstorm that brought up to a foot of snow to north portions of the Chicago area, with the heaviest amounts in a band from Palatine to Deerfield. Snowfall from that storm was quite variable across the region. In the south suburbs, there was little if any snow but heavy rainfall produced widespread flooding. In the city, snow totals ranged from a little less than 4 inches officially at Midway Airport to around 7 inches at O'Hare International Airport. It was also quite windy with gusts to 52 mph at Midway and 44 mph at Joliet. The storm knocked out power to thousands, a result of the heavy wet snow and gusty winds
Chicago's March weather is known for its volatility and rapid temperature changes. Its temperature extremes span 100 degrees, the greatest of any month -- ranging from an all-time 88-degree high on March 29, 1986, to a low of minus 12 on March 4, 1873. The early part of the upcoming week will feature seasonably mild weather with highs reaching the lower 50s away from Lake Michigan, but persistent north to northeast winds will keep a prevailing chill in the city and lakeside areas where temperatures will remain in the 40s. A surge of warmer air will sweep readings into the 60s by Thursday and Friday ahead of a potent spring storm expected to spread showers and thunderstorms into the area by early Saturday.
Snowless March in peril
So far this March has been one of the few to reach the "ides" without at least an official trace of snow on the books -- and with mild weather through the week no snow is expected at least through Saturday. A sharp influx of cold air Saturday night and Sunday interacting with low pressure moving north through Indiana could not only bring Chicago its first flakes of the month, but also some accumulating snow if current forecasts play out.
Dear Tom,
The nation's lowest and highest temperatures on March 7 were in Angel Fire, N.M., and Fort Stockton, Texas--only 422 miles apart. Historically, what is the shortest distance between the daily national high and low temperature locales?
Dave Mesich, Streamwood
Dear Dave,
Because temperatures usually decline by 5.4 degrees for every 1,000 feet of vertical ascent, elevation is the key to an answer. Locations near to each other but at greatly different elevations are the likely candidates.
Steven Dutch, Professor of Geology at the University of Wisconsin-Green Bay, has painstakingly documented the nation's daily temperature extremes since 1995. His results indicate that Truckee (elevation 5,840 feet) and Death Valley (190 feet below sea level), both in California and 264 miles apart, occasionally register the nation's lowest and highest temperatures, respectively, on the same day.
Chicagoans endured a windy, wet and raw Saturday that put a damper on the city's early St. Patrick's Day celebrations. With temperatures hovering in the 40s and northeast winds gusting to nearly 40 mph, wind-driven rains officially totaled nearly 0.60 inches at O'Hare International Airport, but topped 1 inch in the harder hit south suburban areas. Sunday promises to be drier with just some sprinkles or passing light showers, but persistent clouds and northeast winds will continue the chill.
Chicago's weather was tame compared to the pounding out East. Areas from West Virginia and Pennsylvania to Connecticut were on the eastern flank of the same storm that brought Chicago its inclement weather Saturday. High winds and heavy rain produced flooding, downed trees and knocked out power to hundreds of thousands of residents while disrupting air and rail travel. Winds gusted as high as 64 mph in New York City while more than two inches of rain soaked Newark, New Jersey (2.16 inches) and Philadelphia (2.30 inches). The storm battered the same areas that were hit with a massive 2-3 foot snowstorm just two weeks ago.
Dear Tom,
I remember a big flood in the city in August 1987. Was the flooding caused by a series of strong thunderstorms or a frontal passage?
Robert Skurski, Chicago
Dear Robert,
That flood, one of the worst to ever hit the city, was caused by waves of moisture-laden thunderstorms that "trained" over areas from Rockford to Chicago's North Side for about 17 hours on Aug. 13-14, 1987. When the storms abated, 9.35 inches of rain had inundated the area near O'Hare International Airport, turning it into an inaccessible island for nearly 24 hours. The brunt of the storm targeted the north and west parts of the metropolitan area, causing three fatalities and damage in excess of $220 million. Wet weather continued to plague the city after the flood and August 1987 eventually tallied 17.10 inches of rain, making it the city's wettest month on record.
The inexorable seasonal march toward summer is on--but you wouldn't
know it to step outside Saturday. At best, it's a "march" which
proceeds in fits and starts--warm one day, chilly the next. The
temperature reduction, powerful 35+ mph gusts and spells of rain
sweeping the Chicago area Saturday may best be characterized as a
"fit"--rather than a "start."
The past week's all too brief
three-day excursion into the world of 50 and 60-degree temperatures is
history--for now. Warm-weather enthusiasts should take some solace in
early indications a spell of 60s may return for another comparatively
brief run later next week. Any prospect Saturday's dreary weather is
headed for the meteorological exit is being dashed by the onset of a
"blocking pattern" across Canada not expected to ease until next week.
Blocking patterns don't automatically mean all weather movement
screeches to a halt. But they often slow weather's progression,
allowing systems--like the weekend's blustery low pressure storm--to
linger.
Rainfall could approach an inch
Rain with
the current storm system arrived into the Chicago area from the
southeast--that's right, from the southeast--Friday afternoon. That's
opposite the movement of a majority of weather systems which tend to
arrive from the west or southwest. The storm's slow movement is to keep
the Chicago area shrouded by clouds and subjected to wind and sporadic
rain or drizzle through the weekend. Precipitation estimates vary--but
average to around 1 inch. It's the wind which many here may find most
objectionable. Varied pressures between the slow-moving storm downstate
and a sprawling Canadian high to the north will drive the gusty wind
regime. The set-up shows little sign of breaking down. Instead, its
demise is to be a slow one, suggesting its northeast to north winds
could still be with us into Wednesday--even though an injection of
drier air Monday should permit clouds to break and allow passing sun.
West Palm Beach walloped by over 5" of rain
It
was south and central Florida's turn for heavy rain Friday. Both coasts
of the often-sunny peninsula were subjected to wind-driven downpours
which totaled a record-breaking (for March 12) 5.28" at West Palm
Beach, 4.08" at Tampa, 3.67" at Ft. Myers and 3.21" at Vero Beach.
Storm gusts topped 40 mph.
A number of recent computer projections suggest sticking snow not out of the question in Week #2
Temperatures
are projected to rebound--possibly to the 60s--next Thursday and
Friday. But, a suite of longer-range computer models suggests fairly
strong cooling may follow. Projections into the 1-2 week time range
imply the cool-down may be strong enough to allow sticking snow in
sections of the Midwest--possibly not far from Chicago. It's a
development we'll monitor.
Dear Tom,
I know that days are getting longer, but is it in March that we gain the greatest amount of daylight?
--Pat Roberts, Lockport
Dear Pat,
It certainly is. March leads all months in daylight gain with an increase of 1 hour, 25 minutes during the course of the month. Runner-up April posts an increase of 1 hour, 17 minutes while February ranks third with a 70-minute increase.
When it comes to loss of daylight in the fall, October takes the honors with a decrease of 1 hour, 21 minutes, beating out September by just 1 minute.
On Sunday, when we turn our clocks ahead one hour as daylight saving time begins, the city will record 11 hours, 52 minutes of daylight, with sunrise at 7:04 a.m. and sunset at 6:56 p.m.
For a second consecutive day, spring warmth dominated Chicago's weather scene Thursday. In all but lakeside and some far north suburban locations, temperatures sailed back to 60-degrees and even higher in spots. By at 3:51 p.m. the reading at O'Hare had reached 60 degrees. Temperatures proceeded to 62 degrees at Midway with Marseilles, well southwest of the city, winding up with the area's warmest Thursday reading of 66-degrees. Kankakee and Oswego were close behind tallying 64-degree highs. The mild readings marked the first time since November a set of days produced back to back 60s.
Warming air has consequences in the world of meteorology and Thursday was no exception. As temperatures increase, air becomes buoyant and begins ascending, cooling in the process. That's precisely what happened Thursday. Add moisture to the mix while simultaneously positioning a pool of cooler than normal air aloft and thunderstorm development is typically not far behind.
That was certainly the scenario Thursday afternoon and evening. Doppler radar scans pegged northern Illinois and Indiana cloud tops at up to 35,000 ft. and reports of hail---much of it pea and marble-size---began arriving. Lightning data indicated the year's most impressive flurry of lightning activity to date with as many as 180 cloud to ground strokes in one ten minute early evening period. Lightning and small hail were still being reported by late evening---though it was clear nighttime cooling was allowing cloud tops to come down and the rate of lightning production to slow dramatically.
Mammoth storm to deliver strong winds and new rainfall starting Friday night
Big changes likely to set Chicago's weather on a wet, windy path won't be apparent right away Friday. The day is to open deceptively calm. Breaks in the clouds are likely to allow some sunshine to go to work on the air mass sending temperatures surging back into the 50s. But by late in the day Friday, the next wave of storminess is to begin making its move on the area. Clouds are to thicken and winds will begin increasing.
A formidable dome of mild air aloft is to assemble to Chicago's north. It's a development akin to building a dam across a river, forcing a northbound storm lifting out of the Gulf of Mexico to slow. By Saturday, winds through 40,000 feet of the atmosphere and from the Mid-Atlantic and New England west to the Nation's Heartland will be blowing vigorously from the east. Velocities of 50 mph or more are predicted several thousand feet above the surface and it's not uncommon for winds at that level to make it down to the surface as gusts---especially when winds are aligned through such a deep layer of the atmosphere.
Chicago-area wind velocities are likely to build fairly expeditiously late Friday or Friday evening and to be gusting to 30 mph by late Friday night and possibly to 40 mph at times Saturday. It's a development likely to make this year's St. Patrick's Day Parade a windy one in Chicago.
North Florida whacked by thunderstorms, local 5 inches rains
Powerful thunderstorms swept north and central Florida Thursday. Four reports of twisters were logged by NOAA's Storm Prediction Center while rainfalls topped 5 inches at Crystal River, Florida (5.34 inches) and a 4.82 inches rainfall was recorded in Ocala.
Dear Tom,
My husband is interested in the period of the year knowing when the sun reaches at least 45 degrees above the horizon. When will that take place?
Deborah and Neil Levin
Dear Deborah and Neil,
The noon sun in Chicago finally will reach an elevation 45 degrees above the horizon, the halfway point between the horizon and the zenith, on Friday.
Over the course of the year the highest daily sun elevation varies from a low point of 24.7 degrees on the winter solstice to a peak of 71.6 degrees on the summer solstice.
At 11:51 a.m. Friday, the sun will be at an elevation of 45 degrees and remain there for about 21 minutes. At 12:02 p.m. Sept. 30, the peak sun elevation will drop below 45 degrees and not regain that 45-degree peak until 11:36 a.m. March 13, 2011.
It's not every day Chicago's high temperatures sail past those of
Phoenix, Tucson, Las Vegas, San Diego and Los Angeles all at once---so
forgive us for taking a moment to relish the occasion. Highs of
62-degrees at O'Hare and 64-degrees at both Midway and the lakefront
made Wednesday the warmest day here in nearly four months. O'Hare's
full-day average temperature of 55-degrees was an eye-catching
20-degrees above normal. The city hasn't been treated to a daily
temperature surplus as large in nearly a year--since St. Patrick's Day
(March 17) a year ago.
Before 60s arrived Wednesday, comparably mild readings (60-degrees or
higher) hadn't occurred since last Nov. 14---nearly four months ago.
But almost as interesting was the fact Chicago area highs topped
readings in a number of perennially warm cities in the country's
Southwest. Wednesday's 61 degree highs at San Diego and Los Angeles,
the 58-degree high at Tucson, Arizona and a 56-degree peak reading at
Las Vegas all fell below our area's low and mid 60's.
The breadth of the warmth locally was stunning. Nearly four dozen of
the more than 200 communities with Weather Bug temperature sensors
across the greater Chicago area reported highs of at least 65-degrees
Wednesday. Among the warmest were 66-degree readings at Gary, Lansing,
Oswego, Itasca and Kankakee and 65-degree peak readings at New Lennox,
Willow Springs, Frankfort and, in Indiana, Valparaiso, Highland,
Schererville and Chesterton.
First the warmth, now blustery rains-some thundery
Waves of rain---some potentially thundery---are headed for Chicago
Thursday in the wake of the "warm" spell. A storm system with
thunderstorms, which bombarded sections of Oklahoma, Louisiana and
Arkansas Wednesday with barrages of hail and nearly half a dozen
twisters, is behind the rain threat in Chicago. The "lift" created as
the nose of powerful jet stream winds approach the metro area from the
southwest is to squeeze the nearly inch of evaporated water out of the
air producing the first of two rainy spells predicted to sweep the area
in the coming week. Computer model estimates of the total rainfall
these systems are to deliver between now and the end of the weekend
ranges from 0.40 inches to as much as 2.01 inches. While these are the
extreme values, the average of the 29 latest computer rain projections
is 1.55 inches---more than three times the 0.53 inches which typically
falls in a week at this time of year.
Second wet surge hits by Friday night, continues well into the weekend
A second vigorous wave threatens a new round of potentially heavy
rainfall later Friday or Friday night. The deep low pressure it induces
in combination with a sprawling Canadian high to the north sets the
stage for a windy weekend here. Winds blow---and do so
forcefully---when air pressures through the atmosphere vary greatly.
The predicted pressure variation between the next storm and the high to
the north Saturday and Sunday is to give rise to gusty east/northeast
winds expected to pump Atlantic moisture westward into the Midwest both
days, generating lots of clouds and waves of rainfall. Unlike
Wednesday, when south winds managed to extinguish lake cooling long
enough for temperatures in all but north lakeshore communities to soar,
the second storm system is to introduce gusty east to northeast winds
which take hold Friday afternoon---winds which are to continue over the
weekend possibly gusting to 30 mph Saturday and to 35 mph at times
Sunday.
Chicago weather records suggest 70 percent chance of a 70+ temp before March March's close
Weather records suggest that despite cooler winds off the lake
predicted in coming days, March has good track record at producing a
70-degree temperature sometime between now and the month's close. The
period has produced 70-degree or warmer highs nearly 70 percent of the
past 81 years at Midway Airport.
Dear Tom,
I have seen photographs of submarines pushing up through the sea ice at the North Pole, but has a surface ship such as an icebreaker ever made it to the Pole?
Stuart Levine
Dear Stuart,
Ice on the Arctic Ocean starts as frozen seawater, but it undergoes many changes as it ages, gradually becoming harder and more difficult to break and consequently nearly impossible for a surface vessel to push through. This is especially true of multi-year ice. Arctic ice also becomes snow-covered, and snow robs icebreakers of their forward momentum because of friction along the sides of the ship. Wind also pushes ice sheets into "pressure ridges" 25 to 30 feet above the water.
Yet despite the seemingly impenetrable nature of Arctic ice, the Soviet icebreaker Arktika, a nuclear-powered surface ship, rammed its way to the North Pole on Aug. 17, 1977, the first surface vessel to do so.
It's official! Today's temperatures have been the area's warmest in nearly 4 months. It's been a day which has delivered us the first official 60+-degree city temperatures since O'Hare's 63-degree on November 14 last fall. The city's official Wednesday highs were 62-degrees at O'Hare and 64-degrees at Midway. Temperatures first reached 60-degrees at the O'Hare observation site at 2:35 pm.
Here are some other area highs off some of our Weather Bug sensors across the metro area:
Henry 66 Gary 66 Lansing 66 Pontiac 66 Kankakee 66 New Lennox 66
Griffith IN 65 Itasca 65 Schererville IN 65 Munster 65 Chesterton 65
University Park 65 Buffalo Grove 65 Palos Heights 65 Flossmoor 65
Oswego 64 East Chicago 64 Blue Island 64
Lake cooled locations
Waukegan 49 Glencoe 53 Lake Geneva WI 54 Highland Park 55
Winnetka 56 McHenry 56 Fox Lake 57 Kenosha WI 52 Racine WI 48
Computer model rainfall numbers continue impressive over coming days. The first wave of organized rainfall begins later Thursday morning and continues in waves through Thursday evening. More rain and stronger, cooler northeast winds lock in Friday afternoon into Saturday--and even Sunday is showing signs of being showery. The latest National Weather Service "GFS" (Global Forecast System) model rain projections are 1.90" at O'Hare and 1.90" at Midway Airport through the weekend and the Weather Service's WRF model is kicking out 1.59" O'Hare and 1.49" at Midway. More on our Wednesday evening WGN News weather segments at 5PM and 9 PM.
Tom Skilling
Tuesday's 51-degrees---the first 50+ and warmest temperature here in the 98 days since Dec. 1---isn't likely to last long as 2010's mildest reading to date. Highs Wednesday appear poised to exceed it by 10-degrees, reaching the low 60s for the first time since a Nov. 14 high of 63-degrees nearly four months ago.
A 60+ degree high this time of year is actually late. The average date for temperatures at that level over the past 81 years at Midway Airport has been on or about Feb. 28. Last year's first 60-degree temp occurred a month earlier on Feb. 10, 2009 (61-degrees) and nearly two months earlier the year before on Jan. 6, 2008 (60 degrees.) It will be some time before a majority of high temperatures reach or exceed 60-degrees on a daily basis---on average, April 16. But with five of the past six months having posted temperature deficits, any sign of warmth is welcome and few in Chicago would turn the "warmth" away even if it was possible.
Getting early season warmth into this area intact is always a dicey proposition. The ground is often cold, if not snow covered, at this point of the year and and ever-present shallow pool of cold, comparatively dense air hugs Lake Michigan's still frigid waters ready to run roughshod over any fledgling early season warm air masses which aren't backed by powerful southerly winds.
A number of supportive factors appear ready to go to work Wednesday warming the area. The easterly winds of recent days are slated to become more southerly---especially in areas away from the lakeshore---once a northbound warm front trudges across the area. This flow is part of an expansive area of southery winds which extend from the Gulf of Mexico north to the Midwest. It's occurring on the east side of a sprawling and still developing area of low pressure over the Plains. These south winds have access to a large reservoir of warm air which pushed Tuesday temperatures to 77-degree at Little Rock, Arkansas, 75 in Dallas and 66-degrees at Oklahoma City; 60s managed to make it as far north as Gary, Indiana.
Winds take on a more easterly component Thursday, traveling into eastern Illinois and Wisconsin after a chilly trek over 36-degree lake waters. This should cool lakeside locations while allowing readings in the south and far western suburbs to return to the 50s.
Predicting atmospheric blocking pattern threatens to keep rains coming here for days
Rainfall projections produced by a suite of computer models for Chicago and covering the coming 2 weeks remain impressive. Estimates of precipitation from the nine most recent runs of the National Weather Service's global forecast model average 2.28 inches---nearly twice the 1.19 inches considered normal for a 14-day period time of year. A series of rain-inducing impulses rotating around a huge storm system predicted to slow as it becomes trapped over the Midwest and Mid-Atlantic on the south end of a Canadian "blocking pattern" aloft are driving the big rainfall tallies.
Rainfall should pick up in coverage and intensity Thursday and Thursday night and again later Friday night and Saturday---though spells of precipitation are expected to occur from time to time through the weekend and into next Monday once the wet systems take control.
2010 U.S. severe weather season quiet by recent standards
The 2010 tornado season has been a comparatively mild one---at least so far. NOAA's Storm Prediction Center has logged only 44 tornado reports to date this year compared to 86 by this time a year ago and 169 two seasons ago.
Dear Tom,
In April 1961 I went camping in southern Indiana. It snowed on Sunday and on the way back we were stranded in Indianapolis for two days. What happened?
--Dennis Cusumano, Winthrop Harbor
Dear Dennis,
You were caught in the biggest late-season snowstorm to hit Chicago and portions of northern and central Indiana. The snow was accompanied by winds up to 50 mph and created 10-foot high drifts, closing roads and stranding thousands of motorists. The snow must have come as quite a shock because Saturday's temperatures at your campsite were in the upper 60s. Thunderstorms hit overnight and by Sunday morning 2 to 4 inches of snow were on the ground. The heaviest snow fell between Indianapolis and Chicago with totals ranging from 5 to 9 inches; Chicago officially received nearly 7 inches.
Chicago temperatures last surged above 50-degrees---reaching 55-degrees at O'Hare and 56-degrees at Midway---on Dec. 1. In the three months since, no additional 50s have occurred in the city proper. South suburban residents were treated to 50s Monday--including 52-degree highs at Lansing, Kankakee, New Lenox and Valparaiso, Ind. But, a stubborn overcast and light breezes off the lake denied the city readings as warm.
Monday marked Chicago's 97th consecutive day below 50-degrees, its longest such streak in 31 years---since the winter of 1978-79. The string is to continue Tuesday in the city, but 50s are likely to occur again in Chicago's south and west suburbs.
Wednesday appears a different story. A break in the sub-50 streak appears on the way, even in the city. More southerly winds are to send peak temperatures well into the 50s in all but north lakeshore communities. There, a slight easterly component to south winds will bring the flow off Lake Michigan's chilly waters limiting highs to the low and mid 40s.
Dense fog forms over snowpack and along Lake Michigan
An area of dense fog, responsible for slashing lakeside visibilities under an eighth of a mile late Monday evening, was predicted to coalesce overnight with a second area of fog which had begun forming as post-sunset darkness settled over the Chicago area's most heavily snow-covered areas to the north and west of the city. The inland-moving, pea-soup-thick fog reached Oak Brook and Arlington Heights by late evening dropping visibilities there to near zero.
Fog forms when the air temperature drops to the dew point. The dew point is the temperature at which the air is holding all the moisture it can or, put a bit differently, the reading at which the relative humidity reaches 100 percent. It's the perfect threshold for fog development.
With dew points Monday evening which ranged from 33 to 43-degrees across the metro area, surface winds off the 33.5-degree lake waters sent temperatures tumbling to the dew points, laying the foundation for fog formation.
Early season tornado devastates the south side of Hammon, Oklahoma
An eastbound storm system, expected to deliver rain to the Chicago area late Tuesday and Tuesday night, spawned a single but damaging twister in Hammon, Oklahoma just before 6 p.m. Monday. Damage to four homes and a barn on the town's south side was extensive. The tornado took down trees and power lines as well.
1-2-inch rainfalls projected by computer models
The Chicago area is entering a wetter than normal period. Rainfall occurs this week in two waves---the first due late Tuesday into Wednesday morning and likely to total 0.25 to 0.50 inches. A second, and far more significant rain-generating system hits Thursday then slows to a crawl as a blocking pattern impedes its ability to expeditiously exit the area. The slowdown is expected to keep extensive cloudiness and waves of precipitation a threat through the coming weekend. This may prove troublesome for this weekend's St. Patrick's Day parade.
Daylight Saving Time returns this weekend
It's that time again. Clocks are to be turned ahead an hour this weekend (at 2 a.m. Sunday morning) as Daylight Saving Time returns. Daylight Time is to remain with us until early Sunday, Nov. 7.
Dear Tom,
I remember an old weather proverb: "If March acts like April, April acts like March." Has that been true in Chicago?
--Douglas H. Hanbury, East Peoria
Dear Douglas,
No.
Chicago's mildest Marches have been followed by milder than normal and,
in most cases, nearly snow-free Aprils. Chicago climatologist Frank
Wachowski tracked the city's five mildest Marches and found that every
following April was substantially milder than normal, led by April 1878
with an 8.8 degree surplus and April 1921, which was 8.3 degrees warmer
than normal. April snowfall typically averages about 1.5 inches, and
only the 6.9 inches that fell in April 1910 was significant with the
combined snowfall of remaining four Aprils a mere 0.4 inches. On the
flip side, Wachowski noted that four of the city's five coldest Aprils
came after below-normal Marches.
Dear Tom,
I seem to recall a March subzero reading in Chicago within the last 15 years. Am I right?
Steve, Plainfield
Dear Steve,
Subzero days in March are rare in Chicago with only 15 on the books since 1871, but you are correct that one did occur recently. On March 4, 2002, the mercury plunged to a frigid minus 7 at O'Hare Airport and minus 4 at Midway Airport, giving the city its first March subzero readings since 1982 when it dropped to 1 below on the 8th. Suburban areas were even colder with lows of minus 9 at Barrington, minus 12 at McHenry and minus 13 at both Romeoville and DeKalb. The coldest it's ever officially gotten in March in Chicago was 12 below on March 4, 1873, and the city's latest-in-the-season subzero reading occurred on March 22, 1888, when the thermometer bottomed out at minus 1.
The passage of a weak disturbance across the area today delivers clouds and showers, but it heads east, leaving a sun/cloud mix in its wake on Monday. Take note of Monday's sunshine, because it's likely we won't see the sun again until the weekend.
Lots of rain on the way
A large, complex and slow-moving storm system gradually organizes over the nation's midsection in coming days, the result of which is to be a four-day period of cloudy, wet and gloomy weather for Chicago. Rain that begins on Tuesday will continue intermittently through Friday. Daytime temperatures - mostly in the 40s - won't change much from day to day, but a persistent flow of wind off the 34-degree waters of Lake Michigan means readings probably won't rise out of the 30s within a mile or two of the lake.
Dear Tom,
Has Lake Michigan ever completely frozen over?
--Hannah Senne
Dear Hannah,
Ice development on Lake Michigan usually begins in January and it attains its maximum extent in late February or early March, so this is the time of year for such an event to occur. However, constant wind and wave action combined with the vast reservoir of heat contained in the lake prevents it from freezing completely, even in the harshest winters.
According to Environment Canada and the U.S. National Weather Service, lake ice coverage has reached 90 to 95 percent in the coldest winters, including 1903-04, 1976-77 and 1978-79. Though travel across the lake on ice is impossible, in very cold winters ice will form and bank up solidly along shore areas, making it possible to travel around the lake entirely on ice. This happened in February 1899 and was noted in a 1959 article in the Chicago Tribune.
Chicago's official thermometer at O'Hare International Airport peaked at 55 degrees on Dec. 1 and Chicagoans have not experienced 50-degree warmth since then. It was hoped that readings might hit 50 degrees this weekend, and that is still not out of the question in far south portions of metropolitan Chicago, from about Kankakee southward. For most of the area, however, 50 degrees this weekend is proving to be elusive. The combination of increasing afternoon cloudiness and the likelihood of cooling winds off Lake Michigan, whose water temperature is 34 degrees, will cap Saturday and Sunday readings in the 40s.
Looking to next week, a cloudy, cold and generally rainy weather picture emerges. Computer models indicate the development of a complex, sprawling area of low pressure over the mid-Mississippi Valley, and it is set to impact Chicago's weather negatively.
-- By Richard Koeneman, WGN-TV Meteorologist
Dear Tom,
Droughts were in the news a couple years ago. What is the status now?
-- Carlos Mendez
Dear Carlos,
Much of the United States experienced a withering drought in 2007 and 2008, and in portions of the Southwest, West and Southeast the drought began in 2005. At its worst in August 2007, 60 percent of the nation was in drought. In the Southeast, it was the worst drought in more than a century. Now, though, that figure has declined to 7 percent, according to the federal Climate Prediction Center. Douglas LeComte, a meteorologist with the center, says, "The lack of drought (now) is extraordinary." There have been fewer than a half dozen times since the late 1800s when drought has been as sparse as it is now. Even California, which experiences chronic water shortages, is no longer in drought.
March, Chicago's most volatile weather month, occupies the transition period between winter and summer, and its weather behaves accordingly. It has delivered temperatures as low as 12 degrees below zero (March 4, 1873) and as high as 88 degrees (March 29, 1986), and it has produced historic snowstorms (22.3 inches on March 25-26, 1930). Judged against those extremes and against March weather that is typically chaotic and highly changeable, the city's seven-day forecast is decidedly bland: moderate temperature swings and possibly two brief bouts of rain (Sunday and Wednesday).
Ice traps ships
Heavy pack ice in the Baltic Sea has trapped dozens of ships off Sweden's coast, including nearly 1,000 people aboard the ferry Amorella. Gale force winds were hampering rescue efforts, but no ships were in danger.
Dear Tom,
I have heard the full moon is 10 times as bright as a half moon, but this defies logic.
Milan Antilli
Dear Milan,
It's true. The moon has a rocky surface that shines only by reflected sunlight. The face is so deeply scarred and cratered that, as viewed from Earth, much of its surface is in shadow. Light reflected to our eyes is maximized when sunlight shines directly down on the center of the moon's face ---the only portion of the spherical surface that "looks" straight to us. During a half moon, only a poorly illuminated periphery of the face is seen. The view of the moon's face is best during a full moon, when the moon is in such a position in its orbit that the sun is behind us and the moon appears in the opposite side of the sky. That's when sunlight best illuminates the moon's deepest features and reduces shadows.
Thursday marks the 68th day that at least 1 inch of snow has covered the ground in Chicago during the 2009-10 snow season. That's the greatest number of days of snow-covered ground since the snow season of 1983-84, which logged 85 days of snow cover, but it's far short of the city's snow-cover record: 100 days of at least 1 inch of snow on the ground logged during the brutally cold and snowy winter of 1978-79. Lingering snow will disappear this week with temperatures climbing into the 40s.
Another cold Florida night
With expected wind chill temperatures as low as 30 degrees, much of north and central Florida (including such normally mild locations as Tampa, Orlando and Daytona Beach) lies under a wind chill advisory early this morning. In addition, a freeze watch has been posted for the south tip of the state late Thursday into early Friday.
Dear Tom,
Which March 1 was most "lion-like?"
Pepper Roberts, Park Forest
Dear Pepper,
You pose an interesting but hard question to answer. March 1 has produced its fair share of inclement weather and it is difficult to select any one as being the worst. In 2007, thunderstorms produced 1.09 inches of rain, including some freezing rain. In 1948, 4 inches of snow fell. In 1947, 4.6 inches of snow fell at the opening of a two-day storm that put down 7.4 inches of snow. In 1962, the mercury plunged to 5 degrees below zero. And in 1890, the high for the day was only 14 degrees.
On the lamb side, there have been some delightful March openings, the most noteworthy being in 1992 when gusty southwest winds and plenty of sunshine boosted the temperature to a record high 71 degrees.
A warming trend is under way, but the chilly air that has dominated the Chicago area for several days is only reluctantly yielding to higher temperatures. Each day's afternoon temperatures will climb a few degrees higher until readings reach the upper 40s this weekend. Sunshine returns Thursday and Friday, but more clouds arrive Saturday in advance of the next weather system that promises rain by Sunday.
Chilean quake shortens day
According to Richard Gross at the Jet Propulsion Laboratory, Saturday's earthquake has speeded the Earth's axial rotation and shortened the days by 1.26 millionths of a second. Some of the planet's mass shifted slightly closer to the planet's axis and its rotation quickened, just as ice skaters spin more rapidly 8when they pull in their arms.
Dear Tom,
What is the largest temperature forecast error that you are aware of?
Rick Burdsall, Palatine
Dear Rick,
Records of temperature forecast errors are not maintained. However, a forecaster who once served at Cheyenne, Wyo., recalls that the station maintained a checklist for weather factors leading to the onset of chinook winds (warming winds that can suddenly howl down the slopes of the Rockies). Frigid arctic air covered Cheyenne one bitter day in January and the afternoon temperature was 15 degrees below zero. Satisfied that a chinook would not occur and that arctic air would remain in place, the afternoon forecaster called for an overnight low of 25 below. An unexpected chinook developed that night and Cheyenne's temperature surged to 25 degrees above zero by morning for a 50-degree error within 12 hours of the forecast being issued.
Chicago's winters, even those that are relatively mild and snow-free, typically bring more than enough cold temperatures, cloudy skies and snowy days to make us impatient for the milder temps and sunnier weather of spring. Worse still, the meteorological winter (Dec. 1 through Feb. 28) just ended was more harsh than most. Its temperatures ranked among the coldest 32 percent of all Chicago winters and its snowfall (52.4 inches) landed in the snowiest four percent. And with only 33 percent of possible sunshine (versus a normal of 43 percent), it was the city's least sunny winter in 12 years. March, too, has gotten off to a cloudy and chilly start, but that's about to change. Higher temperatures and rain, not snow, are forecast in the week ahead. Wintry weather is not over for good -- we've had arctic blasts and big snows in March - but, in the short term, significantly higher temperatures lie ahead
Dear Tom,
Has Chicago had more 70-degree highs or subzero lows during the first week of March?
Pat Byrne Hoffman Estates
Dear Pat,
Both events are rare, but Chicago weather historian Frank Wachowski tells us subzero lows win by the slimmest of margins. Since 1871 the city has recorded 10 days with subzero lows compared to nine days with highs of at least 70 degrees. The tiebreaker was logged eight years ago when the mercury plunged to 7 below on March 4, 2002. Wachowski noted that the city failed to record an early-March 70 until 1974 when the mercury hit 71 degrees March 3 and a high of 80 March 4. In 1983, the city experienced a string of unseasonably warm days with highs of 73, 73, 75 and 70 from March 3 to March 6. Chicago's last encounter with early-March warmth was in 2000, with back-to-back highs of 70 and 78 on March 6 and 7.
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