Recently in SEVERE WEATHER UPDATES Category

Tonight's snow to wind down in a few hours...another storm to follow Thursday night-Friday

The snow will be gradually winding down across the Chicago area as the evening wears on with only flurries expected in the area by about 10 p.m. Through 6 p.m. storm snow totals were approaching 4 inches at O'hare and 3 inches at Midway. By the time the snow ends area most area totals should be in the 4-6 inch range.

Before this storm's snow is even cleared, forecasters are already taking note of another storm that threatens the Chicago area during the late-Thursday-Friday period. This storm will have considerably more moisture to work with than tonight's storm and temperatures will be warmer so the area could be facing a messy mixture of heavy snow, ice and even rain before it is over. Winter storm watches are already posted across southern portions of Wisconsin and Lower Michigan and may be issued for northern Illinois and the Chicago area by Wednesday morning.

Beyond that another snow threat looms late Saturday and Sunday followed by an arctic blast that could bring the season's first widespread subzero temperatures.

Stay tuned!!

Steve Kahn WGN-TV/Chicago Tribune Meteorologist

Lake effect snow has developed Tuesday morning ahead of the main "system snow" due to overspread the area this afternoon and continue Tuesday night

Lake effect snow has developed in areas along Lake Michigan Tuesday morning in advance of the main snow expected to be generated by the latest wintry weather system to affect the area this afternoon and tonight. Light easterly winds and the intense cold situated over and adjacent to Lake Michgian are to blame for the early onset of lake-effect snow in areas closest to Lake Michgian including the city of Chicago.

The amount of snow weather systems produce is linked in part to the temperature of the atmosphere through which their snowflakes fall. While most weather systems produce snow in a ratio of about 10 inches for every inch of moisture available to them, temperatures with the Tuesday/Tuesday night system are at levels which will approximately double the volume of snow which falls from the roughly 0.30" water equivalent moisture the current disturbance is to generate. It's likely this system will produce 15 or 20-to-1 ratio snow. In other words, snowflakes will be fluffier and have one and a half to two times the volume of most systems' snow here. It if for that reason, our accumulation predictions have been set at 3 to 6"--where in a warmer environment, a system with the same level of moisture available to it might be expected to produce only 3" of snow. Since the city and southern suburbs have yet to receive a 3" or greater snow to date this season (our northern and northwest suburbs already HAVE seen 3"+ snows)---the current system is to produce the city and southern suburb's heaviest snow to date this season. Weather updates will be issued as necessary.

Tom Skilling
Chief Meteorologist-WGN-TV/Chicago Tribune

Wind damage, rain, and even some hail in certain areas ... this is your Severe Weather Update!

Tom Skilling is tracking the powerful thunderstorms that have been sweeping across the Chicago area, with wind gusts of up to 62 miles per hour. The WGN Weather Center has received recent reports of damage from the storm in the Western suburbs, including wind damage, rain, and even some hail!

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Tracey Surface provides us this photo of Tuesday afternoon’s snow as it swept into Montrose Harbor earlier this afternoon. Many thanks Tracey! By late evening (5:30 p.m.), Chicago area snow tallies have reached the 2-5” range—including 2” at O’Hare, 3” at Downers Grove and our meteorological colleague Steve Kahn reports 4” is down at Arlington Heights. Chicago’s Midway Airport—where the mid-afternoon 2007-08 seasonal tally has risen to 49.7” (14.7” of it having falling in February alone)—is likely to have played host to a total of 50+” before the evening ends, says veteran Midway and Chicago weather observer Frank Wachowski. Frank also reports this snow, because of the cold temperatures in which it has formed and fallen, has a 22 to 1 snow to water ratio—indicating this snow has more than twice the volume of conventional snow here.

Radar (at 5:45 p.m.) is indicating a band of snow is approaching from the west—snow likely to be reinforced by lake moisture riding NE winds. So the snow’s not done as of this posting—but will end later tonight. It’s not the last snow likely to occur here in the coming week. Though glorious (and welcome) sunshine is due Wednesday—more snow is predicted Thursday (Valentine’s Day) night. The area’s lack of February sun is running at record levels. Only 12% of Chicago’s possible sun has occurred—February’s “normal” tally is 46%.

More on WGN-TV’s Nine O’Clock News Tuesday evening, on our wgntv.com “weather blog” and in Wednesday’s Chicago Tribune.

Tom Skilling
WGN-TV Chief Meteorologist

Photo courtesy: Tracey Surface, Chicago

We’re boosting our Chicago accumulation forecasts further, a foot or more of snow likely in parts of the city—much lighter amounts south

The early onset of snow suggests even higher storm snow totals are likely in the city. Expectations precipitation would start as a rain/sleet mixture in the northern suburbs due to a layer of warm air aloft have NOT materialized suggesting northeast winds have injected a layer of drier air in the lower atmosphere producing evaporative cooling there. That’s why snow has begun as soon as it has. This means assumptions that the first hours of this storm’s precipitation would come down as liquid or a mix must be updated and that moisture must be added to our predicted snow tally. As a result, it now appears likely 8-14” will fall from Chicago north and west. The presence of potential thunderstorms could lead to locally higher totals. Our latest in-house RPM (Rapid Precision Mesocale) model forecast now puts totals at 13” at O’Hare and 10” at Midway. The University of Wisconsin NMS model is even suggesting 12-18” totals in portions of northern Illinois.

Thus a major winter storm, by far this winter’s biggest to date, looks likely to produce serious travel problems well into Wednesday. We’ll update as new information becomes available.

Tom Skilling

Chief Meteorologist, WGN-TV/Chicago Tribune

As of 6:21 p.m. parts of our western suburbs have had as much as 4.5 inches of snow. The snow will continue for many more hours with the height of the storm expected during the morning rush hours. This could be the biggest snowstorm that we've seen this winter.

Tune in early to WGN-TV. Our morning news will have the latest weather and school closings as early as 4:30 a.m.

The tornado watch for the Chicago metropolitan area has been canceled. Scattered showers will continue overnight with some heavier rain and possibly more thunderstorms developing late tonight and Tuesday morning.

Steve Kahn WGN-TV Weather Center Meteorologist

ENTIRE CHICAGO AREA UNDER A TORNADO WATCH UNTIL 9 PM THIS EVENING

Fast-moving tornadic thunderstorms swept across portions of extreme northern Illinois into southeast Wisconsin this afternoon from north of the Rockford area to near Kenosha. The storms left a trail of damage from the Machesney Park area north of Rockford east northeast through Poplar Grove passing north of Harvard before moving into southeast Wisconsin causing damage near New Munster in Kenosha County. Two twisters were also sighted near the Kenosha County Airport.

The twisters damaged numerous homes, downed trees, transformers and powerlines. High winds were also reported with gusts to 80 m.p.h. at Hebron in far northern McHenry County. A semi was overturned north of Harvard. Hail also accompanied the storms.

The storms erupted in an unseasonably warm record-breaking air mass that sent the mercury in Chicago to a balmy 65º shattering the day's previous record high of 59º set 101 years ago in 1907.

The entire Chicago Metropolitan area along with northwest Indiana remains under a tornado watch until 9 p.m.

Steve Kahn WGN-TV Weather Center Meteorologist

Severe thunderstorms developing rapidly, hail in the Loop

Marble size hail fell in the Loop on Michigan avenue and 60 m.p.h. wind gusts measured by the WeatherBug sensor atop the LaSalle Bank Building this evening just after 5:30 p.m. as severe thunderstorms rolled northeast into the city from the Joliet area. Shortly after
5:45 p.m. golf-ball size hail was reported in Joliet and winds gusts to 75 m.p.h. were clocked at Wilmington in Will County.

High winds blowing from the southwest, not associated with thunderstorms but directly related to the intensity of the storm system sweeping the Midwest have been raking the Chicago area throughout the afternoon and evening hours.

Some of the highest wind gusts are recorded on our WeatherBug network include
Tonti Elementary School Chicago 53 m.p.h.
Curie Metropolitan High School Chicago 52 m.p.h.
Simeon Academy Chicago 52 m.p.h
Bednarcik Junior High Aurora 51 m.p.h.
Gale Academy Chicago 50 m.p.h.

Steve Kahn WGN Weather Center Meteorologist