La Nina is on its way in the equatorial Pacific, a development which increases the odds of a wetter than normal spring here and boosts the potential for an active Atlantic hurricane season.
Official confirmation of the transition to La Nina was issued by the National Ocean and Atmospheric Administration (NOAA) Tuesday. Computer climate models have predicted a rapid decline in Pacific ocean temperatures west of South America for some time. Predictions of that cooling have become even more emphatic in recent weeks signaling La Nina’s return. It was just months ago warmer than normal waters and weaker than usual easterly trade winds indicated the presence of an El Nino, which may well have contributed to our mid-winter warmth. Only one in 5 El Ninos dissipate as fast as this year’s.
A slight majority of the 23 La Ninas observed since 1946 have been accompanied by wetter than normal springs in Chicago.
--By Tom Skilling, WGN-TV Chief Meteorologist
Temperatures soared to 50° Wednesday on Chicago’s lakefront and at Gary. The warmth sent metro area temps above 40° a third consecutive day—the first time that’s happened since early January. Despite the recent string of above normal readings, this month is averaging only 13.5° making it the 6th coldest February on record here since 1871 and the coldest February in nearly three decades.
The chill has had a major effect on furnace usage. Estimates of home heating based on the month’s temps to date suggest usage has soared 36% in Chicago, a harbinger of significantly higher heating bills—a trend which has been observed across the entire Midwest.
The thick fog which preceded Wednesday’s warmth slashed visibilities to 1/16 of a mile just before 7am at Midway Airport and to 100 ft. in sections of northern Indiana, where a coating of frost covered trees and other cold outdoor surfaces.
—By Tom Skilling, WGN-TV Chief Meteorologist
Another low pressure “Alberta Clipper” system is headed this way out of the Dakotas. It should pass through Illinois tonight and early Saturday depositing a new 1 to 3-inch layer of snow over northeast Illinois. The last in a long series of almost continuous cold air surges out of Canada will follow, holding Sunday’s high temperatures in the teens with gusty northwest winds producing sub-zero wind chills once again. However a major shift in the jet stream is expected early next week with a west-east flow pattern expected to evolve over the United States, confining arctic air to central and northern Canada. A warming southerly flow will finally work it’s way back into the Midwest producing rain ahead of an approaching cold front later Monday and Tuesday. Despite very strong south winds, the extensive snow cover will hold temps in the low to mid 30s; however once rain is added to the mix, snows should melt quickly and rivers swell.
--By Paul Dailey, WGN Weather Center Meteorologist
The temperature in Chicago hovered at 0° as the first flakes of snow fluttered to earth around 8:35 a.m. Tuesday morning. Seven hours later, the hardest hit south and west suburban areas had measured up to 7" of snow, while 2.5" accumulated at Midway and 2.1" at O’Hare.
Snowfall at such low temperatures is “airy” and brings with it special challenges. Street chemicals, lacking additives to lower the freezing point of the water into which the snow melts, act more slowly. The meltwater produced can freeze in short order, complicating the flow of traffic. (Note: Chicago has added calcium chloride to its street salt since the late 1970s to combat snow accumulations which occur at low temps.) Also, the volume of such snow is often two to three times that of snow which falls at warmer readings. That’s why moisture which in warmer conditions would have produced just an inch or two of snow fluffed into a half a foot to the city’s south.
---By Tom Skilling, WGN-TV Chief Meteorologist
The Chicago area appears headed for its first 1"+ snow accumulation Tuesday since the 1.6" which fell Jan. 15. Snow is to commence toward midday and may fall 6-8 hours before ending Tuesday night. A small but fast moving disturbance racing southeastward is encouraging milder air to blow north into the formidable dome of cold air which has dominated here since Friday, a process often referred to as “overrunning”. Snowfall in air as cold as Tuesday’s tends to “fluff up” more than usual. That’s why the modest 0.13" (water equivalent) predicted to fall by a suite of computer models may lead to 2-3 times the normal volume of snow. Rather than a 1" snow, Tuesday’s system could put down as much as 1-3" across the city—less to the north but as much as 4-6" totals south to Kankakee and Morris.
Monday morning’s low reached -10° at O’Hare, the coldest temp since Jan. 5, 1999 when the low hit -16°.
--By Tom Skilling, WGN-TV Chief Meteorologist
An arctic front passed through Chicago Saturday morning setting the mercury on a downhill run that could end up rewriting a Feb. 4 record low max of 0° that has been on the books since 1918. Saturday’s temps peaked during the morning in the 10-15º range then fell steadily, dropping below zero by evening. The arctic air mass, one of the coldest in more than a decade, could keep readings here in negative territory at least until Monday afternoon and possibly until midday Tuesday. The city’s last encounter with subzero highs was 11 years ago (Feb. 2 and 3, 1996) with back-to-back highs of -5º. Exacerbating the cold will be biting west winds that will send wind chills tumbling to dangerous levels as low as -35º.
While the arctic blast in Chicago was accompanied by only brief flurries, total whiteout blizzard conditions were the rule in western Michigan Saturday where new snowfall totaled from 5-10 inches.
--By Steve Kahn, WGN Weather Center Meteorologist
PHOTO CREDIT: Gary Watson
PHOTO CREDIT: Dee Adams
PHOTO COURTESY: Bill Oswald
PHOTO COURTESY: Chris Neaville
