SEVERE WEATHER UPDATES: February 2007 Archives

These shots provided to us by Steve Bolich certainly capture the flavor of Sunday afternoon and evening's weather in Chicago. The weekend storm, which deposited 1.13" water equivalent precipitation at Midway Airport, including 2.9" of snow Sunday at the South Side site and a storm total of 4.2" fell on the northwest side at O'Hare, generated a real atmospheric cocktail—including sleet and snow which started in the city at 4:53 pm, reports official NWS-Midway observer Frank Wachowski, then turned to freezing rain and sleet and then ALL rain late Saturday night, before shifting back to heavy snow Sunday afternoon and evening. Other area 3-day storm snowfall totals included:

Antioch 11.4"
Bull Valley 9.0"
Crystal Lake 7.6"
St. Charles 7.0"
Mundelein 6.4"
Harvard 6.0"
McHenry 5.3"
Barrington 5.6"
Elgin 5.5"
Aurora 5.3"
Lake Village, IN 5.4"
Oak Brook 4.1"
Skokie 3.1"
Peotone 3.0"
Park Forest 1.2"
Valparaiso 0.8"

Many thanks to my CLTV colleague Mike Hamernick and our NWS COOP
Observers for contributing to this preliminary list.

NOte: Posted 4 pm Monday, February 26, 2007

Tom Skilling
WGN-TV Chief Meteorologist

The Chicago area was reeling after a veritable smorgasbord of winter weather blasted the region Saturday night with every type of winter precipitation imaginable. Snow was predominate in the northern suburbs, while areas to the south vacillated between freezing rain, sleet and snow. Thunder and lightning accompanied the precipitation early Saturday evening with reports of thundersnow across a broad area from Palatine to DeKalb, and from Aurora to Joliet. The southern suburbs also received considerable freezing rain with more than a half inch of ice wreaking havoc with trees and power lines while making travel treacherous.
Saturday evening’s onslaught was but the opening round of a late winter storm that is expected to last into Monday. As colder air wraps into the system, the precipitation should change to all snow during Sunday, continuing in waves of varying intensity into Monday before ending.

--By Steve Kahn, WGN Weather Center Meteorologist

Today's snow accumulation became the heaviest official February tally in 7 years the moment it passed 3" here this morning. And at mid-afternoon, the snow has intensified and become heavy. Visibilities have plunged to 1/4 mile within the 2 p.m. hour in heavy snow at O'Hare, Midway, Wheeling and Waukegan--all weather stations within reach of lake moisture which now appears to be getting involved with our winter storm in its most substantial way yet. I can tell you from personal observation that ice floes have collected against the Chicago Lake Michigan shoreline out to an estimated distance of a quarter to a half mile but that open water is visible beyond that. This suggests lake moisture isn't being inhibited from flowing into our winter storm's cold back side. With computer model wind trajectories indicating an increasing fetch (distance over water) to the wind through tonight and into Wednesday morning even as colder and colder air pours south and increases the vertical temperature decline--a process meteorologists refer to as "destabilization"---the potential for waves of lake effect snowfall continuing even as the "system snow" departs early Tuesday night grows. That suggests this storm's snow still has a way to go in areas of northeast Illinois and southeast Wisconsin adjoining the lake. Waves of lake-effect snowfall are therefore likely to continue tonight and into Wednesday morning in Cook and Lake Counties Illinois--and even longer in Lake County Indiana and ultimately the Indiana lake snowbelt. Farther inland (i.e. the Fox Valley, DeKalb, Rockford, and ultimately southwest in areas like Morris, Yorkville, Oswego, etc.), snow will taper off overnight as the storm system moves east. As always, lake snow represents something of a meteorological wildcard when it comes to final storm totals from the current system. It seems another one to three inches may fall across the area--but as much as 4-6" additional snowfall (from mid Tuesday afternoon into Wednesday morning) can't be ruled out. Chicago proper appears a candidate for such snowfall. By mid-afternoon Tuesday, reports into our WGN Weather Center indicate 3-7" is already down across the greater Chicago area and blowing and drifting is being reported at many locations. Downstate, drifts 6 ft. high are paralyzing an area of Indiana between Lafayette and Indianapolis not far from I-65. And I've just been emailed by the mother of a 7th grader who, with classmates, was at a school-related gathering in Springfield and due to return tonight. She's just been informed her daughter and other classmates have pulled into a motel in Bloomington and don't expect to leave until morning. Please check out the photos relayed to us from downstate Mt. Pulaski by National Weather Service COOP observer Chris Neaville. Chris' shots all too clearly illustrate the weather situation downstate where wind gusts have been clocked over 50 mph. (Peak gusts in Chicago have been clocked as high as 37 mph at Midway Airport and 35 mph at O'Hare). Gusts offshore at the Harrison/Dever Crib have reached 46 mph.

Frigid arctic air with sub-zero nighttime lows takes hold in the storm's wake and an Alberta Clipper system introduces the area's next chance of snow Friday night into a portion of Saturday--though nothing close to as significant as the current winter storm which has prompted winter weather advisories/warnings across sections of 29 states Tuesday.

Here are some preliminary snow totals at 3pm Tuesday:
5.8” Midway Airport (where it's snowing hard as of this weather blog post and Frank Wachowski reports 4" has fallen in the past six hours)
4.5” O'Hare
5.5” 95th and Dan Ryan
4" Oak Brook
6.5" Streamwood
7" Kankakee
7" Bonfield
3" St. Charles
Springfield, Illinois (as of two hours ago) 9.9"--a record breaking total for the date. The old record for this date had stood since 1978) Note: Spotters in the Springfield, Illinois area are reporting amounts approaching 11".

We'll update the challenging weather situation on WGN's Nine O'Clock News tonight.

- Tom Skilling, WGN-TV Chief Meteorologist

Winter's most potent storm yet is bearing down on the Chicago area. While flurries and light snow in advance of the developing system flutter earthward at times Monday afternoon and evening, steady storm-related snowfall appears likely to spread northeastward Monday night, reaching the city proper between 11 p.m. and 2 a.m. That's the point at which computer models saturate the atmosphere.

While north and west suburban areas were socked with local 15-17" accumulations on Dec. 1 (i.e. the Fox Valley and Lake, McHenry, DeKalb, Ogle and Winnebago counties among others included), Chicago proper and its southern suburbs haven't recorded a snowfall of that intensity. That's why this system will rank among the most substantial in terms of CITY snowfall of the past several years if current snowfall projections verify. Our analysis of 35 computer model precipitation projections over the past two days from 12 separate models indicates an average of 0.60" water equivalent is likely to be centered on O'Hare--more south and less to the north. Individual totals projected by the models have varied from 0.39" on the low end to as much as 1.00" on the high end, which offers some sense of the sort of range in storm totals which might fall. The vertical temperature profiles through this storm indicate the strong probability lake moisture is to become entrained in its already generous supply of Gulf moisture, always a hard factor to pin down especially this late in the season with ice floes having developed on Lake Michigan, which reduces the amount of open water interfacing with the atmosphere. Northeast winds will bring a lot of that ice back to the western end of Lake Michigan and this will no doubt impact the amount of lake moisture able to get involved in enhancing the storm's snowfall. Having said that, we still expect enough open water offshore to contribute to the incoming storm's moisture budget. On this basis and the model predictions we've analyzed, we're predicting accumulations which may range from 3-4" north toward the Wisconsin line to 6-10" across Chicago and areas west to 10-14" south, in areas like Kankakee, Morris and Rensselaer, Ind.

Full coverage tonight on our WGN-TV Nine O'Clock News, in the Chicago Tribune and on our blog. Any reports of snowfall can be forwarded to us (and would be greatly appreciated) addressing them to our Ask Tom Why e-mail box.

--Tom Skilling, WGN-TV Chief Meteorologist