WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.

Dailey: May 2009 Archives

Just wait, and the weather will change over the metro area today. A cold
front will move through northeast Illinois preceded by showers and
thunderstorms. Strong storms with localized heavy downpours will pass to the
north this morning, and then a more organized band of showers and
thunderstorms should develop along the frontal boundary as it moves south
through the area this afternoon. Behind the front, winds shift to the
northeast bringing much cooler air off the 50-degree surface of Lake
Michigan. Further to the south ahead of the front, strong, possibly severe
storms will develop in moisture-laden 80-degree air.

More rain Tuesday

The cold front will become stationary south of Interstate 80 Tuesday with
resultant showers and thunderstorms likely to produce additional heavy rains
and possible flooding over northern Illinois. A slight shift in the jet
stream should move this weather system well to the south Wednesday, allowing
a drying-out period the rest of the workweek. Showers and thunderstorms may
return to the Midwest this weekend.

Frost and freeze warnings in the Northeastern U.S. tonight

A very cool Canadian-source high pressure air mass will sit over the northeast tonight. With clearing skies and light winds, a late season frost/freeze is expected over a large portion of the northeastern U.S. as temperatures are forecast to drop into the lower 30s early Monday morning from Maine to northern Pennsylvania.

Warming starts today in Chicago-peaks midweek

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As the upper-level jet stream flow eases north to the Canadian border, southerly flow returns to the Midwest and western Great Lakes. A cold front will tease Chicago as it slides south over Wisconsin and Lower Michigan Tuesday. The relatively smooth surface of Lake Michigan may allow it to progress further south into Chicago later Tuesday afternoon, but its incursion should be brief. By Wednesday strong southerly flow is expected to change the characteristics of the cold front to that of a warm front, pushing it back north over the same area it passed going south on Tuesday. Highs are expected to warm into the 80s for only the second time this year on Wednesday and probably exceed that mark again Thursday, before a stronger cold front brings much cooler air to the region Friday.
 
Frost warnings over Northeast U.S. early Monday
The coldest portion of the Canadian high pressure air mass shifted east Sunday and National Weather Service Forecast Offices had frost and or freeze warnings in effect for Monday morning over portions of Ohio, Kentucky, West Virginia, Pennsylvania, New York and Vermont.  
 
Good drying weather here this week
Showers and thunderstorms Tuesday and Thursday are expected to be widely scattered, and good drying conditions should occur for the most part, especially south of the metro area.

Cool Sunday, but big warm-up begins Monday

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With cool Canadian high pressure over the Midwest and Great Lakes, temperatures over northeast Illinois will be hard-pressed to hit 60 degrees today. It's been almost three weeks (high of 55 degrees on April 29) since the mercury last failed to reach at least 60-degrees at Chicago's official O'Hare airport observing site. As the high pressure air mass drifts east, southerly flow will return on Monday, allowing readings to rebound to normal levels. A cold front could sink south through the metro area later Tuesday temporarily shifting winds to the east off Lake Michigan. But indications are it will move back north Wednesday allowing daytime highs to warm into the 80s for just the second time this year. A stronger cooling high pressure system should push the cold front well south of the area later Thursday.
 
A letup in rainfall this week
 
With northeastern Illinois soils saturated due to the wettest spring on record, farmers are still looking for an opportunity to work their fields. While showers are forecast Tuesday and Thursday, the dynamics of the storm-triggering fronts as well as available moisture point to lesser amounts of rainfall and a seven-day period of above-normal drying conditions.