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

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Severe weather potential for northern Illinois grows

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A Severe Thunderstorm Watch is in effect for much of west central and southwest Wisconsin, a small portion of northeast Iowa and the extreme northwest corner (Carroll, Jo Daviess, and Stephenson Counties) of Illinois until 5AM CDT. At 1:45AM a line of thunderstorms from Central Wisconsin into northeast and north central Iowa was moving east at 35 to 40 mph. Heavy rainfall downpours of an inch or so in a half hour with localized flooding and winds 50 to 65 mph uprooting and breaking branches of some trees has been reported with some of the stronger thunderstorms.

Current indications, subject to change of course, are that the band of thunderstorms will continue moving east and sagging slightly south, meaning they could be tracking into northeast Illinois between 6AM and 9AM Sunday morning and while still packing a punch could be in weakening stages.

The outflow winds from these storms could set the stage for thunderstorm redevelopment in the afternoon ahead of an approaching cold front. The cold front is forecast to move through the Chicago area between 6 and 8PM Sunday evening with showers and storms moving east through northern Indiana at that time.

Severe weather potential for northern Illinois grows

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A Severe Thunderstorm Watch is in effect for much of west central and southwest Wisconsin, a small portion of northeast Iowa and the extreme northwest corner (Carroll, Jo Daviess, and Stephenson Counties) of Illinois until 5AM CDT. At 1:30AM a line of thunderstorms from Central Wisconsin into northeast and north central Iowa was moving east at 35 to 40 mph. Heavy rainfall downpours of an inch or so in a half hour with localized flooding and winds 50 to 65 mph uprooting and breaking branches of some trees has been reported with some of the stronger thunderstorms.


Current indications, subject to change of course, are that the band of thunderstorms will continue moving east and sagging slightly south, meaning they could be tracking into northeast Illinois between 6AM and 9AM Sunday morning and while still packing a punch could be in weakening stages.The outflow winds from these storms could set the stage for thunderstorm redevelopment in the afternoon ahead of an approaching cold front. The cold front is forecast to move through the Chicago area between 6 and 8PM Sunday evening with showers and storms moving east through northern Indiana at that time.


Thunderstorms moving into northwest and north-central Illinois

A Severe Thunderstorm Watch will remain in effect until 3AM CDT for extreme northwest Illinois, northeast Iowa and southwest Wisconsin.

 At 1:30AM showers and thunderstorms were moving southeast at 35 mph with the leading edge along the Illinois-Wisconsin border into northeast Iowa. Strongest storms were located in northeast Iowa, but all the storms appeared to be weakening somewhat. Heavy rains have been reported with the stronger storms and wind gusts in excess of 60 mph were recorded in northeast Iowa.

 If they hold together, storms should reach Rockford shortly after 2AM and the far western and northern suburbs of Chicago after 3AM.

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A touch of cold air returns later Monday night

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As a low pressure system approaches northeast Illinois, clouds thicken and scattered light showers are expected to break out Monday. Best chance of showers will be in northern sections of the metro area. The most significant impact from the low is expected to occur across Minnesota and northern Wisconsin, where up to 5 inches of new snow could accumulate Monday. Colder air will follow the front with strong northwest winds flowing over warmer southern Lake Michigan waters, triggering snow showers over northern Indiana and the southwest lower Michigan snow belt Tuesday. Temperatures moderate briefly Thursday before another cool-down next weekend.
 
Flooding along the Gulf Coast
A stationary front oriented west-east just south of the Gulf of Mexico coastline has dumped heavy rains over the southern portions of Louisiana, Mississippi and Alabama, causing widespread flooding. New Orleans reported rainfall of 5 to 7 inches Sunday. Another wave of heavy rains is expected to dump an additional 2 to 4 inches over that same area Monday and Tuesday. Dense fog has also seriously impacted driving conditions all along the Gulf coastline from Texas to the Florida panhandle.

Hazardous weather over northeast Illinois and northwest Indiana

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Due to a solid snow cover in the far west--northwest--and north suburbs, surface temperatures will hover near or just below freezing tonight. Strong warming is taking place aloft between 2,500 feet and 6,500 feet due to a 50-plus mph southwest wind that is pulling in air originating from the southern and central plains. Light rain falling from the warm layer aloft is passing through a very narrow band of below freezing temperatures near the surface with a glaze of ice forming on solid surfaces (ie untreated roads, streets, sidewalks). The Chicago National Weather Service Forecast Office has issued a Freezing Rain Advisory for the affected counties (view the latest map -- affected areas are in purple). Travel and outdoor activities could be very hazardous as this layer of glaze forms and persists through the night.
 
In the Chicago metro area and portions of northwest Indiana not under the Freezing Rain Advisory,  hazardous driving conditions could exist in cold spots, but the lack of snow cover makes a general warning unnecessary. Travelers in these areas should be on the alert in case they drive through a cold spot that has glazed over.
 
The band of rain will probably pass to the east after midnight. However, a cold front is approaching from the west and freezing drizzle has been reported along and ahead of the front in eastern Iowa and northwestern Illinois. The cold front is not expected to pass through the Chicago area until midday Sunday. As a result the freezing drizzle could continue after the rains let up later tonight and persist into the morning hours Sunday, until temperatures once again rise above freezing. After the cold front temperatures will again fall with snow flurries in the forecast.

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Slick start to the day in some parts of the Chicago area

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Several sections of the metro area and far suburbs may have some slick spots to start this Sunday morning. A mix of rain and spotty sleet and snow spread into northeast Illinois and northwest Indiana Saturday evening, and was expected to diminish and end sometime after midnight. The precipitation started out as rain, but because the air was extremely dry, especially in northwest Indiana, a process called evaporative cooling took place as the raindrops fell through the very dry air, dropping air temperatures below freezing and resulting in a wintry mix of precipitation. It could be slick in some spots early this morning -- even without precipitation -- wherever surface temperatures remain at or below 32 degrees.

Next surge of cold air hits Tuesday
Southerly winds, high temperatures in the upper 30s and rain on Monday will work on melting the remaining snow cover deposited by last week's storm. But a southward shift in the polar jet stream will swing winds aloft around to the northwest, allowing a surge of cold air out of the Canadian Tundra to flow into the Midwest and and western Great Lakes Tuesday. After Monday, Chicago's high temperatures will probably not climb out of the 20s again until Thursday.

Brief warm-up before storm hits midweek

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The last day of November will see Chicago's 27th record-setting consecutive day with above-normal temperatures. Warmer readings are likely Tuesday as southwesterly winds and abundant sunshine allow afternoon high temperatures to approach and even exceed 50 degrees at many observation points around the metro area. A cold front should pass through Chicago early Wednesday, followed by a sudden turn to colder weather with falling temperatures.
 
Winter hits Chicago full-force Thursday
Winter storm warnings are in effect today over the southeast corner of Arizona, the southern half of New Mexico and extreme western Texas. Snow accumulations of 5 to 10 inches or more are forecast for higher elevations with several inches of snow possible even over lower desert areas. Current forecasts have the storm tracking through southern Texas and then northeast through Louisiana, eventually connecting with the cold front in Ohio and western Pennsylvania Thursday. The intensifying storm will pull cold air from the Canadian Tundra south into the Midwest. Thursday into Friday Chicago will experience strong north winds, snow showers and wind chills in the teens.

Chicago's winter is just around the corner

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Tuesday marks the first day of meteorological winter (Dec.1-Feb. 28), and the following day winterlike weather is forecast to hit the metro area. After the sunny and mild Saturday when Chicago hit a high of 54 degrees and St. Louis came in with a 71 (just a degree below Miami, FL), the first three days of this week here are expected to average out about 5 degrees above normal. But the long-running mild trend that began in early November (the streak of above-normal temperatures reached 25 Saturday--tying the all-time record for November) will come to an abrupt end next Thursday. Low pressure moving northeast out of the southern Plains will merge with a cold front charging through the Midwest into the eastern Great Lakes, leading to a wintry mix over Chicago Wednesday with light rain changing to snow or flurries as temperatures fall.

A cold last half of the week
The first arctic air mass of the season will ride a strong northerly flow out of the Canadian Tundra directly into the western Great Lakes Thursday and Friday. In Chicago temperatures will fall into the 20s Wednesday night and fail to warm out of the 20s for the next two days, dropping into the teens overnight. With temperatures in the 20s and strong northwesterly winds gusting as high as 30 mph, Chicago's daytime wind chills will probably be in the teens both Thursday and Friday.

Long-delayed rain arrives Monday morning

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Very dry, cool northeasterly flow held off the incoming rain Sunday for a good portion of the metro area. A solid area of rain continually pushed northeast and tried unsuccessfully much of the afternoon to cross U.S. Interstate 80 into the western and closer-in southern suburbs, evaporating as it fell into the much drier air.

By Sunday evening rainfall amounts south of I-80 were on the order of a tenth to a quarter inch, while north of the I-80 corridor just a trace was reported. Overnight the air to the north was expected to gradually become saturated, allowing rain to reach the ground over much of the metro area by Monday morning.
 
Clouds and rain expected the first half of Chicago's workweek
As low pressure strengthens and moves slowly northeast out of Missouri into Illinois, clouds and extended periods of rain are likely in Chicago through Wednesday. Best estimates are that heaviest rainfall, perhaps as much as a half to three-quarters of an inch, will likely occur later Tuesday into early Wednesday. A break in the clouds is forecast later in the workweek with a warm-up over the weekend.


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