textproduct: Chicago

KEY MESSAGES

- A strong Arctic front will bring a 1-3 hour period of gusty snow showers (greatest coverage north of I-80). Winds gusting to 40+ mph may lead to patchy blowing and drifting snow through tonight where snow falls.

- A second Arctic front will usher in an extended period of dangerous cold Thursday night through early next week.

- An Extreme Cold Watch remains in effect for late Thursday night into Friday morning for areas near and north of Interstate 55, where wind chills may drop below -30F.

- Fluffy accumulating snow paired with cold temperatures may cause hazardous travel conditions late Saturday into Sunday.

DISCUSSION

Issued at 320 PM CST Wed Jan 21 2026

The primary weather concerns through the period include:

- Strong gusty snow showers this evening. Confidence high

- Dangerous cold Thursday night through Saturday. Confidence high

- Increasing potential for accumulating snow and associated hazardous travel late Saturday into Sunday. Confidence in specifics is low.

No changes have been made to the going Extreme Cold Watch, which is in effect for late Thursday night into Friday morning for a good portion of northern IL along and northwest of I-55.

In the near term, we continue to monitor the threat and timing of a period of strong gusty winds, along with accumulating snow showers/squalls this evening. Water vapor imagery depicts the next approaching impulse currently shifting east-southeastward into far southwestern MN/far northwestern IA. This feature is driving an accompanying surface trough and strong cold front eastward into western and central IA early this afternoon. As this feature tracks eastward into our area towards and after 6 PM this evening, a period of locally intense snow showers are expected as low-level lapse rates steepen in advance of the approaching cold front. This will particularly be the case near/north of I-80/I-88 to near the WI state line, where a quick 1/2 to 1" of snow could fall prior to 10 PM.

Also of concern this evening is the expectation for a couple hour "pop" of strong west-northwesterly winds (perhaps briefly gusting 40 to 50 mph, strongest south of I-80) as strong surface pressure rises (~5 mb/3hr) onset just behind the cold frontal passage. The main window for these strong winds will be in the 8 to 11 pm timeframe. While the strongest winds may lag the more intense snow showers this evening, the magnitude of these winds will result in blowing and drifting snow in areas that get accumulating snow early this evening across far northern IL. Accordingly, expect some adverse impacts to travel across northern IL due to reduced visibilities (briefly under a 1 mile) and snow covered roads, most notably near the WI state line. We can't rule out short-fused hazard products (advisory or even snow squall warnings), if needed.

Winds will ease gradually after midnight through daybreak Thursday, though westerly winds will remain breezy. Forecast highs on Thursday will be colder, with temperatures remaining in the 20s. Later in the day, the next (and more significant) Arctic front will drop southward across the area. This front will again be paired with some gusty winds, and possible snow showers, albeit with less coverage than that expected this evening. Blustery northwesterly winds (gusting up to 30-35 mph) in the wake of this front will usher in our dangerously cold airmass Thursday night, with plummeting air temperatures expected to fall several degrees below zero prior to daybreak Friday morning. When combined with the blustery northwest winds, wind chills early Friday morning will be as low as 25F below to 35F below zero (coldest in the current watch area near/northwest of I-55).

The center of the 1045 mb Arctic high will build into the Upper Mississippi Valley late Friday. This will result in gradually abating winds late Friday into Friday night, which in turn will support "some" minor improvement in the wind chills late Friday into Saturday morning. Our current Extreme Cold Watch only covers the most extreme cold through Friday morning. While some very minor improvement to the wind chill is forecast Friday afternoon as the winds begin to ease, dangerous cold will persist into Saturday as actual air temperatures remain at, or below, zero. Accordingly, following the Friday morning end time of the Extreme Cold Watch, a Cold Weather Advisory is likely to be needed through Saturday morning.

The next item of interest is the threat for accumulating snow sometime late Saturday into Sunday. A significant winter storm is expected to impact a large chunk of the central, southern, and eastern CONUS this weekend, and we will largely reside along and near the northern periphery of this storm. In spite of this, there continues to be signs that the expansive precipitation shield to our south may expand northward across our area sometime Saturday into Sunday. While model and ensemble guidance does continue to trend in this direction, it is important to note that considerable uncertainty continues with the specifics of this system. This is especially the case considering that some complex interactions are likely to occur with a few separate waves transitioning through the larger aggregate trough in the west. Nevertheless, if snow does end up making into our area, very cold temperatures will support high ratio (20+ to 1) fluffy snow which would make for widespread hazardous travel across the area through the second half of the weekend. Stay tuned!

KJB

AVIATION /00Z TAFS THROUGH 06Z FRIDAY/

Issued at 601 PM CST Wed Jan 21 2026

A quick-moving disturbance will bring periods of SHSN across the terminals this evening. An initial band of SN aloft is struggling to fully saturate to the surface, but should result in a brief period of MVFR to perhaps very briefly IFR visibility at onset prior to 01Z. A second axis of SHSN with more robust coverage and intensity is expected roughly in the 01-02Z window, followed by a final strong band of SNSH with a cold front in the 03-04Z window. Conditions are expected to vary considerably, with visibility ranging briefly down to 1/2SM or less in the strongest showers to P6SM between the showers. The showers also have the potential to produce gusts of 30 to 40 knots, particularly toward the end of the 01-04Z window, resulting in SNSQ conditions at some locations.

The cold front is expected to cross the Chicago terminals around 04Z. WNW/NW winds will gust around 30 knots behind the front and through much of the overnight hours, but especially for the first couple hours behind the front. During this time, SHSN coverage and intensity will diminish, ending by daybreak Thursday.

Expect W winds to gust around 20 knots Thursday morning and over 25 knots during the afternoon before an arctic front veers winds NW with gusts around 30 knots early in the evening. A narrow band of light SN or scattered SHSN with generally MVFR visibility may precede the front for a couple hours. Shallow MVFR stratocumulus with flurries will likely proceed the front, but limited saturation of the cloud layer is enough to maintain a dry post-frontal TAF at this time.

Kluber

MARINE

Issued at 320 PM CST Wed Jan 21 2026

A Gale Warning remains in effect for all of our nearshore zones tonight. Another formidable arctic cold front is slated to push through the region this evening, causing west- southwesterly winds to turn westerly/west-northwesterly and gust to at least 35 kts behind the front. Some potential for 40 kt gales exists as well, though confidence in this is only low- medium at this time. Gusts will gradually subside with time Thursday morning as the front and associated low pressure center progress eastward.

Some consideration may need to be given to a Heavy Freezing Spray Warning for our nearshore zones adjacent to Porter County, IN. However, at this time, it appears that the more significant heavy freezing spray risk will remain over the open waters of Lake Michigan.

Ogorek/Castro

HYDROLOGY

Issued at 258 PM CST Mon Jan 19 2026

Area hydrographs and ice spotter reports confirm that ice continues to develop and spread across areal rivers. Localized ice jams are already present along the Rock, Des Plaines, and Fox Rivers. Continued cold temperatures tonight and Tuesday will cause ice to continue expanding and thickening.

After a brief warm-up in temperatures to above 20 degrees on Tuesday-Wednesday, another push of bitterly cold temperatures will arrive Thursday night. As a result, the threat for ice jams including localized flooding will increase further toward the end of the week and through the weekend.

- NWS Chicago

LOT WATCHES/WARNINGS/ADVISORIES

IL...Extreme Cold Watch from late Thursday night through Friday morning for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010- ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032- ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

Wind Advisory until midnight CST tonight for ILZ019-ILZ021- ILZ023-ILZ032-ILZ033-ILZ039.

IN...Wind Advisory until midnight CST /1 AM EST/ tonight for INZ010- INZ011-INZ019.

LM...Small Craft Advisory until 7 PM CST this evening for the IL and IN nearshore waters.

Gale Warning until 6 AM CST Thursday for the IL and IN nearshore waters.

Heavy Freezing Spray Warning from midnight tonight to 10 AM CST Thursday for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.