textproduct: Chicago

KEY MESSAGES

- A strong Arctic front will bring a 1-2 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 has been issued for late Thursday night into Friday morning for areas near and north of Interstate-55 where wind chills may drop below -30F.

DISCUSSION

Issued at 340 AM CST Wed Jan 21 2026

After a burst of heavier snow across far northern Illinois and even in parts of northwest Indiana, snow has mostly struggled to fill in over much of the area early this morning. Still can't rule out the development of a secondary southerly band resulting in an additional dusting near and east of Interstate-55, but given impacts are not anticipated to be at the level of a Winter Weather Advisory, have accordingly cancelled it early. Still can't rule out some slick spots into the first part of the AM commute where roads are still partially snow covered and where any additional snow falls through mid morning.

With less snow having fallen overnight, temperatures today are anticipated to warm into the 30s near and south of I-88 (mid- upper 20s north). In fact, some areas well south of I-80 could touch 40 by this afternoon. Winds will become breezy out of the west southeast by this afternoon with gusts to 20-25 mph.

Attention will quickly turn to this evening when a strong Arctic front is expected to push across the area. This feature in question is currently progressing across northern North Dakota early this morning and is expected to race southeast with time toward the area through the day. While confidence in a short period of snow showers and gusty winds developing is high for this period, there remains uncertainty with their intensity. Steepening low-level lapse rates could support a short 1-2 hour burst of snow (and quick accumulations to 1") followed by a period of wind gusts to 40+ mph through the evening. This could be paired with blowing and drifting snow where snow does accumulate. Have elected to hold off on either a Wind Advisory or Winter Weather Advisory issuance on this shift and will let the day shift get one final look at things to determine which product best fits the message based on upstream trends (and if warranted).

Winds will ease gradually after midnight through daybreak Thursday, remaining breezy. Forecast highs on Thursday are in the 20s for most of the area with upper teens toward the Wisconsin state line. A second Arctic front then pushes across the area later in the day on Thursday. This could also be paired with some gusty snow showers, albeit with less coverage than this evening. Did introduce a formal mention of snow showers in the forecast with this update to account for this.

Temperatures are expected to plummet in the wake of the front Thursday night, potentially well below zero across interior northern Illinois. Winds could still be in the 15-25 mph range out of the northwest through the morning on Friday. Because of this, wind chills will have the potential to drop below -30F for portions of the area. Accordingly, have issue an Extreme Cold Watch for areas generally near and north of Interstate-55. Can't rule out counties on the southeast periphery of the Watch being converted to a Cold Weather Advisory instead of a Warning with later updates if temperatures trend a bit warmer than currently forecast, but the message for dangerous cold will remain unchanged for early Friday morning! While not as extreme as early Friday AM, wind chills may remain colder than -15F through Saturday morning across the region. Be sure to check on family members and neighbors regularly during this stretch of very cold air. Bundle up in several layers if you must head outdoors.

Lake effect snow may occur into parts of northwest Indiana in the wake of Thursday's front at times through Saturday. Confidence in the details at this distance remain low, but something to monitor for those in northern Porter County.

A major winter storm is expected to take shape to our south late week. There remains some uncertainty with the handling of a trailing wave diving out of Canada and how it interacts/phases with the southern system. This could lead to accumulating snow lifting as far north as the local area Saturday night into Sunday (currently 30-40% chance). The EPS remains the most consistent with this signal and will be something to monitor closely over the coming days.

Petr

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 1106 PM CST Tue Jan 20 2026

Higher-than-typical uncertainty regarding snow trends tonight exists owing to the combination of dry air and a significant northward trend in short range guidance which does not match ongoing radar and surface observations.

At RFD: Have the highest confidence of the 5 TAF sites. Prevailing IFR vsbys with steady light snow with a TEMPO group for 1/2 SM through 08z based on radar and observation trends appears appropriate. After about 08-09z, expectation is for snowfall rates to diminish as low pressure shifts northward, with snow tapering through about 12z.

At the Chicago-area sites: highly variable conditions are expected from site to site, with notably below-typical confidence in TAF specifics. Elected to move the prevailing IFR vsbys into TEMPO groups given the latest radar trends at ORD, MDW, and DPA. At GYY, have slightly higher vsbys given the expectation for drier air to play an increasing role with southward extent. A final burst of snow is possible at the Chicago-area terminals in the 11-14z timeframe as activity comes to an end.

Winds will turn W to WSW through Wednesday afternoon and will become gusty. A strong front will move through the area Wednesday evening. Have maintained PROB30 groups at the Chicago-area terminals for stronger winds and snow showers, and introduced prevailing light snow at RFD. Some guidance suggests a potential for winds to briefly gust beyond 40 knots, although there remains significant spread and uncertainty in the placement of the strongest winds at this time.

Carlaw

MARINE

Issued at 1106 PM CST Tue Jan 20 2026

Have issued a Gale Warning for all of our nearshore zones Wednesday night. Another formidable arctic cold front is slated to push through the region Wednesday 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

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...Winter Weather Advisory until 8 AM CST this morning for ILZ003- ILZ004-ILZ005-ILZ006-ILZ008-ILZ011-ILZ012-ILZ013-ILZ103- ILZ104.

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.

IN...None. LM...Gale Warning from 3 PM this afternoon to 6 AM CST Thursday for the IL and IN nearshore waters.