textproduct: Chicago

KEY MESSAGES

- Accumulating snow is expected late this evening through early Wednesday morning near and north of Interstate 80, with highest amounts (3-5") possible near the WI/IL state line.

- A strong Arctic front may bring a period of gusty snow showers Wednesday evening followed by patchy blowing snow overnight.

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

DISCUSSION

Issued at 327 AM CST Tue Jan 20 2026

We start off the morning under clear skies and bitterly cold conditions with wind chills in the -5 to -15 range across the area. A few lake effect flurries may linger through mid morning across northeast Porter county, otherwise dry conditions are expected through the afternoon. Increasing cloud coverage arrives later in the day ahead of an approaching clipper system. Temperatures will also moderate some today with highs in the 20s for most areas, with upper teens near the WI/IL state line.

The aforementioned clipper is expected to track southeast and across the region later this evening through early Wednesday morning. Model guidance has mostly converged on a narrow swath of accumulating snow developing across northern Illinois later this evening through the overnight hours, with the highest amounts favored near the WI-IL state line. A fairly deep layer of saturation situated within the DGZ paired with modest ascent within that layer supports a period of 0.5-1"/hr fluffy snowfall rates somewhere within the broader stratiform band). Have accordingly made upward adjustments in QPF and resultant snowfall amounts across far northern Illinois. While some wobbles in the system's exact track remain possible, in collaboration with neighboring offices, will be issuing a Winter Weather Advisory on this shift for the northern tier of Illinois counties where 3-5" of snow are forecast, in effect from 8 PM - 6 AM CST. Localized amounts within a narrow band approaching 6" are not out of the question (could be either side of WI/IL stateline). A shift to the south could warrant a southward expansion of the advisory with later updates. Will also have to keep an eye out on the potential for a southwest to northeast extension of the band to develop near and east of the I-55 corridor into early Wednesday morning as the system is exiting to the east, per the NAM/NAMnest/RRFS. If this were to occur, hazardous travel impacts could extend farther south and later into the morning commute.

Temperatures still look to warm closer to seasonable norms on Wednesday ahead of an approaching cold front with highs in the lower 30s south of I-80, lingering snow pack may hold temperatures in the mid-upper 20s north of I-80/88. Looking ahead to Wednesday evening, model guidance has trended toward a more robust arctic frontal passage across the area with stronger winds developing behind the front paired with gusty snow showers (and possible embedded squalls) along it. Have accordingly bumped of snow shower chances to "likely" (60%) for the evening hours near and north of Interstate-80 and increased wind gusts to 35 mph areawide with the potential for gusts to 40+ mph within any snow showers that develop. A quick 0.5-1" of snow could occur as it moves through, mainly falling within a 1-2 hour period (or less) at any single location. This will be a period to monitor closely in the event that it moves through during the latter part of the evening commute. Patchy blowing snow may then linger through early Thursday morning.

A second arctic front dives south across the area on Thursday which will usher in an extended period of bitter cold through early next week as surface high pressure settles across the region. Sub-zero low temperatures are forecast Thursday night through Monday morning for at least part of the local area, coldest across interior northern Illinois. Dangerous cold is looking increasingly likely for the Thursday night-early Friday AM and Friday night-early Saturday AM timeframe when minimum wind chills could drop into the -20 to -30 degree range.

We will also have to keep an eye on the winter storm expected to impact a large portion of the country to our south. While the more impactful snow and icing is favored to remain well south of the area, there are hints that the back edge of what could be a very expansive region of snow could brush part of the area over the weekend. Stay tuned.

Petr

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 525 AM CST Tue Jan 20 2026

Forecast concerns include...

Snow this evening through daybreak Wednesday. Possible south/southeast winds this evening.

West/southwest winds under 10kt will increase into the 10-15kt range this morning and continue into this afternoon. Winds will diminish toward sunset when directions will turn southerly and possibly become south/southeast for a few hours before turning back to the south/southwest overnight. Winds will shift back to westerly Wednesday morning when gusts into the 15-20kt will be possible.

Snow is expected to spread across northwest IL and RFD during the evening and then across the Chicago terminals in the late evening. There is still some uncertainty regarding the southern edge of the snow. Initially, the snow may favor areas just north of a DPA/ORD line, then more snow will spread or develop across the Chicago terminals overnight into early Wednesday morning. While confidence is low, opted to include prob mention for moderate snow and 1/2sm vis at ORD/DPA. This will need to be refined with later forecasts, but the potential warrants mention with this forecast. However, confidence is still low enough to maintain a higher vis at GYY/MDW for now. Further northwest, added tempo 1/2sm moderate snow at RFD and its possible there could be several hours of moderate snow at RFD. The snow will end from northwest to southeast around daybreak, perhaps persisting across northwest IN for a few hours past sunrise Wednesday morning. cms

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 from 8 PM this evening to 6 AM CST Wednesday for ILZ003-ILZ004-ILZ005-ILZ006.

IN...None. LM...Small Craft Advisory until 10 AM CST this morning for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.