textproduct: Chicago

KEY MESSAGES

- Cold temperatures today before moderating back to near average through the weekend

- A slight (less than 25 percent) chance for light snow this afternoon for areas closer to the stateline and the lake.

- Slightly above average temperatures are possible next week

DISCUSSION

Issued at 209 AM CST Thu Jan 1 2026

Other than a few high clouds traveling southeastward out of Minnesota along the northwest steering flow, nighttime microphysics satellite imagery is showing clearing skies early this morning now that the front is far to the south. A colder air mass is oozing southward with most areas north of I-80 already in the teens. Temperatures will continue to drop this morning with single digits expected for areas north of I-88 by sunrise. Northerly winds remain between 10 to 15 mph providing wind chills near zero. There may be isolated lingering patches of slippery conditions on untreated surfaces from yesterdays precip. However, given the persistent winds, there are better chances that surfaces may have had a chance to dry out.

Another weak clipper system departing the eastern Dakotas is expected to pass nearby through the late morning and afternoon today. Models are in fairly good agreement showing the core of higher QPF with this system moving from approximately the Twin Cities through Milwaukee. There remains a mostly slight chance for northern Illinois to be grazed by this system as it passes. Cannot rule out a quick dusting for areas closer to the Wisconsin state line or Lake Michigan, but the best chances for minor accumulations would be in northeastern Lake County Illinois.

An upper level ridge will grow over the Great Plains Thursday into Friday. While weak northwest steering flow will remain through the weekend, the upper level low over eastern Canada weakening and moving eastward will help keep any new waves that come down the flow generally north of the forecast area. Only the NAMNest is suggesting a more southerly path pushing more moisture into northern Illinois, but still has too much dry air near the surface so it is likely resolving virga. With most members of the GEFS and Euro ensembles keeping the transit farther north, PoPs were kept dry.

Temperatures should moderate nicely through the weekend back to around seasonal average. As the previously mentioned ridge continues to build early next week, high pressure will spread over the region allowing high temperatures to climb slightly above average. GEFS and Euro ensembles are already hinting at mean high temperatures touching 50 for areas south of I-80, so the question becomes how far north can some of those warmer temperatures advect northward.

There is some disagreement in ensembles on how long the ridge will last early next week. The GEFS suite has it remaining through around the Tuesday/Wednesday timeframe before breaking down, whereas the Euro has it starting to erode earlier in the week. An earlier erosion would allow another weak wave to pass by and provide some rain early next week. However, at this distance, there is lower confidence in any meaningful precipitation given the pattern uncertainty. There is a chance that we could be heading for a drier stretch for the first week of 2026.

DK

AVIATION /12Z TAFS THROUGH 18Z FRIDAY/

Issued at 525 AM CST Thu Jan 1 2026

- Chance of a brief period of IFR VSBY in snow early this afternoon, mainly at ORD.

Quick moving upper level disturbance could result in a narrow band or two of some pretty robust snow this afternoon, especially near or north of the I-90 corridor. The snow band(s) may end up being only 10-20 miles wide, but underneath them it could snow hard for a short time. For now, introduced a PROB30 for IFR snow for all the Chicago terminals for early afternoon. Oncoming day shift will closely monitor observational trends and will likely be able to either remove the snow or transition to a TEMPO or prevailing as confidence increases in where the band(s) may set up.

Otherwise, look for VFR conditions the next 24 hours with fairly light west or northwesterly winds.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...Small Craft Advisory until 10 AM CST this morning for Calumet Harbor IL to Burns Harbor IN.

Small Craft Advisory until 3 PM CST this afternoon for Burns Harbor to Michigan City IN.