textproduct: Chicago

KEY MESSAGES

- Patchy blowing/low drifting snow this morning.

- Isolated to scattered snow showers possible today with a point-based 20-40% chance for any measurable snow.

- Well below normal temperatures Wednesday night through the weekend, with the coldest period bringing minimum wind chills of about 10 to 20 below Thursday morning and Thursday evening.

- Additional chances for snow Saturday night-Sunday and again early next work week.

DISCUSSION

Issued at 240 AM CST Wed Dec 3 2025

The gusty south/southwest winds have resulted in low drifting snow blowing onto some roads early this morning. Added patchy blowing snow to the grids/forecast through 15z this morning, when winds will diminish some across the north and then across the rest of the area early this afternoon. Trends will need to be monitored for this end time and whether low drifting snow develops again later this afternoon into this evening.

A strong cold front will move across the area this afternoon into early this evening shifting southwest winds to the northwest. There is a low chance for snow showers along and ahead of this front and made no changes to the going forecast pops of 20-40 percent. The HRRR is the only model suggesting that if any precip were to develop, it could be in the form of some patchy freezing drizzle. With confidence low on whether there is actually precipitation today, no mention with this forecast, but trends will need to be monitored.

No changes to the forecast or reasoning for temperatures tonight through Friday morning. Main takeaway will be the wind chills which will be in the -10 to -15 range overnight into Thursday morning and again Thursday night into early Friday morning. There may be a few areas that dip to -20 for wind chills, but these are not expected to be prolonged or widespread. Warm air advection early Friday morning should allow temps to level off and then slowly rise toward daybreak Friday morning.

There continues to be high uncertainty for precip chances in the extended with some mention of blended chance pops from Saturday night through the middle of next week. The one trend that appears to be emerging is there could be a clipper parade next week, with the potential that one or more of these pass north of the local area, which would potentially allow temps to moderate some. If there is precip falling with what will likely be cold ground, some mixed precip would be possible, but way too much uncertainty from this distance. cms

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 529 AM CST Wed Dec 3 2025

Key Messages:

- Lingering IFR/low-MVFR CIGs expected to briefly lift/scatter across terminals early this morning, though MVFR is expected to redevelop mid-late morning.

- There's a 30-40% chance of snow showers midday through this afternoon. Brief localized IFR conditions possible with snow showers.

- Breezy southwest winds become breezy northwest behind a cold front this afternoon. Gusts 20-25 kts at times MVFR CIGs should eventually scatter out later this evening/overnight.

Surface low pressure was passing northeast of Lake Superior early this morning, with a strong cold front trailing across WI into central IA. Ahead of the front, southwest winds have been gusting 20-25 kts at times, but should ease a bit later this morning as the cold frontal trough approaches. Persistent IFR stratus currently lingers over parts of northeast IL/northwest IN, though the trailing edge (blocked from view in satellite imagery by higher clouds) appears to be roughly along a CMI- DPA-ORD-PWK line as of 11Z, drifting slowly east-northeast. Expect a brief improving trend for the Chicago terminals (latest at GYY) this morning before MVFR CIGs redevelop mid-late morning ahead of the approaching cold front.

Scattered light snow showers are expected to develop along/ahead of the front by midday and persist into the afternoon as the front pushes southeast across the terminals. Model forecast soundings do indicate a lack of deep saturation at least initially however, making confidence in snow showers lowest at RFD, and highest at GYY (and south of the terminals in general). Have maintained the inherited PROB30 mention for a few hour period until cold FROPA with brief IFR possible, though coverage may be relatively sparse.

Winds shift northwest behind the cold front later this afternoon, remaining breezy with gusts near/around 20 kts persisting through the evening hours (gusts may be highest after sunset when stronger low-level cold advection strengthens). With drier air moving into the area, should see MVFR CIGs eventually scatter, though a developing subsidence inversion may keep at least a SCT MVFR layer across the area overnight.

Ratzer

CLIMATE

Issued at 542 PM CST Tue Dec 2 2025

Updated at 250 PM CST Tue Dec 2 2025

Here are the current record low temperatures for Thursday into Friday this week:

Chicago Cold High Low Thursday 12/4 13 (1991) 0 (1893) Friday 12/5 4 (2005)

Rockford Cold High Low Thursday 12/4 7 (1991) -4 (1991) Friday 12/5 -5 (2005)

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES

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

Small Craft Advisory from 9 PM this evening to 9 AM CST Thursday for Winthrop Harbor IL to Gary IN.

Small Craft Advisory until 3 PM CST Thursday for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.