textproduct: Chicago

KEY MESSAGES

- Above normal temperatures through Saturday night, then turning much colder Sunday into early next week.

- Light rain/drizzle (70% chance) developing Wednesday afternoon and continuing into early Thursday morning. Areas of fog, possibly dense, also expected Wednesday night.

DISCUSSION

Issued at 204 PM CST Tue Dec 23 2025

High temps climbed into the upper 40s/lower 50s this afternoon with filtered sunshine through high clouds, making for a mild mid December day.

A frontal boundary will move across the area tonight, turning winds northeasterly. Soundings suggest low levels may stay mixed enough to prevent fog from developing, especially across the Chicago metro. Though with low temps expected in the upper 20s to lower 30s and below current dewpoints, some patchy/shallow fog is possible, especially across the southern cwa but for now have opted to have no fog mention in the forecast.

Models remain in good agreement for light rain/drizzle to develop Wednesday afternoon and continue into Wednesday evening and maintained likely pops. Wednesday morning will be dry and its unclear how much, if any sunshine may persist through mid morning, which may benefit warming temps, before skies become overcast. Considering where temps will be starting, opted to maintain the current forecast highs of lower 40s north to mid 40s south Wednesday.

Once the light rain/drizzle becomes widespread, fog will likely develop and persist into early Thursday morning and included areas of fog outside of the Chicago metro area and some dense fog is possible though confidence is fairly low. Trends continue to support any remaining drizzle tapering off from north to south early Christmas morning and have continued a dry forecast for Christmas with perhaps some morning patchy fog across the southern cwa. Also made no changes to high temps ranging from the upper 30s north to mid/upper 40s south.

The next system arrives/develops Thursday night with a chance of rain Thursday night into Friday morning. Temps currently appear to remain warm enough for all liquid rain for the local area, but could be quite the wintry mix just east of the area.

Blended guidance continues to keep Friday and Saturday rather mild with high temps mainly in the 50s with the usual cooler north, warm south gradients. These temps may end up being too warm, similar to the temps for Wednesday/Thursday over the past several days, especially if skies remain cloudy, but made no changes at this time.

Still very good agreement for much colder temperatures arriving Sunday into Monday, though one change is for a slower arrival of the cold front and colder air, likely due to a deeper surface low developing along the front and racing east Saturday night. Similar to the Thursday night system, current temp trends would support all liquid precip, if any occurs, before temps were to turn colder. Northwest winds still look strong with gusts into the 30-35 mph range Sunday, diminishing some Sunday night, but with subzero wind chills possible by Monday morning. cms

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/

Issued at 1140 AM CST Tue Dec 23 2025

VFR conditions are forecast through the majority of the period. WNW winds around 5-10kt will veer N to NE this evening and overnight then SE during the day on Wednesday.

There is a low chance (<20%) for sufficient low-level moisture to slosh west into the area early Wednesday morning which could lead to MVFR to locally IFR VSBY and/or CIG reductions, mainly out toward RFD. Have held off on a formal mention for now due to low confidence but will be something to monitor.

Increasing high cloud coverage is expected through the night with our next system arriving late Wednesday afternoon (~23-00Z) bringing a period of drizzle with associated lowering CIGs and VSBYs toward the end of (and especially beyond) the current 30-hr TAF period.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.