Chicago, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

944
FXUS63 KLOT 232004
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
204 PM CST Tue Dec 23 2025

.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.

&&

$$

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