DeKalb, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

931
FXUS63 KLOT 232335
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
535 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 /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 535 PM CST Tue Dec 23 2025

Key Aviation Messages for the current TAF period:

- Drizzle/light rain is expected toward the end of the TAF
  period with MVFR conditions

VFR conditions are expected through the overnight. As a weak
front moves through, winds will switch to the northeast tonight
and eventually to the southeast during the day tomorrow. There
is a less than 20 percent chance for low level moisture to move
inland overnight which would lower cigs/vis down to MVFR
levels. Given the low confidence, it was left out of the TAF but
will be monitored through the night.

Increasing cloud cover is expected through the day tomorrow,
and slowly lower to MVFR levels into the late afternoon. The
next system will pass over the airspace tomorrow evening.
Cannot rule out a brief light shower, but kept drizzle mention
being the prevailing precip type. MVFR cigs and vis are expected
with this precip. The probability of IFR conditions was too low
for any formal mention in the current TAF, but will need to be
re-evaluated in future TAF packages.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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