Chicago, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

071
FXUS63 KLOT 222017
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
217 PM CST Mon Dec 22 2025

.KEY MESSAGES...

- Above normal temps are expected through Saturday and then much
  colder temperatures are possible early next week.

- Low chance (20%) for light rain through late this evening.

- A period of somewhat dreary conditions is shaping up Wednesday
  and Thursday with periods of drizzle and showers, low clouds,
  fog.

&&

.DISCUSSION...
Issued at 217 PM CST Mon Dec 22 2025

Main concern in the short term, tonight, is the potential for
some light showers or possible drizzle. The CAMs continue to
show very light precip through this evening but there are two
factors working against the precip, rather low dewpoints at the
surface and a somewhat shallow cloud layer. That said, have
included slight chance pops through this evening. Current cloud
bases in the 2kft-4kft range would not support true drizzle but
if cloud bases lower later this evening, then some drizzle would
be possible. There is also the potential for showers across
northwest IN later this evening but the bulk of anything that
develops here, looks to remain mainly east of the local area.

Temps will be slow to fall this evening and low temps by morning
will likely be dependent on when/if the low clouds clear out,
with a sharp cut off currently across central IA and MO. If the
low clouds clear out overnight, low temps may dip lower than
currently expected, which is mid 30s north to upper 30s
southeast. With some amount of sunshine expected on Tuesday,
between possible departing low clouds in the morning and
increasing mid/high clouds during the day, high temps in the
mid/upper 40s look on track with perhaps a few areas reaching 50.

The forecast for much cooler temps midweek over the past few
days appears to be on track as much of the 12z model runs have
continued with a more southern solution to the location of a
frontal boundary. The first weak wave will move across the area
Wednesday afternoon/night bringing a period of light
rain/drizzle to the area with the frontal boundary now looking
to push south of the cwa and then the next system and its
surface low developing near the local area and racing east late
Thursday night into Friday morning. This would keep the local
area in northeast flow. Thus have maintained the previous
forecast`s highs for Wednesday, around 40 north to upper 40s
south. Then the blended guidance is now actually slightly cooler
than the previous forecast for Christmas with highs in the
lower 40s north to lower 50s south and these temps may still be
a few degrees too warm.

One change to the forecast is now that the frontal boundary is
looking to be further south, this may limit the drizzle
potential across much of the area on Christmas. Maintained
patchy fog Wednesday night areawide, but for Christmas, have
only included patchy fog/drizzle in the morning and for areas
south of I-80. Still likely to be a cloudy day, but much lower
confidence for drizzle persisting through the day.

Temps remain tricky for Thursday night/Friday morning and
dependent on the exact track/timing of the second low noted
above. There could be a brief period where temps rise ahead of
the low and then fall once it passes but too much uncertainty to
make any changes to the blended guidance from this distance.
Precip chances look to rapidly increase Thursday evening into
early Friday morning with likely pops reasonable. Temps will be
sufficiently warm to support all liquid precip across the local
area. There may also be a few thunderstorms on the south side of
the system, potentially across the southeast cwa but confidence
for thunder too low for mention at this time.

Beyond this time period, there still appears to be good support
for a strong cold front to move across the area Saturday night
into early Sunday morning and after highs in the 40s, possibly
lower 50s on Saturday, temperatures could be falling through the
20s on Sunday with northwest winds gusting 30-35 mph. Wind
chills could be falling below zero during Sunday afternoon as
well. Despite the good agreement currently, this is still
several days away and changes are possible. Made no changes to
the blended guidance, which did come in much colder than the
previous blended guidance. cms

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1215 PM CST Mon Dec 22 2025

Key Messages:

- MVFR ceilings are expected tonight, and a period of IFR
  ceilings is possible as well.

- A few sprinkles or spits of drizzle may be observed this
  afternoon and evening (~20-30% chance).


An expansive stratus deck is progressing northeastward towards
the terminals early this afternoon. MVFR-level ceilings largely
remain west of the Mississippi River at the time of this
writing, so VFR conditions are likely to prevail at the Chicago
metro terminals until this evening. RFD stands a better chance
to observe MVFR ceilings by mid-afternoon, but even those may be
temporary until the more solid push of MVFR arrives this evening.
As the deeper stratus arrives later this afternoon and evening,
it remains possible that some rain drops are observed at one or
more of our TAF sites, so have largely maintained the inherited
PROB30 groups that highlight that possibility. Still think that
notable visibility reductions from this activity are unlikely
to occur.

Later tonight, lowering inversion heights will cause the MVFR
stratus to build down and shrink in depth, which should end any
threat for sprinkles/drizzle by late evening. It is possible
that ceilings could build down to IFR levels overnight. However,
some erosion towards the backside of the stratus deck noted on
GOES visible satellite imagery early this afternoon does raise
questions about how prevalent stratus will be at this time, and
confidence in IFR ceilings being observed tonight remains
medium at best.

Regardless, a return to VFR conditions is likely by tomorrow
afternoon at the latest. A cold frontal passage tomorrow
morning will cause southerly winds to turn northwesterly, though
wind magnitudes are generally expected to remain near or just
below 10 kts through most of the current TAF cycle.

Ogorek

&&

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

&&

$$

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