841
FXUS63 KLOT 040856
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
256 AM CST Wed Nov 4 2026

.KEY MESSAGES...

- Periods of scattered showers are expected at times into
  Friday, most notably Thursday and Thursday night.

- Breezy and cooler weather is expected through Friday.

- Potential for freezing temperatures across portions of the
  area Friday and Saturday nights.


&&

.DISCUSSION...
Issued at 256 AM CST Wed Nov 4 2026

Surface low pressure was analyzed just southeast of KMSP as of
1 AM CST, with a trailing cold front extending to its south,
just west of the Mississippi River over far eastern IA/MO.
Aloft, GOES water vapor imagery depicted a strong negative-tilt
short wave lifting northeast across MO toward western IL. Strong
forcing ahead of this wave, combined with moisture advection on
enhanced 45-50 kt 850-500 mb south-southwesterly flow,
continues to produce an area of rain from the lower Ohio Valley
northwest across the region. This area of rain will continue to
shift to the north-northeast, with the trailing edge of the more
organized precipitation along the I-39 corridor eventually
moving east of the forecast area this morning. Though drier mid-
level air will spread across the area, lingering low-level
moisture will likely continue to support the potential for some
patchy light rain or drizzle at times through the day. Strong
south winds sporadically gusting 25-30+ mph ahead of the cold
front overnight have held temperatures in the 60s overnight,
though as winds shift southwest and ease a bit with the cold
frontal passage today, temperatures will gradually fall into the
50s. Lingering cloud cover and breezy southwest winds tonight
will keep temperatures in the 45-50 degree range.

The surface low to our north will only slowly drift northeast
across the northern Great Lakes this afternoon into Thursday, as
it occludes and becomes stacked beneath a slow-moving upper
low/trough. This upper trough will be slow to move east over the
next couple of days, as a series of smaller-amplitude short
waves rotate about. This will maintain the potential for periods
of scattered showers across the area at times, most notably
Thursday into Thursday night, as a secondary cold front pushes
southeast across the area. Highs in the 50s are expected again
Thursday, with temperatures dropping into the upper 30s/low 40s
Thursday night in breezy north flow behind the cold front.

Guidance is in decent agreement in digging a short wave
southward into the upper trough over the Great Lakes region
Thursday night, and developing a new closed upper-level low over
lower MI by early Friday. This looks to reinforce low-level
cold advection across the western Great Lakes region, setting up
lake-effect showers over Lake Michigan and northwest IN Friday
into Friday night, before the upper trough axis shifts
east/southeast, and eventually lowers inversion heights over
the lake. Model ensembles then indicate surface high pressure
builds south across the upper Midwest and Mississippi Valley
Friday night into Saturday. Decreasing cloud cover and
diminishing winds associated with the surface ridge, combined
with sub-zero H8 temps may set the stage for freezing conditions
especially across the IL portion of our CWA late Friday
night/early Saturday morning. Confidence is lower in a freeze
over northwest IN, downstream of the warmer lake and potentially
with some lingering lake-effect clouds. Dry weather is then
expected Saturday/Sunday as the surface continues to drift
southeast. Near average temperatures are forecast (highs in the
50s, lows mainly in the 30s). Ensembles suggest upper ridging
develops into the region early next week, with temperatures
potentially trending slightly above average again Monday-
Tuesday.

Ratzer

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1124 PM CST Tue Nov 3 2026

Key aviation forecast messages:

- SHRA to continue overnight with brief MVFR VSBYs at times.

- CIGs trend down through the night to MVFR and then potentially
  near IFR toward RFD by Wednesday AM.

Waves of showers are expected to continue lifting across the
area through the overnight hours with VSBYs briefly dropping
into the low-end MVFR to IFR range within a narrow ribbon of
heavier showers. Ceilings are expected to steadily decrease to
MVFR over the next few hours and remain through the end of the
period, potentially near-IFR toward RFD.

Winds remain at least sporadically gusty out of the south
southeast early this evening and expect gusts into the 20-25 kt
range to continue through the overnight hours. A brief SSW wind
shift may occur with the narrow ribbon of heavier showers as
they move through. Winds then gradually trend more southerly and
then southwesterly overnight into Wednesday morning, remaining
breezy through Wednesday night.

There continues to be a signal for patchy drizzle during the
late afternoon and evening timeframe on Wednesday. If this
persists an introduction of VCSH or a PROB30 for -DZ may become
warranted. Confidence remains too low to include with this
update.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 PM CST Thursday for the IL and IN
     nearshore waters.

&&

$$

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