500
FXUS63 KLOT 080525
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1225 AM CDT Wed Oct 8 2025

.KEY MESSAGES...

- Mostly dry weather and cooler (more seasonable) temperatures
  are expected through the remainder of the work week.

- A gradual warming trend commences heading into the weekend
  with a return of highs in the 70s.

&&

.DISCUSSION...
Issued at 300 PM CDT Tue Oct 7 2025

A much cooler airmass has moved into the region in the wake of
a cold front with temperatures back to more seasonable levels
(to even slightly cooler than normal). The steady rain has since
ended but a few patchy areas of light drizzle/sprinkles may
linger south of I-80 and near the lakeshore for the next couple
of hours. This should all gradually come to an end by this
evening with skies clearing overnight. This should allow
temperatures to cool readily after sunset with forecast lows in
the 40s to lower 50s (warmest in Chicago). Some upper 30s can`t
be ruled out in our typical cool rural spots in interior
northern Illinois (mainly west of the Fox River Valley). Think
that winds will remain just strong enough to limit frost
development this far southeast.

Similar to today`s light lake effect showers/drizzle there is a
signal for at least lake effect cloudiness during the day on
Tuesday, especially into northeast Illinois. Forecast vertical
profiles suggest that this cloud layer will be rather shallow
which should limit coverage and have opted to hold off on a
formal gridded forecast mention with this update.

Surface high pressure remains in place across the Upper Midwest
through midweek with cool north to northeasterly winds holding
temperatures in the 60s across the area. Overnight lows both
Wednesday and Thursday night could dip into the upper 30s
outside of the Chicago metro which may lead to patchy frost
development toward daybreak.

An upper level shortwave is progged to dive southeast across
Ontario and Michigan on Friday. Current blended guidance keeps
the area dry during this time with the majority of the
precipitation remaining tied to the better forcing northeast of
the local area although a few spotty showers can`t be fully
ruled out near an associated weak surface cold front.

A gradual warming trend commences heading into the weekend as
mid-level ridging builds into the region in the wake of the
Friday shortwave with a return to high temperatures in the 70s.
Blended shower chances (20-30%) early next week seem reasonable
at this distance though there remains plenty of uncertainty
with respect to the track of these features (which could end up
west of the area leading to continued dry conditions).

Petr

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1225 AM CDT Wed Oct 8 2025

Main Items of Note:

- Timing of wind shifts to north and then northeast at ORD and
  MDW this morning.

- Low chance for a period of MVFR CIGs this morning.

Another overall quiet 24-30 hours is in store. A secondary cold
front passage will shift winds to northerly prior to sunrise,
with some uncertainty on timing. Lake influence will cause winds
to go over to northeast sometime in the mid to late morning,
persisting into or through the evening. Lake effect clouds,
primarily VFR, should develop as well, though can`t completely
rule out a short window of 2000-2500 ft MVFR CIGs near the lake.

Castro

&&

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

&&

$$

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