739
FXUS63 KLOT 072000
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
300 PM CDT Tue Oct 7 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 /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1223 PM CDT Tue Oct 7 2025

Key Aviation Messages for the current TAF period:

- MVFR cigs through the early afternoon

Lingering lake effect showers remain over the lake and near
Chicago terminals. There is the potential for some lower vis
down at worst to 3 SM and with some lower MVFR cigs through 20Z
(earlier at ORD) if they pass directly over a terminal. Higher
MVFR cigs are expected to linger through the early afternoon,
but cloud cover will gradually push east and drier, VFR
conditions will return.

Winds will be mostly out of north if not northeast with isolated
gusts into the upper teens. Winds will switch to the northwest
after sunset before returning to the northeast Wednesday
morning. There remains a chance for some MVFR cigs returning on
Wednesday morning, but it was kept out of the TAF for now.

DK

&&

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

     Small Craft Advisory until 10 AM CDT Wednesday for the IN
     nearshore waters.

&&

$$

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