612
FXUS63 KLOT 211152
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
552 AM CST Fri Nov 21 2025

.KEY MESSAGES...

- Patches of fog and low clouds will persist early this
  morning.

- A period of rain is possible this afternoon and evening,
  primarily in areas south of the Illinois and Kankakee rivers.

- Following a period of warmer weather over the weekend,
  widespread rain is likely (70%+ chance) late Monday into
  Tuesday.

- Turning much colder for Thanksgiving.

&&

.DISCUSSION...
Issued at 225 AM CST Fri Nov 21 2025

Some early morning fog continues in advance of a weak cold
frontal boundary shifting into the area. However, much of the
dense fog (visibilities <1/4 mile) has been confined south of
the area in central and southern IL and IN. If these trends
continue, we will likely be able to drop the dense fog advisory
across our southern tier counties prior to daybreak. Otherwise,
in the wake of the cold front, a drier low-level airmass will
advect southward into northern IL this morning, bringing an end
to the fog and the persistent area of low stratus. However, in
spite of this, higher level cloud cover will quickly be on the
increase ahead of the next approaching impulse, so another
cloudy day is anticipated today, with highs in the upper 40s to
around 50.

A sheared mid-level impulse and associated weak surface low
will shift eastward across the mid Mississippi Valley through the
day. While this will continue to favor an expansive area of
rainfall into tonight across parts of the Midwest, there will be a
sharp northward gradient in the rainfall setting up across central
IL and IN. Accordingly, the prospects of any meaningful rain
today into tonight continues to diminish across far northern IL,
particularly areas along and north of I-80. We thus continue to
confine chance POPs mainly south of the Illinois and Kankakee
Rivers later today into this evening.

A period of dry weather, with more sunshine and moderating
temperatures is expected for the weekend, owing to an area of
surface high pressure shifting across the mid section of the
country. However, another upper-level low is expected to eject
northeastward out of the Desert Southwest later this weekend. This
system will result in our next good threat of widespread rain as
it shifts across our region in the Monday afternoon through
Tuesday morning time frame. Thereafter, a northern stream impulse
is likely to carve out an upper trough over the Great Lakes into
the Thanksgiving holiday weekend. For our area this will result
in notably colder conditions by Thanksgiving day, with highs
only in the 30s.

KJB

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 552 AM CST Fri Nov 21 2025

Main Item of Note:

- North-northeasterly wind shift at MDW and ORD this afternoon.

There are no significant flying concerns through Saturday
morning. Though the TAF sites except GYY scattered to VFR CIGs
early this morning, can`t rule out temporary MVFR CIGs at times
this morning. GYY should scatter by midday. MVFR VSBY in BR at
RFD, DPA, and GYY should improve by ~14-15z.

At ORD and MDW, light north-northwesterly winds this morning
are expected to shift to north-northeasterly (020-050) this
afternoon, with some uncertainty in timing. An earlier wind
shift is currently favored at MDW vs. ORD, as depicted in the
TAFs. While speeds should remain relatively light, can`t
completely rule out brief near 10 kt speeds observed at runway
sensors. Winds should then return to north-northwest this
evening through Saturday morning. Some minor VSBY reductions in
BR may occur at RFD, DPA, and GYY tonight, though not explicitly
indicated in the TAFs.

Castro

&&

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

&&

$$

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