628
FXUS63 KLOT 201802
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1202 PM CST Thu Nov 20 2025

.KEY MESSAGES...

- Patchy drizzle and fog will linger through the early morning
  hours today, with cloud cover hanging on through tonight.

- Some light rain is possible Friday, especially south of I-80.

&&

.DISCUSSION...
Issued at 305 AM CST Thu Nov 20 2025

Thick stratus deck currently blankets the region with recent
ACARs sounding from MDW and KLOT VWP both pointing toward 5-6kft
thick stratus deck. Some modest shear within the cloud bearing
layer is resulting in some areas of light drizzle. CIGs have
been slowly building down overnight with some patchy fog. No
reason to think that patchy drizzle and fog won`t linger past
sunrise. By later this morning, Bufkit soundings show the depth
of the stratus decreasing, which could lead to a lessening of
the drizzle threat.

Stratus deck should result in temps only inching up 2-4F degrees
this afternoon and have continued the trend of the previous few
forecasts of lowering high temps for today. Interestingly, NAM
and RAP forecast soundings in particular, show stratus depth
increasing again later this afternoon into this evening in
response to glancing blow of ascent from a shortwave passing to
our north. It is plausible this could lead to another round of
patchy drizzle very late this afternoon into this evening,
especially northern CWA. Shallow depth to moisture should keep
chances of measurable precipitation low, but another bout of
some drizzle certainly seems plausible.

Vigorous upper low seen on water vapor imagery over southern AZ
early this morning is progged to move northeast to the central
high Plains by early Friday morning, then quickly shear out as
it races eastward toward the mid-Mississippi Valley Friday into
Friday night. Rain associated with this system will likely light
up over Missouri and downstate IL tonight, likely remaining
south of our CWA. By Friday, some of this rain could lift north
into mainly southern portions of the CWA. Dry air advection in
the wake of the weak cold front will likely hinder the northward
progression of the rain shield Friday, keeping the best rain
chances south of I-80. The drier air should scour out the
stratus north of I-80, but extensive mid-high level cloudiness
will probably keep our chances at seeing the sun limited.

Dry weather is expected over the weekend into at least Monday
with moderating temperatures. By Sunday and Monday, highs should
get well into the 50s with a few 60 degree readings possible if
high cloudiness isn`t too extensive in advance of the next
system. Medium range guidance continues to advertise a big
trough moving across the country Tuesday through Thanksgiving
next week. Big troughs like this often move out slower than
progged this far out, so confidence in timing is low, especially
given we`re looking a split flow pattern with the potential for
some phasing. Given the complexities of next week`s pattern, saw
no reason to deviate from NBM which advertises increasing precip
chances and eventually colder temps behind the trough.

- Izzi

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1200 PM CST Thu Nov 20 2025

- Periods of LIFR/IFR VSBYs CIGs and patchy -DZ BR possible at
  times through tonight.

Other than some minor visibility and ceiling improvements
little has changed across the area through midday with
continued LIFR to IFR CIGs under an expansive stratus deck and
IFR to MVFR VSBYs due to lingering light mist/BR (lowest outside
of Chicago). While guidance continues to suggest that there
could be further improvement through the afternoon, this could
be counteracted by potential redevelopment of drizzle (20%
chance). Thus, opted to not make big changes to the inherited
TAFs for now and continue to monitor trends. Additional periods
of -DZ may need to be added.

A weak cold front will push across the area late this evening
and overnight with ongoing light south to southwest winds
veering to the northwest in its wake. This feature could be
paired with another round of drizzle and associated VSBY/CIG
reductions (30% chance) from roughly 2-10Z, earliest northwest
and latest southeast.

CIG and VSBY trends are expected to improve through the morning
on Friday, returning back to VFR by the afternoon as the
stratus layer thins and erodes. Another system will graze parts
of the area on Friday, though any associated showers are
expected to remain south of the terminals toward central
Illinois.

Petr

&&

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

&&

$$

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