097
FXUS63 KLOT 240712
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
212 AM CDT Mon Aug 24 2026

.KEY MESSAGES...

- The next chance of showers and thunderstorms is with a cold
  front moving across the area midweek.

&&

.DISCUSSION...
Issued at 212 AM CDT Mon Aug 24 2026

High pressure continues to settle into the mid-Mississippi
Valley and will remain in place through Tuesday. As a result,
dry conditions with generally comfortable humidity are expected
to start off the work week. Temperatures today will once again
be on the seasonably cool side with highs only topping out in
the upper 70s to around 80 this afternoon. A lake breeze is
expected to develop and move inland this afternoon and evening
which will result in cooling temperatures along the lakeshore,
though with lake temperatures in the lower 70s the temperature
drop shouldn`t be overly impressive. Overnight lows tonight
won`t be as chilly as they will be this morning, but will dip
into the mid-50s inland with upper 50s near the lake. As winds
turn more south-southwesterly on Tuesday, warmer air should
begin to advect into the area and result with more seasonable
highs in the lower 80s.

Rain chances are still forecast to increase as we head into the
middle of the week as the shortwave trough over the Mountain
West pivots into the Great Lakes. A cold front is expected to
accompany the shortwave as it moves through the region which
should serve as the impetus for showers and thunderstorms.
Similar to last night, guidance continues to show some
showers/storms developing along the front in the Upper Midwest
on Tuesday and drifting towards northern IL Tuesday night.
Though, with moisture return continuing to look more limited
locally and the unfavorable diurnal time, these showers/storms
should be in a decaying state as they approach IL (if they make
it at) so the greatest coverage of any rain Tuesday night should
be near the IL-WI line. The front is expected to continue
moving across northern IL and northwest IN on Wednesday which
should allow for the redevelopment of showers and thunderstorms
Wednesday afternoon and evening as diurnal destabilization
occurs. Despite the decent MLCAPE values noted in forecast
soundings, shower and storm coverage continues to look spotty
likely due to weaker frontal convergence and the core of the
shortwave currently forecast to be centered over MI. So while
this may mean some areas get little rain, our official forecast
will continue to advertise broad 30 to locally 50% chances for
showers and storms on Wednesday. Regardless of storm coverage,
deep layer shear values of 25-35 kts are still expected in the
area which may support a few storms becoming strong to locally
severe Wednesday afternoon and evening. With confidence on storm
coverage being low, our area has not been added to any severe
outlooks at this time, but we will continue to keep an eye on
this potential.

The cold front should exit the area late Wednesday night into
Thursday morning which looks to allow another surface high to
build into the area. However, with some subtle frontal timing
differences noted in ensemble guidance the exact time the front
exits remains uncertain. Nevertheless, the building high
pressure behind the front will result in a period of dry weather
to close out the work week with otherwise seasonable
temperatures expected. The signal remains for a shift towards a
more active upper-level pattern as we head towards the beginning
of next week which looks to mean more shower and thunderstorm
chances so enjoy the nice weather while we have it.

Yack

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1248 AM CDT Mon Aug 24 2026

Key aviation forecast messages:

- Lake breeze may turn winds east this afternoon at ORD/MDW

Winds will remain light and variable through daybreak,
potentially leaning more consistently westerly at the Chicago
terminals due to a weak land breeze. Winds then settle into a
prevailing NW to NNW after daybreak around 5-10 kt. A lake
breeze is forecast to drift inland during the afternoon. While
confidence in the timing that it reaches ORD/MDW remains on the
lower side, did move up the wind shift by an hour at MDW to 20Z
based on hi-res guidance trending a bit earlier there
(maintained 22Z at ORD for now).

VFR conditions are forecast through the period with varying
coverage of diurnal cumulus around 5000 ft and occasional
higher clouds. Can`t fully rule out shallow fog (MIFG)
developing outside of Chicago early this morning but the
potential is too low to include a formal TAF mention.

Petr

&&

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

&&

$$

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