FXUS63 KLOT 240548
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1248 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 135 PM CDT Sun Aug 23 2026

The weather pattern across the country for the next week looks to be 
dominated by a western ridge with troughing over the Great Lakes and 
Northeast. This leaves our area in northwest flow with pleasant 
temperatures and generally below average precipitation.

Surface high pressure will settle into the middle Mississippi 
Valley and western Great Lakes tonight through Monday night. 
This will result in light/calm winds, low dewpoints, and 
seasonable temperatures. Once diurnal cumulus dissipates this 
evening, skies should be clear tonight. The clear skies, low 
dewpoints, and calm winds should allow for strong radiational 
cooling. Low temperatures tonight should drop into the 50s, 
coolest away from the urban heat island where some of the 
typically colder spots could even dip into the upper 40s. While 
the boundary layer is dry, the nearly ideal radiational cooling 
set-up could allow for some areas of ground fog late tonight 
into early Monday morning, especially the typically fog favored 
low lying and cold air drainage areas. 

Monday should be a near carbon copy of today, but with less wind. In 
fact, not much change in the weather is expected through Tuesday. 
Later Tuesday into Tuesday night the longwave trough over the Great 
Lakes is expected to scoot off to the east, but fast on its heels 
looks to be another shortwave which will help reestablish the long 
wave trough over the Great Lakes and Northeast. A cold front 
associated with that next shortwave trough is progged to move across 
the area sometime Wednesday or Wednesday night. A frontal boundary 
stalled out across the Gulf States should limit moisture return in 
advance of this cold front. Despite somewhat marginal moisture 
return, fairly strong forcing and cooling temps aloft with the 
approaching upper trough could support some showers/storms when the 
front moves across the region sometime around Wednesday timeframe. 
Frontal timing could also play a role in coverage of showers and 
storms, if the front were to move through at a less diurnally 
favorable time, that would result in lower storm chances and 
rainfall amounts. 

In the wake of the front, another period of sunshine and seasonable 
temperatures with comfortable humidity looks to be on tap Thursday 
into Friday. There are some indications the long wave pattern across 
the CONUS could turn more zonal and potentially lead to more rain 
chances into next weekend, but that is still far out and confidence 
is not terribly high.

- Izzi

&&

.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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