140
FXUS63 KLOT 232326
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
626 PM CDT Sun Aug 23 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 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
not terribly high.

- Izzi

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 626 PM CDT Sun Aug 23 2026

Key Aviation Messages for the current TAF period:

- A lake breeze tomorrow afternoon is expected to switch winds
  to the northeast at the Chicago terminals.

Winds are presently out of the northwest with occasional gusts
to 20 knots. A lake breeze did develop east of the Chicago
terminals, but fell apart and so was removed from the MDW TAF.
Winds will gradually diminish and become light after 00Z. There
is a low chance for localized MIFG and BCFG at rural terminals
overnight, but confidence is low.

No significant weather is expected through the TAF period. VFR
conditions are expected and northwest winds are expected to
turn to the east behind a lake breeze tomorrow afternoon.
There is moderate confidence in the timing, but will be re-fined
in later TAF packages.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Beach Hazards Statement until 10 PM CDT this evening for
     INZ002.

LM...None.

&&

$$

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