660
FXUS63 KLOT 020530
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1230 AM CDT Sat Aug 2 2025

.KEY MESSAGES...

- Wildfire smoke will continue to cast a milky look to the sky
  for the foreseeable future.

- Pleasant weather characterized by seasonably cool temperatures
  and low humidity levels will prevail through early next week.

&&

.DISCUSSION...
Issued at 140 PM CDT Fri Aug 1 2025

Through Saturday:

A surface high pressure system centered over the Great Lakes
will serve as the primary influence on our weather tonight and
tomorrow. Incoming upper-level cloud cover will limit otherwise
ideal conditions for radiational cooling tonight (light winds,
low humidity levels). Overnight lows will range from the lower
50s in outlying areas to the lower 60s lakeside. Tomorrow looks
similar to today with an east-northeasterly breeze and highs in
the mid to locally upper 70s. Upper-level smoke will continue to
provide a murky look to the sky for the foreseeable future.

Borchardt


Saturday Night through Friday:

High pressure centered across Wisconsin and Lower Michigan on
Sunday will drift eastward to the Canadian maritime provinces
through the middle of next week. The broader mid-level flow
across the CONUS will remain more-or-less blocked with a 600dam
500 hPa ridge over the southwest states and a weaker ridge
crossing southern Canada. Between these ridges and the surface
high to the east, a mid-level trough over the central California
coast will round the southwest ridge into the central CONUS on
Monday before becoming increasingly sheared across our area
Tuesday into Wednesday. Atlantic-based moisture will be drawn
NNW toward the lower Ohio and mid-Mississippi River Valleys by
Monday and especially Tuesday. This would ultimately support
isolated to widely scattered diurnally-driven thunderstorms as
close as central Illinois Monday afternoon and over the entire
forecast area on Tuesday and possibly into Wednesday. A majority
of the forecast area should remain dry during this period,
though will continue to advertise higher chances on Tuesday. A
broad trough crossing the far northern Great Lakes late in the
week will erode a low-amplitude ridge nosing northeastward into
the southern Great Lakes, supporting the potential for an MCS
episode somewhere across the western Great Lakes during this
time.

Kluber

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1230 AM CDT Sat Aug 2 2025

High pressure will keep VFR conditions around the terminals
through the current period. Winds will remain onshore at or
below 10 knots this afternoon. Wildfire smoke remains in the
region for hazier skies and may result in occasional visibility
reductions to MVFR levels.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Air Quality Alert until midnight CDT tonight for ILZ005-ILZ006-
     ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106-
     ILZ107-ILZ108.

IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002-
     INZ010-INZ011.

LM...None.

&&

$$

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