584
FXUS63 KLOT 011724
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1224 PM CDT Fri Aug 1 2025

.KEY MESSAGES...

- Wildfire smoke will remain in the area through the weekend.

- High swim risks at all Lake Michigan beaches through at least
  today.

&&

.DISCUSSION...
Issued at 300 AM CDT Fri Aug 1 2025

A subtle inverted surface trough, based on recent mesoanalysis,
is moving westward over Lake Michigan and into northeastern
Illinois. Increasing convergence along the shoreline and some
instability has allowed a ribbon of stratocumulus to develop (as
seen on satellite nighttime microphysics) from Kenosha, WI down
to O`Hare. The amount of moisture available remains marginal
but even with weak forcing and instability, it is possible that
some light sprinkles or a shower may to develop this morning
before daybreak. The slight chance for sprinkles and/or showers
will diminish by midday as drier air mixes in.

A broad upper level trough over eastern Canada remains visible
on GOES-19 water vapor imagery as upper level ridge sits over
the western part of the CONUS, with its ridge axis along the
Rocky Mountains. Recent mesoanalysis plots a surface high
sitting along the border of Wisconsin and Minnesota projected to
slink eastward and broaden across the western Great Lakes
through today and tonight. With a drier air mass in place, dew
points should remain in the 50s (maybe just touch 60) with high
temperatures today in the mid 70s. The only downside to this
pattern is the wildfire smoke that is wrapping around the
eastern side of the surface high. Visibilities have improved
compared to Thursday, but there are still plenty of observations
that are reporting between 4 to 7 miles of reduced
visibilities. Luckily, recent models are suggesting that the
thickest plume near the surface will continue to move west of
the city. However, considering that east-to-northeast winds are
expected to remain through the weekend and the amount of smoke
upstream observed on visible satellite last evening, it would
not be surprising if a murky look to the skies remained through
the weekend. Satellite trends will need to be monitored but for
now hazy skies have been kept in the forecast.

Other than the potential for lingering smoke, the high pressure
remaining over the region through the weekend should provide
dry and pleasant conditions. Temperatures will warm gradually
into the 80s with overnight lows in the 50s.

Unfortunately, the surface high begins to move east toward the
Atlantic early next week. As it does, southeast winds will
allow moisture from the Atlantic and the Gulf Coast to be pulled
into the area increasing dew points into the 60s. At the same
time, an upper level trough is projected to eject out of the
Rockies and over the Great Plains. Recent models have slowed
the progression of this trough, suggesting that it may not
approach the area until later on Tuesday. While the timing can
be refined closer to the date as models get a better handle on
it, this pattern certainly supports the return of isolated to
widely scattered showers and storms around mid week next week.
Minor ridging may provide a brief break toward the end of the
week, but then another wave may bring chances for rain at the
end of next week.

DK

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1224 PM CDT Fri Aug 1 2025

There are no aviation concerns through the TAF period.
Northeasterly winds will prevail this afternoon before becoming
light and variable overnight. After daybreak tomorrow, winds
will become east northeasterly once again. Occasional bouts of
largely VFR clouds will prevail. Haze due to wildfire smoke
should continue to increase through the afternoon, though
trapped smoke aloft will maintain a milky look to the sky.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Air Quality Alert until midnight CDT tonight for ILZ003-ILZ004-
     ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
     ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-
     ILZ105-ILZ106-ILZ107-ILZ108.

     Beach Hazards Statement until 4 PM CDT this afternoon for
     ILZ103-ILZ104.

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

     Beach Hazards Statement until 4 PM CDT this afternoon for
     INZ001-INZ002.

LM...None.

&&

$$

Visit us at weather.gov/chicago