210
FXUS63 KLOT 031704
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1204 PM CDT Sun Aug 3 2025

.KEY MESSAGES...

- Hazy skies and patchy smoke from wildfires lingers today.

- A gradual increase in temperatures and humidity expected
  through the week.

&&

.DISCUSSION...
Issued at 243 AM CDT Sun Aug 3 2025

Recent mesoanalysis still shows an expansive area of higher
surface pressure over the Great Lakes. It has made for pretty
nice conditions through this past weekend and that trend should
continue today and Monday. Winds will be out of the east around
5 to 10 mph with clearer skies allowing temperatures to reach
the low 80s inland and mid to upper 70s along the immediate
lakeshore. The only negative is the lingering hazy skies from
wildfire smoke. Recent smoke models continue to depict a
slightly higher concentration of smoke to move over the area
today. While there is uncertainty with how much smoke will make
it down to the surface, the forecast kept the mention of hazy
skies and added the mention of patchy smoke. There is still some
uncertainty with how much haze/smoke lingers, but it is not out
of the question that will need to be extended into Monday.

Overnight into Monday, the surface high will start to weaken
and drift eastward toward upstate New York and Quebec. With an
upper level ridge over the Rockies slowly inching east, mid
level flow will turn to the southeast. This will help allow
moisture to be drawn up from the Gulf and the Atlantic and
increase dew points in the region. There is still some
uncertainty with how much moisture makes it northward on Monday
specifically, but with high res models suggesting a weak
inverted surface trough in Central Illinois and slightly higher
moisture, it would not be surprising if some isolated showers
and storms cropped up in the southwestern portions of the
forecast area Monday afternoon. The better chances are certainly
to the south of the area, but PoPs were bumped up slightly.

Moisture will continue to increase on Tuesday. As that trough
continues to move northward, instability and lapse rates should
be better for some diurnally driven showers and storms in the
afternoon. For now, the favored coverage areas would be near and
south of I-80, but could extend farther north as a lake breeze
develops in the afternoon.

DK

The mid and upper level pattern looks to remain fairly blocky
and thus benign the rest of next week. General mid-level height
rises back to or above 590 DaM at 500 mb and warming 850 and
925 mb temps points towards surface temps returning to solidly
above normal Wednesday and beyond, with at least localized 90F
highs Thursday-Saturday aside from any modest Lake Michigan
shoreline cooling. If the blockier pattern holds like some
ensemble guidance suggests, primarily dry conditions will
prevail, though cannot completely rule out isolated diurnal
convection on some of the days. If the pattern breaks down
quicker, which seems like a less likely outcome at this point,
then that would open the door to higher convective chances next
weekend.

Castro

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1202 PM CDT Sun Aug 3 2025

- Visibility reduction in lingering wildfire smoke and fog patches

High pressure over the southern Great Lakes will begin a slow
retreat eastward into Monday. This will maintain generally
lighter easterly wind (some variation between NE and SE) through
the TAF cycle. Some minor visibility reductions in haze/smoke
(4SM-6SM) will continue through this evening with the light
winds in place. It looks like tomorrow as we get more of a SE
wind that the near surface smoke/haze should ease through the
day. There could also be some patchy fog late tonight.

A slow moving disturbance will spread some higher clouds in from the
south and west later Monday, but any shower activity will
remain well south of the terminals.

KMD

&&

.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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