260
FXUS63 KLOT 030743
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
243 AM 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 /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1234 AM CDT Sun Aug 3 2025

- VSBY reductions in smoke/haze a possibility again today.

Winds are currently calm to variable under 5 kt and will remain
so for the remainder of the night through mid morning. Winds
then settle into a prevailing easterly direction through the
rest of the day near and under 10 kt. Winds then ease again
after sunset.

A greater concentration of wildfire smoke is expected to drift
into the area again today and could lead to a period of
visibility reductions as low as 3-5 SM at times. Confidence in
timing and how low the visibility will get remains low but would
not be surprised to see occasional dips to MVFR across parts of
the broader region. For now will continue to account for this
with "6SM HZ" and adjust based on upstream trends. The smoke
could then linger overnight into early Tuesday morning before
lifting back north of the area.

Petr

&&

.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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