902
FXUS63 KLOT 220642
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
142 AM CDT Wed Jul 22 2026

.KEY MESSAGES...

- The next few days will be offer seasonably cool temperatures,
  comfortable humidity values, and no threat of rain.

- Conditions will remain hazardous at all Southern Lake Michigan
  beaches through Thursday morning.

- Heat, humidity, and chances for storms will return early next
  week.

&&

.DISCUSSION...
Issued at 142 AM CDT Wed Jul 22 2026

It sure looks and feels more like fall than the middle of July
early this morning with deep upper-level cyclonic flow anchored
by seasonably cool temperatures and pockets of lake-induced
stratocumulus clouds! The change in regime is exemplified by a
drop in 800mb temperatures of about 12C/24 hours per the last
two 00Z RAOBs at GRB, a range from roughly the 90th to 10th
percentiles. The stage is thus set for a beautiful stretch of
days with seasonably cool temperatures, low humidity values, and
no threat for rain. Highs today will top off in the low to mid
70s and increase by a few degrees each day through the end of
the week. Overnight lows will be comfortable and start in the
lower 50s tonight rising to the lower 60s by Friday night. The
only fly in the ointment in an otherwise pleasant period is
hazardous waves along all southern Lake Michigan beaches today
through Thursday morning.

The reprieve from the heat will be short-lived as upper-level
ridging redevelops across the central United States this
weekend. Highs will climb back into the upper 80s to lower 90s
as early as Sunday and continue through next week. Humidity
levels are also poised to rise with agricultural
evapotranspiration likely augmenting near-surface dew points
into the mid 70s. The next opportunity for storms will arrive in
the Sunday/Monday (July 26/27) timeframe along the precarious
northeastern side of the building upper-level ridge. The EPS in
particular is bullish with 51-member mean MUCAPE already
exceeding 2000 J/kg and over 50% of members with a PWAT
exceeding 2 inches. This will be a period to watch for severe
weather in the general Upper Mississippi River Valley/Great
Lakes region.

Borchardt

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1229 AM CDT Wed Jul 22 2026

Key messages for the 06Z TAF period:

* Breezy northerly winds gradually easing into Wednesday

* Intermittent periods of MVFR cigs through the middle of the
  night

* At GYY, a light shower or sprinkle possible through the middle
  of the night

A broken MVFR deck continues to bleed inland off of the lake
and move over the Chicagoland sites. It`s expected to break up
through the first half of the overnight. VFR is favored to
return after 08Z, if not sooner. Given that sites may bounce in
and out of MVFR, decided to treat this with a TEMPO for MVFR for
the first couple of hours of the period. MVFR may linger later
into the night over GYY where a light shower or sprinkle can`t
be ruled out.

NE winds occasionally gusting to around 20 kt will gradually
ease some through the night as they back to NNW after 09Z.
They`ll flop over to NNE again near end of the morning. Winds
will go light and variable for the evening and night before a
westerly direction takes hold by early Thursday.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement through this evening for ILZ006-ILZ103-
     ILZ104.

IN...Beach Hazards Statement through Thursday morning for INZ001-
     INZ002.

LM...Small Craft Advisory until 10 PM CDT this evening for the IL
     nearshore waters.

     Small Craft Advisory until 4 AM CDT Thursday for the IN
     nearshore waters.

&&

$$

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