398
FXUS63 KLOT 282002
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
302 PM CDT Thu Aug 28 2025

.KEY MESSAGES...

- Dangerous swimming conditions at all Lake Michigan beaches
  through Friday afternoon.

- Comfortable conditions for outdoor activities are expected
  through the Labor Day holiday weekend, with the warmest
  afternoon temperatures on Sunday and Labor Day (Monday).

- A more substantial cool-down is expected behind a strong cold
  front midweek next week.

&&

.DISCUSSION...
Issued at 302 PM CDT Thu Aug 28 2025

Through Friday:

It appears the various limiting factors for convection this
afternoon are hampering things even more than expected as of
this writing. With already dry mid-levels on observed aircraft
soundings and further dry air advection through the rest of the
afternoon, the window for any showers to take off near the
backdoor cold front pushing inland, let alone any storms, may
have closed. With that said, did keep in slight chance PoPs
until sunset primarily inland of Lake Michigan and east of I-39.

North-northeast winds have come up as expected on the lake, with
waves responding, steadily building to roughly 2-4 feet on the
Illinois side (IN side lagging a bit as expected at 1-3 feet),
likely up to 4 feet plus by around sunset. Brisk northerly
winds will uptick through the evening from increasing low-level
cold air advection over the still warm waters of Lake Michigan.
This will allow waves to build to as large as 5-8 feet.
Hazardous/dangerous to potentially life threatening swimming
conditions will persist through at least Friday morning. The
Beach Hazards Statement is in effect through 4 PM Friday, which
could be a bit on the long side, but not uncommon for waves to
hold on longer than forecast, so no changes planned going
headlines.

Seasonably strong, expansive high pressure around 1025 mb will
build southward from the northern Lakes tonight into Friday.
This will bring an unseasonably cool start to Friday, though not
as cool as a few mornings ago (some spots as low as ~40F).
Friday afternoon will be pleasant and comfortable underneath
fair weather Cu with highs in the lower to mid 70s inland and
upper 60s lakeside.

Friday Night through Thursday:

A mid-level disturbance may yield some shower activity across
portions of the upper MS Valley Friday night into Saturday that
should hit a wall of dry air locally to inhibit anything more
than virga from mid-level overcast. Can`t completely rule out a
few sprinkles across the northwest CWA west of I-39. Otherwise,
the thinking for a pleasant and dry Labor Day Weekend (no heat
and humidity like in previous years) remain unchanged. It will
be cool at night and in the early mornings and 70s in the
afternoon, locally around 80F on Monday. It won`t be an ideal
pool weekend, but great for all other outdoor activities.

Tuesday should be similar to Monday with high pressure still in
control. A large, deep upper trough and strong cold front is
expected to move across the area midweek. This will bring the
next chance of showers and perhaps a few thunderstorms
(strong dynamics compensating for limited moisture) on
Wednesday. A truly mid-October like cool airmass along with
breezy westerly winds is than expected to settle across the
region for the end of next week. Forecast highs are in the
lower-mid 60s next Thursday!

Castro

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1240 PM CDT Thu Aug 28 2025

Key Aviation Messages for the current TAF period:

- Scattered showers possible along and behind a cold front this
  afternoon, where confidence in isolated thunder is low

- Northeast winds through the TAF period

- MVFR cigs possible during the frontal passage

A cold front is moving down Lake Michigan and switching winds
to the north and eventually northeast as it passes. Cloud
bases with the front have been between 1500 and 2000 AGL as it
has moved through Wisconsin. And while they were more solidly
BKN before, increased in mixing has started to scatter them out
more so. Given recent satellite trends are showing more
scattering occurring, the TAFs kept conditions VFR, with a
BKN020 group listed in the PROB30.

This front does have a 30 percent chance for scattered showers
to develop along and behind it. There is lower confidence in
isolated thunder developing, so that was kept out of the TAF.

Skies will scatter out tonight as winds remain out of the
northeast. There is a chance for patchy fog to reduce
visibilities overnight for areas away from the city of Chicago,
mainly near KRFD, but winds are expected to be consistent enough
to help prevent it from impacting terminals. There is a chance
for mid to high clouds to build in around and after 18Z
tomorrow, but it was kept out of the TAF for now.

DK

&&

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

IN...Beach Hazards Statement through Friday afternoon for INZ001-
     INZ002.

LM...Small Craft Advisory until 1 PM CDT Friday for the IL
     nearshore waters.

     Small Craft Advisory until 10 AM CDT Friday for the IN
     nearshore waters.

&&

$$

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