782
FXUS63 KLOT 221055
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
555 AM CDT Sat Aug 22 2026

.KEY MESSAGES...

- Isolated to widely scattered shower or storm possible (15-20%
  chance) this afternoon, mainly near Lake Michigan.

- Dangerous swimming conditions expected at Porter County Lake
  Michigan beaches today, then at all Indiana and Cook County
  Lake Michigan beaches late tonight and Sunday.

&&

.DISCUSSION...
Issued at 236 AM CDT Sat Aug 22 2026

A cold front is currently analyzed roughly from a Chicago to
Galesburg line early this morning and is continuing to slowly
drift south and east out of our forecast area. Generally
speaking the better shower and thunderstorm coverage ahead of
the front has been in central IL, but a couple of showers have
been festering in southern Newton, Jasper, and Benton counties.
These showers may briefly produce a rouge lightning strike prior
to exiting these areas over the next hour, but otherwise dry
conditions are expected for the rest of the night.

In the wake of the cold front, winds will become northwesterly
and gradually increase in speed through the morning with gusts
expected to peak around 20-25 mph (locally up to 30 mph) this
afternoon. These northwest winds will build waves on Lake
Michigan today and result in dangerous swimming conditions,
especially into Porter County, IN beaches. As wind directions
become more northerly tonight, the large waves are forecast to
pivot westward into Lake (IN) County and Cook County beaches
overnight tonight and will persist through Sunday evening. As a
result, a Beach Hazard Statement remains in effect for Porter
County, IN starting at 10 AM today and lasting through Sunday
evening with new Beach Hazard Statement issued for Lake (IN) and
Cook Counties starting late tonight through Sunday evening. If
planning to head to the beach today make sure to check the surf
conditions and remember to stay dry when waves are high!

Aside from the breezy north-northwest winds today, mostly dry
conditions are expected as drier air filters into the region.
However, broad upper troughing over the Great Lakes is expected
to linger through much of today and will allow the shortwave
trough in northern WI to pivot overhead this afternoon. While
overall moisture looks to be meager to say the least, forecast
soundings continue to show some modest instability and some low-
level moisture lingering near Lake Michigan which may be
sufficient to kick off isolated to widely scattered showers and
perhaps a thunderstorm this afternoon (15-20% chance). That
said, no severe weather is expected today and any showers/storms
that do develop should wane around or shortly after sunset.
Otherwise, expect mostly to partly cloudy skies with seasonably
cool temperatures in the upper 70s to around 80 degrees.

The upper troughing will gradually shift into the eastern Great
Lakes tonight as high pressure builds into the Midwest. This
will result in completely rain-free conditions for Sunday,
Monday and most likely Tuesday. However, continued northwest
flow will keep temperatures on the cooler side for this time of
year with highs Sunday and Monday in the mid to upper 70s and
overnight lows in the 50s to around 60. Temperatures are
forecast to moderate a bit on Tuesday as winds turn more
southerly, but highs still look to top out in the upper 70s to
lower 80s at best.

While we enjoy a well deserved break in the weather, another
shortwave trough is forecast to be traversing across the Pacific
Northwest and Northern Plains early next week before pivoting
into the Great Lakes towards the middle of the week. Guidance
continues to show that a cold front should develop ahead of this
shortwave and is progged to move through the region sometime
during the Wednesday to Thursday timeframe. While there is
overall good agreement on this evolution amongst ensemble and
deterministic guidance, there is a lot of uncertainty around
when exactly the wave and associated front will arrive in
northern IL and northwest IN thus making this part of the
forecast lower confidence. Bottom line expect to see increasing
shower and thunderstorm chances towards the middle portion of
next week and keep checking back for more specifics as we get
closer in time. Though, temperatures should also be increasing
towards more typical late August readings ahead of this system
too.

Yack

&&

.AVIATION /12Z TAFS THROUGH 18Z SUNDAY/...
Issued at 555 AM CDT Sat Aug 22 2026

Forecast concerns for the terminals...

- Breezy northwest winds today gusting around 20-25 kts.

- Low chance (15-20%) for an isolated shower or storm this
  afternoon.


Generally quiet weather conditions are expected at the terminals
today in the wake of last night`s cold front. Winds will
gradually increase through the morning with gusts peaking around
20-25 kts this afternoon out of the northwest. Though, a lake
breeze at GYY does look to result in a period of northeast winds
after 20z there. While gusts are expected to ease after sunset,
6-8 kt winds will prevail overnight into Sunday before some
15-20 kt gusts return at the tail end of the TAF period. Otherwise,
expect VFR conditions to prevail through the period with SCT to
BKN 5000 ft ceilings near the lake. However, there are some MVFR
ceilings developing over the lake early this morning that may
result in a few hour window of MVFR conditions at GYY and maybe
ORD and MDW through mid-morning.

Lastly, there is a low chance (15-20%) for an isolated shower or
storm to develop near Lake Michigan this afternoon (mainly
between 19z and 00z if they occur) as the shortwave trough over
WI pivots through. Given the drying mid-levels suspect
shower/storm coverage will be very spotty and therefore
confidence on showers/storms actually reaching the Chicago area
terminals is low. So for now have opted to forego a formal TAF
mention, but will keep a close eye on trends.

Yack

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement from late tonight through Sunday
     evening for ILZ103-ILZ104.

IN...Beach Hazards Statement from late tonight through Sunday
     evening for INZ001.

     Beach Hazards Statement from 10 AM CDT this morning through
     Sunday evening for INZ002.

LM...Small Craft Advisory from 4 AM to 7 PM CDT Sunday for Wilmette
     Harbor to Calumet Harbor IL-Calumet Harbor to Gary IN.

     Small Craft Advisory from 10 AM this morning to 10 PM CDT
     Sunday for Gary to Burns Harbor IN-Burns Harbor to
     Michigan City IN.

&&

$$

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