FXUS63 KLOT 230542
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1242 AM CDT Sun Aug 23 2026

.KEY MESSAGES...

- Dangerous swimming conditions at unprotected beaches in Cook
  County and northwest Indiana today.

&&

.DISCUSSION...
Issued at 231 PM CDT Sat Aug 22 2026

It's a pleasant and quiet Saturday across the area with early 
afternoon temperatures in the upper 70s to around 80 and 
diurnally-driven cumulus starting to fill in overhead. Up 
north, a handful of showers and a couple of thunderstorms have 
recently blossomed along the eastern WI lakeshore with higher 
coverage found farther north near the Door Peninsula and UP of 
Michigan. These developed as a potent vort max and digging 
trough axis swing across the upper Midwest. The cold advection 
aloft has allowed for an ample reservoir of instability to build
around the region while plenty of broad forcing is around to 
drive scattered convection. Coverage will attempt to spread 
south over the next few hours and a few isolated showers/storms 
may attempt to go up over portions of far northeast IL and 
northwest IN before the end of the afternoon. A considerable 
amount of mid level dry air, however, should greatly limit 
overall coverage and make it largely difficult for cores to 
produce lightning. 

This evening, a secondary vort/backdoor cold front will drive 
down the windward side of the trough providing continued 
opportunities for showers and storms to develop over the lake 
during the night. The backed wind field should steer any 
evening/overnight activity into northwest Indiana. An isolated 
shower or two may even linger past daybreak into northern Porter
County. In the forecast, maintained slight chances for rain and
thunderstorms over and around the lake this afternoon which 
then focus into northwest Indiana for the evening and night. In 
addition to the precip potential, the added cooling aloft 
brought on by that secondary vort will further steepen up lapse 
rates over the mild lake waters such that waterspouts may 
develop over the lake this evening through early Sunday morning.

With the trough ejecting to our east tomorrow, surface high 
pressure will slide into the region and bring quiet conditions 
to the early part of next week. Afternoon temperatures are 
forecast in the middle to upper 70s on Sunday and Monday and 
around 80 for Tuesday. A synoptic system is favored to move 
across the upper Midwest during the middle of the week and bring
shower and storm chances to the area in the Tuesday night to 
Thursday window. A lot of uncertainty still revolves around this
system, including if there may be any appreciable severe 
threat, so we'll leave it at that for now and keep an eye on 
model trends over the coming days.

Doom

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1242 AM CDT Sun Aug 23 2026

A small patch of mid-level clouds that produced light showers 
in southeast WI have decreased in coverage over the past hour. 
This will continue to drift southeast over the next few hours 
into northwest Indiana. Still can't rule out a few spotty 
showers into northwest Indiana and have added a VCSH mention at 
GYY.

Otherwise expect dry and VFR conditions through the period with
diurnal cumulus developing around 6000 feet by mid morning. 
Light and variable winds early this morning will increase and 
settle into a prevailing NNW kt after daybreak with the 
occasional gust into the upper teens to around 20 kt in the 
afternoon. Winds then ease and become light and variable again 
after sunset.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement from 4 AM CDT early this morning 
     through this evening for ILZ103-ILZ104.

IN...Beach Hazards Statement from 4 AM CDT early this morning 
     through this evening for INZ001.

     Beach Hazards Statement through this evening for INZ002.

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

     Small Craft Advisory until 10 PM CDT this evening for Gary to 
     Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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