210
FXUS63 KLOT 230528
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1228 AM CDT Wed Sep 23 2026

.KEY MESSAGES...

- Widely scattered showers may persist overnight.

- Generally slightly below to below average temperatures
  expected into at least the first part of the upcoming
  weekend.

&&

.DISCUSSION...
Issued at 210 PM CDT Tue Sep 22 2026

Water vapor imagery early this afternoon shows a compact, but
well defined closed mid-upper level low over eastern IA and
northwest IL. This system has been a bit slower to weaken and
devolve into an open wave than guidance progged yesterday. The
18z sounding that just came in from DVN depicts a deeply
nearly saturated to saturated column with a PWAT of 1.31", which
is notably more moisture than depicted in most guidance
yesterday. The likely stronger forcing with the more defined
mid-upper low combined with greater moisture has resulted in a
greater coverage of showers and even a couple of isolated
thunderstorms this afternoon into the western half our CWA.

Tricky forecast for the next 12-18 hours with guidance
continuing to largely keep rain chances minimal and quickly
weakening and opening up this system. Certainly not seeing any
evidence in water vapor imagery of imminent weakening, and
guidance`s the poor handling of this feature over the past 24
hours there is reason to be skeptical that the showers out there
will imminently dry up. Recent ACARs soundings from MDW do
depict a pretty stout dry layer between 900 and 700 mb, so it is
plausible there will be a decrease in showers as it moves east.
Given the pocket of moisture evident in low and mid level water
vapor imagery with the core of the upper low, think it is
prudent to maintain respectable shower chances into tonight
near the core of this upper low as it moves across the area.

Once this upper low pushes east of the area tomorrow morning, an
extended period of dry weather is expected for the remainder of
the week and likely through the upcoming weekend. A very blocky
upper level pattern is progged to set up across central and
eastern North America, so very little day to day change in our
weather is expected. By later in the weekend into early next
week, some breakdown in the blocking pattern is possible with
upper ridging developing eastward. Assuming this plays out as
progged (lower than avg confidence given the tendency for
guidance to break down blocking patterns too quickly), then a
warning trend would take place late in the weekend into early
next week.

- Izzi

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1228 AM CDT Wed Sep 23 2026

The only forecast concern this period are mvfr cigs after
daybreak through sunset. A 4kft cloud deck has spread across
the area and is expected to lower into mvfr after daybreak for
much of the area with prevailing mvfr cigs expected through
mid/late afternoon. Cigs are then expected to slowly lift back
into low vfr this evening.

There may be an isolated shower or some sprinkles today but
there currently are no favored time periods and chances for
precipitation today are low and no mention is needed at this
time.

East/northeast winds will continue through the period with
speeds increasing after sunrise with gusts into the 15-20kt
range mainly during the daylight hours. Gusts will end after
sunset with speeds diminishing under 10kt this evening. cms

&&

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

IN...Beach Hazards Statement until 10 AM CDT this morning for
     INZ001-INZ002.

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

     Small Craft Advisory until 10 AM CDT this morning for Calumet
     Harbor IL to Burns Harbor IN.

&&

$$

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