262
FXUS63 KLOT 221106
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
606 AM CDT Fri Aug 22 2025

.KEY MESSAGES...

- Areas of fog (dense in spots) this morning.

- Slight chance (20%) for a few thunderstorms Saturday
  afternoon.

- Fall-like temperatures early/mid next week.

&&

.DISCUSSION...
Issued at 215 AM CDT Fri Aug 22 2025

Main concern in the short term is fog potential early this
morning. Fog thus far has been developing across north central
IN and portions of southwest WI but satellite is starting to
show fog developing across east central IL. Will need to monitor
trends for a possible dense fog advisory with the most favored
areas being along and south of I-80, though dense fog will also
be possible across northwest IL. This fog will lift/dissipate
through mid morning.

High temps today are expected to reach the upper 70s to lower
80s for most areas with a lake breeze expected this afternoon,
though there remains some uncertainty for how far inland the
lake breeze may move.

A cold front will move across the area Saturday with a low
chance of showers toward daybreak Saturday morning across the
northwest cwa with most models staying dry. Additional showers
are possible Saturday morning with perhaps a low chance (20%)
for a few thunderstorms Saturday afternoon, mainly south of
I-80. While confidence is fairly low, maintained going slight
chance pops during this time period along with thunder mention
for Saturday afternoon.

Cooler air will begin to arrive Saturday night and will continue
through the middle of the week with high temps generally in the
70s and low temps in the upper 40s/lower 50s. Usual cool spots
may see mid 40s on a few mornings.

Dry weather is expected for much of next week with the
exception of some lake effect rain showers possible across
northwest IN Sunday night into Monday and again Monday night
into Tuesday. cms

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/... Issued at 600 AM
CDT Fri Aug 22 2025

Aviation forecast concerns for the 12Z TAFs:

- IFR/LIFR fog patches and MVFR ceilings lifting after 14z

- Low-medium confidence in timing of lake breeze/wind shift at
  ORD/MDW this afternoon, though speeds should remain under 9 kt
  for any length of time regardless of direction.

In spite of light low level winds, area wind profilers suggest
enough flow to prevent widespread dense fog. Still,visibilities
in patchy fog have been inching downward overnight outside of
the metro area, and these will most likely to remain down the
longest south of the terminals. There are also some patchy
lower (mostly MVFR/low VFR) clouds about that will lift today
into more of a VFR stratocumulus with time as well.

Model guidance has quite varied solutions for winds,
particularly for ORD/MDW in vicinity of the lake. As the low level
ridge axis moves east, low level flow will shift to westerly,
but it will not be very strong. Therefore conceptually light
winds would be somewhat variable and would also suggest at
least a turn to a SE wind at some point later today at least at
KMDW. Any lake breeze push would not likely be a very strong
(winds under 8-9 kt).

A prefrontal trough will move through NE IL mainly overnight.  The
signal for anything more than a few sprinkles is low. A
cold front will approach the terminals toward the tail end of the 30
hr TAF cycle. All indications are that this will be dry for the
terminals, though it could bring a few showers or even isolated
TS (20%).

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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