912
FXUS63 KLOT 222325
AFDLOT

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

.KEY MESSAGES...

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

- Fall-like temperatures early/mid next week.

&&

.DISCUSSION...
Issued at 206 PM CDT Fri Aug 22 2025

A strong upper low and an associated surface low over Manitoba
will shift eastward into Ontario tonight into Saturday. While this
low will stay well north-northeast of our area, an associated
cold front shifting southward across the Upper Midwest this
evening will shift across our area during the day on Saturday. A
low potential (~20%) for a period of widely scattered showers (and
maybe a thunderstorm) will exist with this frontal boundary
beginning late tonight (after 2 AM) across far northwestern IL,
then during the early to mid morning hours of Saturday across the
much of northern IL north of I-80. Most areas are likely to remain
dry, and in the areas it does rain amounts will remain light
(under a tenth of an inch). A few additional isolated to widely
scattered showers and thunderstorms will be possible (~20% chance)
with the frontal boundary Saturday afternoon, primarily to to
southeast of I-55.

The Canadian upper low will carve out deep mid-upper level trough
across the Great Lakes Sunday into the first half of next week.
This will favor a period of below average and rather pleasant
temperatures next week as a much cooler Autumn-like airmass shifts
into the area on breezy west-northwesterly winds in the wake of
Saturday`s cold front. High temperatures in this airmass will be
favored to only be in the low to mid 70s Sunday through the middle
of next week. Cool overnight lows are also expected, with
readings likely to drop into the 40s to lower 50s outside of
Chicago! Late in the week, temperatures should begin to slowly
moderate back close to the 80 degree mark.

Outside of some possible lake effect showers early next week
across parts of northwestern IN, an extended period of quiet and
dry weather is expected next week.

KJB

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 625 PM CDT Fri Aug 22 2025

Aviation forecast concerns for the 00Z TAFs:

- Weak lake breeze stalled vicinity ORD/MDW early this evening.

- Brief period of VFR SHRA possible Saturday morning along a
  cold front.

- Breezy WNW winds with gusts 20-25 kt Saturday afternoon.

Combination of local TDWRs and KLOT 88D radar imagery depicts
the weak lake breeze boundary has stalled near/across the far
E/NE portion of KORD and the northeast corner of KMDW as of
early this evening. Boundary does not appear to have any push to
it, and will likely wash out over the next 1-2 hours just east
of these airports. Did see some brief E-SE directions in ORD
ITWS wind sensors on the northeast side of the field little
while ago, but the the overall trend is expected to be light
SSW-WSW winds as we head into the evening/overnight hours.
Winds will eventually turn WNW behind a cold front later
Saturday morning/midday, with sustained speeds increasing into
the 12-15 kt range with gusts increasing into the 20-25 kt range
during the afternoon.

Otherwise, VFR conditions are expected through the period. There
is a chance of some low-impact VFR SHRA for perhaps a 2-3 hour
period ahead of the cold front early Saturday. Added a prob30
mention at KRFD where high-res ensemble guidance probabilities
are highest (though still fairly low). While can`t rule out a
few stray shra/sprinkles, probs decrease farther east toward
the Chicago metro and thus maintained dry TAFs for these
locations.

Ratzer

&&

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

&&

$$

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