483
FXUS63 KLOT 150530
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1230 AM CDT Wed Oct 15 2025

.KEY MESSAGES...

- Some scattered showers expected late tonight into Wed morning,
  mainly north of I-80.

- A period of showers and possible thunderstorms is expected
  late Friday night or Saturday.

&&

.DISCUSSION...
Issued at 214 PM CDT Tue Oct 14 2025

Weak shortwave trough over Nebraska this afternoon will track
eastward across the Cornbelt and western Great Lakes tonight
into Wednesday morning. Forcing is not progged to be
particularly impressive, but mid-upper level height falls in
conjunction with some modest isentropic ascent on the 295-300K
surfaces should be enough to support some scattered showers
later tonight into Wednesday morning. Greatest coverage should
be north of I-80 and especially closer to the IL/WI border. Low
level moisture/cloudiness could get trapped beneath a sharpening
frontal inversion Wednesday, so much of the day could end up
socked in cloud cover. The cloud cover should help keep temps
noticeably cooler than today, though there could be a sharp
temperature gradient near or over our southern/southwestern CWA
where skies could clear out earlier.

While there are some differences in smaller scale details with
time, guidance is largely in agreement on a transition to a more
active, progressive and fairly amplified longwave pattern over
North America late this week through at least the first half of
next week. This should result in more frequent rain chances
along with some typical autumnal temperature swings.

As upper low and longwave trough over the West Coast today moves
eastward, look first for upper ridging to build east into the
area later this week with a warming trend Thursday and
especially into Friday. As the trough and accompanying cold
front move across the area later Friday night or Saturday, it
should be accompanied by showers and possibly a few
thunderstorms. A much cooler (though fairly seasonable) air
mass will filter into the area in the wake of the front Saturday
night through Monday.

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1230 AM CDT Wed Oct 15 2025

Forecast concerns include...

Scattered showers through late morning.
Gusty northeast winds early this morning.
Possible mvfr cigs mid morning to mid afternoon.

Scattered, mainly vfr showers are expected through the overnight
hours. Eventually, toward daybreak, the shower coverage may
increase with brief mvfr visibilities possible. These showers
will slowly dissipate through the mid/late morning with vicinity
mention still looking reasonable through midday. Cigs are
expected to remain generally vfr through daybreak and then there
is some guidance showing the potential for mvfr cigs later this
morning into early this afternoon, especially across far
northern IL. Confidence is low for prevailing mvfr cigs and have
maintained scattered mention for now. Low vfr cigs will likely
continue into this evening and then are expected to scatter out
into early Thursday morning.

Northeast winds will continue through this evening with gusts
into the 15-20kt range through daybreak this morning. Winds will
turn more easterly tonight into early Thursday morning with
speeds becoming light. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 1 PM CDT this afternoon for the IL
     nearshore waters.

     Small Craft Advisory until 7 AM CDT this morning for the IN
     nearshore waters.

&&

$$

Visit us at weather.gov/chicago