NWS Chicago Decision Support Briefing - Forecast

489
FXUS63 KLOT 241109
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
609 AM CDT Fri Apr 24 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms through this afternoon
ahead of a cold front.

- Seasonable and dry conditions over the weekend.

- Scattered severe thunderstorms Monday along with heavy rain
and possible localized flooding.

&&

.DISCUSSION...
Issued at 111 AM CDT Fri Apr 24 2026

While storms continue to slowly dissipate across far west and
northwest IL early this morning, a strong outflow boundary will
need to be monitored as it continues into the western cwa early
this morning. The expectation is for the winds with this
boundary to slowly weaken. Scattered showers and isolated
thunderstorms will be possible through daybreak with a gradual
weakening trend expected. There may be a lull in precipitation
during the mid morning hours and then additional showers and at
least a few thunderstorms are expected to develop along/ahead of
the main cold front. Quite a bit of uncertainty for coverage
with this activity but likely pops seem reasonable from this
distance. This activity will quickly shift east of the area by
mid/late afternoon. The best chance for any stronger storms or
possibly isolated severe thunderstorms appear to be east of the
local area this afternoon.

Winds will shift northerly tonight and remain northeasterly
Saturday and easterly on Sunday as cooler air spreads back
across the area. Low temps both Saturday and Sunday morning are
expected to be in the 40s. Highs inland will be well in the 60s
and likely lower 70s Saturday, low/mid 70s Sunday, but much
cooler temps are expected closer to Lake Michigan.

The models are in general agreement for low pressure to develop
over the southwest Plains Sunday which will then move northeast
across the western Great Lakes Monday night as a cold front
moves across the local area Monday night. Current trends suggest
at least a broken line of strong/severe thunderstorms developing
west of the local area and then quickly moving east of the area
by mid/late Monday evening. With precipitable water values
approaching 1.5 inches by late Monday afternoon, heavy rain may
lead to localized flooding. cms

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 608 AM CDT Fri Apr 24 2026

The residual cold pool of a long-decayed overnight convective
system will continue to ooze through the region, leading to
somewhat variable but southwesterly winds this morning and
various cloud decks based between 3000 and 5000 ft. With time,
winds are expected to become decidedly westerly by mid-morning
with clouds relegating to aob 20kft. Winds at GYY may trend
northeasterly if a lake breeze were to materialize, as hinted
by some high resolution guidance.

This afternoon, a few showers may attempt to develop ahead of a
cold front, though confidence remains quite low (call it a 20
to 30% chance). Can easily foresee the inherited PROB30 groups
being pulled in a later TAF package as trends dictate.
Otherwise, the cold front will be marked by a modest turn in the
wind direction toward northwesterly.

Overnight, a slackening low-level pressure gradient will allow
for a marine front to push inland off Lake Michigan with an
associated northeasterly wind shift. An area of IFR stratus may
accompany the front, though confidence remains too low to
include anything more than SCT006 in the outgoing TAF. Will let
later shifts evaluate the potential for low clouds further.

Borchardt

&&

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

&&

$$

Visit us at weather.gov/chicago