Lansing, Illinois Weather Forecast Discussion

175
FXUS63 KLOT 242332
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
632 PM CDT Wed Sep 24 2025
.KEY MESSAGES...
- A few lake effect showers can`t be ruled out near the lake
  overnight into Thursday morning (20-30% chance).
- Drier conditions are expected to end the week as temperatures
  inch back into the 80s over the weekend.
&&
.DISCUSSION...
Issued at 248 PM CDT Wed Sep 24 2025
Through Thursday Night:
A broad upper low continues to spiral over northern MI and is
starting to phase with the shortwave trough traversing across
eastern KS and MO. While northern IL and northwest IN are
sandwiched between these features and under some broad ascent,
mid-level moisture is somewhat sparse which has allowed for
drier conditions to prevail and this is expected to remain the
case through tonight for most. That said, there are a couple of
showers trying to develop along a frontal boundary in central IL
which may briefly brush our southern CWA through sunset. Hence
a 20% chance for isolated showers has been maintained for areas
along and south of a Pontiac to Rensselaer line. Additionally,
there remains the chance for some lake effect showers to develop
tonight into Thursday morning as a vort max (currently over
northern Lake Michigan) pivots through the area. With the upper
low being analyzed a bit further east than originally thought
the lake induced instability does not seem to be as impressive
as guidance suggested yesterday so suspect coverage of lake
effect showers will be rather spotty. Nevertheless, the 7000-
8000 ft deep moisture profiles and stout convergence still looks
to be sufficient to maintain the 20-30% POPs along the IL and
northwest IN lake shores.
Any lake effect showers that do materialize tonight will
gradually pivot into northwest IN Thursday morning and then exit
by midday. Therefore, Thursday looks to be a dry day with
otherwise partly cloudy skies. Though, the breezy northwest
winds will keep temperatures on the more seasonable side with
highs in the low to mid-70s.
Friday through Wednesday:
The previously advertised upper ridge will be building into the
Great Lakes as we head into Friday and persist through at least
the middle of next week. As a result, dry conditions will once
again dominate the forecast with south-southwest winds advecting
in more above average temperatures to close out September. So
expect highs during this period to be in the upper 70s to
mid-80s each day with overnight lows in the mid-50s. While a
weak cold front is still expected to swing through the area late
Sunday into Monday, the lack of moisture and cold air with it
look to offer little change to the forecast. However, the front
will allow winds to favor a more easterly direction and make it
more favorable for daily lake breezes to move onshore Monday,
Tuesday, and Wednesday. Thus temperatures near the lake these
days will be a bit cooler in the low to mid-70s.
Yack
&&
.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 632 PM CDT Wed Sep 24 2025
Steady north to northeast winds are expected to ease after
sunset and return to a northwest direction in Illinois overnight
through Thursday morning. Hi-res guidance continues to support
an inland push of the lake breeze in the afternoon turning
winds back to the northeast/east at GYY/MDW and potentially at
ORD. Opted to not make changes to this just yet as there may
continue to be subtle changes in timing and inland extent.
A few sprinkles can`t be ruled out as far west as MDW/ORD but
the trend has been toward the weak lake effect shower band
setting up farther east into northwest Indiana. Have added a
VCSH mention at GYY with associated MVFR ceilings Thursday
morning to account for this.
Patches of MVFR stratus/strato-cu can`t be ruled out this
evening and again early Thursday morning for the Illinois
terminals as well but confidence remains too low to include
with this update. Will continue to monitor satellite and
observational trends.
Lastly, given sufficient clearing to allow for radiational
cooling, patchy MVFR BR can`t be ruled out toward RFD late
tonight into early Thursday morning.
Petr
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement through Thursday morning for ILZ006-
     ILZ103-ILZ104.
IN...Beach Hazards Statement through Thursday afternoon for INZ001-
     INZ002.
LM...Small Craft Advisory until 7 AM CDT Thursday for the IL
     nearshore waters.
Small Craft Advisory until 7 AM CDT Thursday for the IN
     nearshore waters.
&&
$$
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NWS LOT Office Area Forecast Discussion