723
FXUS63 KLOT 040555
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1255 AM CDT Wed Jun 4 2025

.KEY MESSAGES...

- A band of showers and some thunderstorms will move eastward
  across the area through Wednesday.

- Trending drier with seasonable to seasonably cool conditions
  late this week and into the weekend.

&&

.DISCUSSION...
Issued at 347 PM CDT Tue Jun 3 2025

Through Wednesday:

Please reference the mesoscale discussion above for information
about the strong to severe thunderstorm potential this evening.

After the MCS decays this evening, an elongated band of rain
streaming northeastward across an eastward-inching frontal zone
will persist in our forecast area through the overnight hours
and into the daytime tomorrow. Some embedded lightning could
occur late this evening into the overnight hours, but in
general, the overall likelihood of lightning will continue to
steadily diminish through the night and into tomorrow morning.
Areas still near and south of the true cold front by mid-day
tomorrow (likely locations south of I-80, but especially
locations south of the Kankakee River) should then see a
renewed potential for thunderstorms during the afternoon as pre-
frontal warm air advection and filtered sunshine contribute to
diurnal destabilization. Questions still remain regarding
whether the better instability will get as far north as our
southeastern CWA. If it does, then couldn`t rule out a strong
storm or two occurring in our southeastern counties, but the
overall better chances for this should remain to our south and
east.

Otherwise, fall-like conditions can be expected tomorrow north
of the cold front with anafrontal rain, stratus, and
temperatures largely in the mid 50s to mid 60s. The rain and low
clouds should clear out faster in our far northern CWA
(including in the Rockford area), which could allow daytime
temperatures there to climb into the low 70s. However, smoke
models indicate that another plume of Canadian wildfire smoke
should descend into the area behind the anafrontal rain, which
will lead to hazy skies once again wherever the stratus has
cleared out, and could potentially result in some smoke
concentrations being observed at ground level once again as well.

Ogorek


Wednesday Night through Monday:

Wednesday`s cold front will continue to sag southward Wednesday
night, with the remaining southeast portions of the CWA cleared
of the front by mid-evening and remaining showers after
midnight. The front will settle just north of the Ohio River
Valley by Thursday morning as surface high pressure drifts
across the Upper Great Lakes. This will favor a dry and mostly
sunny day on Thursday with highs in the mid to upper 70s inland
and 60s along the lake.

Consensus guidance is for a wave across the central Rockies to
pickup or absorb at least some energy from an upper-level low
over the southwest U.S. Wednesday into Thursday. A weak surface
low developing from convective feedback over the central Great
Plains Thursday evening will traverse the front on Friday.
Guidance has come into somewhat better agreement that the main
impacts from this system developing along the front will remain
south of much of the forecast area, though some showers could
brush the southern CWA Friday afternoon and evening. Otherwise,
seasonably cool conditions under partly to mostly cloudy skies
can be expected on Friday.

High pressure across the Upper Mississippi River Valley on
Saturday will produce seasonable conditions and dry weather. An
upper-level low over the far northern Great Lakes will then push
a cold front with the potential for showers and a few storms
across the area late Sunday into Monday morning.

Kluber

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1255 AM CDT Wed Jun 4 2025

SW winds around 10 knots with a few gusts nearing 20 knots at
TAF issuance will shift NE/NNE up to 10 knots with the passage
of a cold front roughly around 12Z for ORD/MDW. Winds will then
remain NNE at 10 knots or less through the remainder of the
period.

RA/SHRA along and behind the cold front will also bring quickly
lowering ceilings. IFR ceilings have already spread to RFD,
with additional upstream IFR ceilings across southern Wisconsin
expected to spread over the Chicago terminals around or shortly
after sunrise. Isolated -SHRA currently around northeast
Illinois will increase in coverage and intensity during the pre-
dawn hours and may result in periods of IFR/MVFR visibility with
the strongest showers. TS remains possible with these SHRA in
the 09-12Z window, but chances of under 20 percent preclude
mention in the TAF at this time.

Ceilings are expected to gradually improve into MVFR levels
late this morning and especially this afternoon. Fog may develop
over Lake Michigan and slowly advect inland today and tonight.
While diurnal heating should scatter the lowest layer of
ceilings associated with any fog during the afternoon, IFR
ceilings could return this evening and persist into the
overnight hours.

Lastly, wildfire smoke has resulted in MVFR visibility well
upstream into western Wisconsin and northeast Iowa. If the
higher concentrations upstream continue to persist with time
today, lower visibility from HZ/FU may need to be included
beginning late this afternoon at the Chicago terminals. Have
already included 6SM for RFD, but this value would need to be
lowered as well.

Kluber

&&

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

&&

$$

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