901
FXUS63 KLOT 071131
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
631 AM CDT Tue Oct 7 2025

.KEY MESSAGES...

- Showers and isolated thunderstorms will end from north to
  south this morning.

- Mostly dry weather and seasonable temps remainder of the work
  week; warming temps expected over the weekend.

&&

.DISCUSSION...
Issued at 251 AM CDT Tue Oct 7 2025

Back edge of the showers and scattered thunderstorms will
continue to push steadily southward this morning with rain
ending across majority of the area by mid morning. Skies should
clear out this afternoon, but despite the sunshine, it`ll be
much cooler today with highs generally in the 60s.

Weak secondary cold front will move south down the lake tonight
and across our CWA late tonight/early Wednesday morning. Only
impact from this front is expected to be a modest increase in
lake induced instability with a modest rise in inversion
heights. This will likely lead to lake effect stratocumulus
streaming in off the lake into northeast IL with some potential
for a few sprinkles. Given the dry air mass and marginal
thermodynamics, kept formal mention of sprinkles out of the
forecast, but did bump up pops in the gridded database to
10-14% near the lake between about 09-15z Wed.

Generally dry conditions are expected through the upcoming
weekend. Guidance still has a weak clipper-like system moving
across the region in the Friday-ish time frame, but with limited
moisture and current guidance keeping the system pretty weak,
have maintained a dry forecast. Sometimes these low amplitude
systems in the medium range can end up a bit stronger than
progged, if that were to happen and if it were to track just
right, couldn`t rule out a shower threat Friday in the area, but
chances too low to include in the forecast.

Temperatures will return to above average over the weekend as
upper ridging spreads east and warm air advection ramps up ahead
of developing cyclone over the Plains by late in the weekend.
That system will eventually move eastward bringing rain chances
into our area early next week as it does.

- Izzi

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 631 AM CDT Tue Oct 7 2025

Main Concerns:

- MVFR VSBY at times before rain ends by mid to late this
  morning at the Chicago metro terminals.

- Low CIGs improving, especially this afternoon.

Most of the rain with any reduced VSBY impacts (2-5SM) will end
by 13-14z at the Chicago metro terminals, though occasional VFR
SHRA may persist until 15-16z, latest at GYY. Current IFR CIGs
(LIFR at GYY) should improve to MVFR by mid to late morning and
then VFR by early afternoon, except hanging on a bit longer at
GYY. Northerly winds of ~10-12 kt ranging from 350-020 degrees
will gust to near/around 20 kt near the lake until diminishing
with sunset. Expect direction to shift to NNW/NW after sunset
and then to return to northeast early Wednesday. Can`t rule out
a period of higher end MVFR CIGs Wednesday morning.

Castro

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 PM CDT Wednesday for the IL
     nearshore waters.

     Small Craft Advisory until 10 AM CDT Wednesday for the IN
     nearshore waters.

&&

$$

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