368
FXUS63 KLOT 081951
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
251 PM CDT Wed Oct 8 2025

.KEY MESSAGES...

- Patchy frost expected tonight in typically colder, rural
  locations, especially across northwest Indiana.

- A growing signal for some light rain on Friday, otherwise
  generally dry with seasonable temps through the upcoming
  weekend.

&&

.DISCUSSION...
Issued at 250 PM CDT Wed Oct 8 2025

Early this afternoon, a scattered cumulus deck is building off
the lake and extending SW across much of the CWA, while
elsewhere remains mostly sunny. Temperatures are nearing their
highs for the day in the lower and middle 60s. Localized cloud
cover may continue to develop over the lake through the night,
but coverage should be largely limited to communities near the
IL lakeshore. A big majority of our CWA will see mostly clear
skies through the night. Sitting comfortably within a broad
surface trough, winds tonight will also be light to near calm
with dry boundary layer air. This is a prime setup to favor the
cooler side of guidance overnight, which would result in lows in
the middle to upper 30s around the suburbs and outlying areas
while 40s are expected in the city and around the interior metro
area. The coolest conditions should largely be found around our
NW Indiana counties where temps may fall to just above
freezing. Similar conditions are expected on more of a localized
basis across rural areas of northern IL. Accordingly, made the
decision to hoist a Frost Advisory for our five Indiana counties
from 3AM/4AM to 8AM/9AM CDT/EDT where greater coverage of frost
is attainable away from the lake. Frost coverage will be more
patchy elsewhere and primarily confined to outside of the
Chicago metro.

Tomorrow will be very similar to today with highs in the middle
and upper 60s beneath mostly sunny skies. Attention in the
forecast then turns to a tightly wound upper low that will clip
the region on Friday. The low is expected to close up north of
the Great Lakes late Thursday and track southeast into the the
upper Ohio Valley by Saturday. The storm`s cold front will get
dragged across the CWA Friday into Friday night. Ensemble PoPs
around the area have been on a consistent upward trend run by
run, but probabilities for measurable precip remain considerably
low, largely in the 10 to 30% range. With the cooler mid level
air staying out of reach to our north and a dry PBL on forecast
soundings, instability will be low to absent. Moisture looks
rather shallow as well, but ample enough to stir up some light
showers amid some noteworthy omega ahead of the advancing low.
The NBM populated the forecast with only slight chances near our
north, which was maintained for now. Those may have to be
bumped up or expanded though in the coming days, but brief and
likely lighter showers are probably all we`re looking at for
Friday.

Friday could also feature a good breeze, especially in our
north and northwest, as we mix into a decent LLJ. There is
support for 20 to even near 30 mph gusts, but there is still
some uncertainty. For now, boosted the forecast from the NBM to
get some near 20 mph gusts up that way, but these may need to be
bumped even further as confidence grows. If the rain holds out
and winds perform to their fullest, a localized elevated fire
risk may even be in the cards in our west and northwest on
Friday.

For the past couple of days now, medium range deterministic and
ensemble guidance has been trending cooler behind the front on
Friday which may have implications for temperatures this weekend.
Forecast highs for Saturday and Sunday have been on a steady
downward trend. While there still is some uncertainty and
support for warmer conditions, highs in the 60s around the metro
are looking more likely with time, especially on Saturday.
Lower 70s may be more attainable across outlying areas. Sunday
should be a tad warmer with some southerly return flow kicking
in late Saturday. For Sunday the forecast is now calling for 50s
downtown through mid- morning and peaking in the middle 60s.

More uncertainty lingers into next week, but slightly warmer-
than-average conditions are favored for at least the first half
of the week. Another, much larger synoptic system looks to clip
the region early next week introducing slightly higher precip
chances to the forecast, but there remains no solid signal for a
healthy widespread rain over the next seven days.

Doom

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1227 PM CDT Wed Oct 8 2025

VFR conditions are forecast through the period. Northeast to
east winds around 10 kt will continue through the afternoon.
Winds ease after sunset becoming light and variable overnight
and settle into a prevailing southeast direction after daybreak
Thursday.

Scattered to broken VFR lake effect clouds are expected at
times through this evening near the lake, otherwise mostly
clear skies are expected through the rest of the period.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Frost Advisory from 3 AM CDT /4 AM EDT/ to 8 AM CDT /9 AM EDT/
     Thursday for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...None.

&&

$$

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