309
FXUS63 KLOT 020839
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
239 AM CST Sun Nov 2 2025

.KEY MESSAGES...

- Areas of fog early this morning, some of which could be
  locally dense.

- Instances of freezing fog also possible especially near
  the Kankakee River Valley.

- Mainly dry and seasonable conditions expected through the
  middle of the upcoming week.

&&

.DISCUSSION...
Issued at 239 AM CST Sun Nov 2 2025

Through Monday:

An upper low and associated trough continue to drift across the
Ohio and Tennessee River Valleys this morning which is allowing
a mid- level ridge to build into the Great Lakes. As a result
skies have largely cleared out across northern IL and northwest
IN, but a decaying meso-low over southern Lake Michigan
continues to generate some lake effect clouds and showers in
northeast IL. The meso-low is expected to dissipate over the
next 2-3 hours which should allow the ongoing showers and cloud
cover to diminish as well.

Where skies are clear, temperatures have quickly cooled into
the low to mid-30s and are now on par with the dew points. This
has caused some patchy fog to develop across western IL and near
the Kankakee River Valley so far, but as the aforementioned
lake effect clouds erode suspect fog will expand eastward to the
Fox Valley through daybreak. Given the light winds and near
zero temperature-dew point spreads some of the fog will be
locally dense with visibilities of a quarter mile or less.
Additionally, the near freezing temperatures may also result in
some freezing fog especially near the Kankakee Valley. Since
road temperatures are generally in the low to mid-40s slick
spots will be very hit and miss and mainly confined to bridges
and overpasses if they materialize at all. While we are holding
off on a dense fog advisory at this time due to uncertainty in
dense fog coverage, one cannot be ruled out before all is said
and done. Nevertheless, anyone with early morning plans should
use caution and allow extra time to reach their destinations.

Fog will erode by mid-morning giving way to mostly sunny skies
for our Sunday. Winds will also turn southwesterly later this
morning which will advect in warmer air and allow temperatures
to rebound into the mid-50s this afternoon. While these dry and
seasonable conditions are expected to persist through Monday, a
deepening shortwave trough will be moving through the northern
Great Lakes tonight. With moisture expected to be a limiting
factor it appears any associated rain with this system will stay
north and east of our area in WI and MI. However, a stay
sprinkle (15-20% chance) cannot be ruled out near the IL-WI line
or the lake tonight where a pocket of mid-level moisture and
instability will be present. That said, winds will become breezy
tonight through Monday as the pressure gradient tightens
resulting in 20-25 mph gusts, mainly Monday afternoon.

Monday night through Saturday:

A surface high will move into the area Monday night which will
allow the aforementioned gusts to subside. While the high will
establish to our south and east by Tuesday, it is still expected
remain in control of our weather through the middle of the
week. Therefore, near to slightly above normal temperatures
(highs in the upper 50s to lower 60s and lows in the 30s and
40s) are on tap. However, a couple of shortwave troughs are
forecast to swing through the Midwest and Great Lakes regions on
Tuesday and Wednesday respectively. Given the surface high`s
position moisture should continue to be a limiting factor which
should keep any associated rain at bay though a stray sprinkle
cannot be ruled out particularly near the lake on Wednesday.

Our next chance for notable rain does not look to be until
Friday and next weekend when a series of troughs move through
the Great Lakes. Guidance generally remains in decent agreement
on the troughs` evolution and timing, but continue to show
differences in the intensity and track of any associated surface
lows. Thus confidence on what impacts we will see in northern
IL and northwest IN continue to be uncertain at this range. For
now plan on there being some inclement weather in the region to
end the week and stay tuned for more details as we get closer.

Yack

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1239 AM CDT Sun Nov 2 2025

The main aviation weather concerns are:

- Increasing potential for BR/FG (and FZFG) tonight, mainly near
  RFD and perhaps DPA

- Potential for some lingering light showers/sprinkles near the
  lake tonight, mainly INVOF ORD

- Threat for marginal LLWS Sunday night into early Monday
  morning

Lingering lake effect cloud cover and spotty shower activity
will persist tonight at the lake-adjacent terminals. Most
precipitation is expected to remain outside of the 10-mile
rings, however. Winds will range from light northwesterly
(under 8 knots) to light/variable/calm.

Where skies have (or will) clear, fog development is a concern.
At this time, the greatest chances for br/fg development is at
RFD, with more uncertainty regarding cloud clearing trends at
DPA, GYY, and MDW. Have introduced an LIFR TEMPO group for BR
at RFD, but further reductions may be needed, and FZFG
development is appearing increasingly likely. If skies clear at
DPA/GYY, rapid vsby reductions would likely follow towards
daybreak Sunday morning. Will monitor observation and satellite
trends closely tonight.

VFR conditions will return through Sunday morning with
southwesterly breezes. Intermittent gusts into the 15-20 kt
range appear plausible this afternoon, but not over a sustained
enough period to justify adding additional lines at this point.
Winds may ease this evening before gradually increasing tonight
as a LLJ develops overhead. Gustiness will probably re-develop
at ORD/MDW overnight. Currently, LLWS values are a bit marginal
at the Chicago-area terminals and have not introduced a mention
at this time. The LLJ core is expected to be a bit stronger near
RFD, and have introduced a mention there.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 3 PM this afternoon to 10 AM CST
     Monday for the IL nearshore waters.

     Small Craft Advisory from 6 PM this evening to 10 AM CST
     Monday for the IN nearshore waters.

&&

$$

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