428
FXUS63 KLOT 032334
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
634 PM CDT Fri Oct 3 2025

.KEY MESSAGES...

- Summer-like warmth will continue through the weekend.

- Heightened fire weather danger is expected on Sunday (see
  Fire Weather section below).

- A slow-moving cold front will likely bring rain to the area
  early next week, followed by cooler, more seasonable
  temperatures.

&&

.DISCUSSION...
Issued at 313 PM CDT Fri Oct 3 2025

Through next Friday:

It`s been a balmy day for early October standards around here
today with upper 80s temperatures, and even a few 90F
observations, being noted on area ASOS/AWOS readings this
afternoon. The vast majority of the area has remained dry for
yet another day as well, with the exception of a few locales
south of the Kankakee River, where in spite of minimal upper-
level forcing support and somewhat limited low-level moisture,
a few isolated showers have managed to pop within a
shear/deformation axis. Couldn`t rule out some isolated
lightning with this activity if any of these cells managed to
grow as deep as some of the cells farther downstate have this
afternoon. However, with the slightly better dew points and
instability expected to remain to our south through sunset,
think that the probability of lightning occurring in our
southern CWA remains less than 15% at any one location. That
said, spotty shower activity may still continue in locations
near and south of the Kankakee River Valley through sunset (and
possibly beyond), so have slight chance PoPs going into this
evening for those locales to account for this.

Our stretch of unseasonable warmth will extend into the weekend
as expansive surface high pressure stationed along the Atlantic
Coast will continue to promote ample sunshine and southerly
winds across the Lower Great Lakes. Saturday into Sunday, an
upper-level trough will eject from the Rocky Mountains into the
northern Plains and Upper Midwest, spurring the development of a
surface low that will track northeastward across the Dakotas
and northern Minnesota into western Ontario. The southerly winds
in our area will become increasingly breezy in response to the
tightening pressure gradients between this deepening cyclone and
the nearly stationary Atlantic Coast high. With how dry we`ve
been recently (and still will be this weekend), these stronger
winds will yield heightened fire weather concerns on Sunday. For
more information on that, reference the Fire Weather section of
the AFD below.

The cold front associated with the aforementioned surface low
will continue to progress eastward/southeastward going into the
work week, though its forward motion will decelerate as it
becomes increasingly removed from the low`s center, which is
likely to be in northern Quebec come Monday. As a result, Monday
looks like it will be another warm day across much of the area
with temperatures likely to climb into the 80s once again
everywhere except for our far northern CWA and possibly some
locations along the lakefront (pending how quickly the cold
front arrives). A period of rain also appears probable sometime
Monday into Tuesday as the divergent right entrance region of a
100+ kt upper-level jet overlaps the slow-moving frontal zone
as it crawls across the area. While any rain will be welcome
given our recent dry spell, it is not yet clear whether our
rainfall totals from this will end up being substantial enough
to meaningfully cut into our rainfall deficits and provide
noticeable relief to the burgeoning drought.

Cooler, more seasonable temperatures behind the cold front will
then settle into the region for the middle part of the upcoming
week. Precipitation will also cease as surface high pressure
overspreads the Midwest in the front`s wake. Ensemble
consistency in the upper-level pattern evolution and
configuration then breaks down late next week, so confidence in
the forecast is markedly lower for the end of the week going
into next weekend at this time.

Ogorek

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 634 PM CDT Fri Oct 3 2025

There are no significant forecast concerns this period. A lake
breeze just east of ORD/MDW will dissipate soon with sunset.
Wind directions are expected to turn light south/southeast for a
few hours this evening then turn back to light south/southwest
overnight. Winds at some locations will likely become light and
variable or calm. Southwest winds will increase after sunrise
Saturday morning with speeds into the 10-12kt range by midday
and gusts to 20kt through afternoon. Speeds/gusts will diminish
with sunset Saturday evening with directions turning back
southerly.

Isolated showers well south of the terminals are expected to end
this evening. However, there will remain a small chance for an
isolated shower well south of the terminals overnight into early
Saturday morning. cms

&&

.FIRE WEATHER...
Issued at 313 PM CDT Fri Oct 3 2025

Unseasonably warm and dry conditions are expected this weekend.
Given the worsening short term drought, this will result in a
heightened fire danger, particularly on Sunday when winds
should pick up a bit.

Mostly sunny skies with temperatures solidly in the 80s are
expected on Saturday and Sunday afternoons. Considerable spread
remains in forecast guidance regarding surface dew points and
resultant relative humidity values. Based on the latest available
forecast guidance, the NBM`s dew points are still probably too
high when taking into account the recent very dry conditions and
the expected relatively deep mixing, so have lowered them a bit
once again (though still possibly not by enough). Our latest
forecast still has minimum afternoon RH values in the 30-40%
range Saturday afternoon and in the 25-35% range Sunday
afternoon, though it remains plausible that RH values could end
up being a bit lower than this.

Winds will pick up a bit on Saturday, but more so on Sunday with
20ft winds increasing to 10-20 mph with some gusts around 25 mph
at times in the afternoon. Given the recent dry spell and
vegetation growing increasingly dormant, Sunday does look to have
a heightened fire weather danger, though conditions still look
like they`ll remain shy of red flag criteria.

- Izzi/Ogorek

&&

.CLIMATE...
Issued at 459 AM CDT Fri Oct 3 2025

High temperatures could approach the record highs for the day,
here are the current records for October 3:

            Today        Saturday       Sunday
Chicago    91 (1954)     90 (1951)     88 (1997)
Rockford   90 (1997)     90 (1922)     90 (1922)

- Izzi

&&

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

&&

$$

Visit us at weather.gov/chicago