East Dundee, Illinois Weather Forecast Discussion

656
FXUS63 KLOT 030828
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
328 AM CDT Fri Oct 3 2025
.KEY MESSAGES...
- Summer-like warmth expected today through the weekend
- Heightened fire weather danger Sunday (see Fire Weather
  section below)
- Slow moving cold front will bring rain chances early next week
  with more seasonable temperatures in the wake of the front
&&
.DISCUSSION...
Issued at 328 AM CDT Fri Oct 3 2025
Today and the upcoming weekend will feel more like July than
October with unseasonably warm temperatures likely. Guidance is
in good agreement on showing 925mb temps 1.5-2C warmer than
Thursday afternoon, which should equate to high temps 2-4F
warmer than Thursday. That should result in highs mostly in the
upper 80s with some lower 90s, especially western CWA.
A weak/weakening upper low can be seen on water vapor imagery
near STL early this morning. This upper low is expected evolve
into more of a shear axis across central IL into eastern MO this
afternoon. There is some support from CAMs for isolated showers
and thunderstorms this afternoon in the vicinity of this
shear/deformation axis. While this can`t be ruled out, most of
the guidance that is convecting also has dewpoints in the 60s
with more instability. Given the worsening drought/dry
conditions, seems likely that dewpoints will mix out into the
50s this afternoon, limiting instability. In addition, water
vapor imagery shows drier air aloft advecting eastward into the
area, so rain chances look meager. Opted to keep the forecast
dry in our area this afternoon, but did raise pops to around 10%
near/south of the Highway 24 corridor this afternoon where
there is the best chance for isolated convection.
This weekend should be dry and continued unseasonably warm.
There is good model agreement in 925mb temps inching downward
Saturday and Sunday, so today will probably be the warmest day
with temps a couple of degrees cooler (well less hot) this
weekend, but still well into the 80s. A weak lake breeze will
keep temps a bit cooler right along the immediate Illinois shore
today, but stronger southwest winds should push the warmth
right up to the lakefront over the weekend.
A trough will push east across the Northern Plains and into the
western Great Lakes early next week. This should help drive a
cold front across our area and bring an end to our summer-like
temperatures. There are some timing differences in medium range
guidance with the slower ECMWF solution likely allowing for
another unseasonably warm day in the 80s CWA-wide Monday, while
the GFS is a bit faster with the front and would keep temps
cooler northern CWA.
Anafrontal nature of the cold front looks to result in the best
precipitation chances being post-frontal Monday night driven by
the strong forcing for ascent in the right entrance region of
>100kt upper level jet. Opted to leave NBM pops as-is with high
end chance to low end likely pops, but it`s worth keeping the
old adage of "when in drought, leave it out" in mind when
looking at guidance with more significant rainfall. There is
some model support for some decent rainfall totals, but the more
conservative NBM pops are the way to go for now.
A transition to cooler (well actually more seasonable)
temperatures is expected in the wake of the front and rain
potential Tuesday through Thursday next week. By later next
weekend, medium range ensemble guidance favors a digging trough
over the eastern U.S. with an amplifying ridge over the central
portions of the country. The GEFS is farther west with the
trough and would favor near/below average temps, with the ECMWF
farther east with the ridge/trough around would mean a return to
above average temperatures. NBM guidance offers a reasonable
compromise with temps moderating some late in the week, but the
notable differences in guidance does mean lower than average
forecast confidence.
- Izzi
&&
.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1205 AM CDT Fri Oct 3 2025
VFR with no significant concerns through the period.
Light southerly to calm/VRB winds through early this morning
will become southwesterly near 10 kt by the mid to late morning
at northern IL terminals. A lake breeze may approach MDW and
perhaps ORD after sunset. Given that timing, the boundary will
probably wash out, with winds returning to light southerly
through Friday night. Even if the lake breeze reaches MDW and
ORD, (unless it were to push inland quicker and reach the
terminals prior to sunset), speeds from the southeast or east-
southeast will likely be safely below 10 kt. Any very spotty
SHRA on Friday should be south of the terminals.
Castro
&&
.FIRE WEATHER...
Issued at 328 AM CDT Fri Oct 3 2025
Unseasonably warm and dry conditions are expected this weekend,
which given the worsening short term drought, will result in a
heightened fire danger, particularly Sunday when winds should pick
up a bit.
Mostly sunny skies with temperatures in the 80s are expected both
Saturday and Sunday afternoons. There is considerable spread in
forecast guidance regarding surface dewpoints and resultant
relative humidity values. Given the recent very dry conditions
and expected relatively deep mixing, have lowered forecast
dewpoints considerably from the NBM, but still not as low as some
guidance would support. Current forecast has min afternoon RH
values in the 30-40% range Saturday afternoon and 25-35% range
Sunday. Plausible that RH could be lower, but given some guidance
has RH considerably higher, didn`t feel comfortable getting too
aggressive with the lowering of dewpoints. Will be interesting to
watch how dewpoints behave this afternoon, as this could
potentially give us a clue as to how low dewpoints will mix out
this weekend.
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 look to remain
well shy of red flag criteria.
- Izzi
&&
.CLIMATE...
Issued at 328 AM CDT Fri Oct 3 2025
High temperatures could approach the record highs for the day,
here are the current records for October 3:
Chicago:  91 (1954)
Rockford: 90 (1997)
- Izzi
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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