Flag Center, Illinois Weather Forecast Discussion

367
FXUS63 KLOT 051941
AFDLOT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
241 PM CDT Sun Oct 5 2025
.KEY MESSAGES...
- Stronger winds and continued dry conditions will continue to
  result in heightened fire danger and areas of blowing this
  afternoon.
- July-like warmth continues for much of the area on Monday.
- A cold front will bring rain chances and some thunderstorms
  Monday afternoon and night.
- Dry conditions and more seasonable temperatures are in store
  mid to late week.
&&
.DISCUSSION...
Issued at 241 PM CDT Sun Oct 5 2025
Elevated fire weather concerns will persist for a few more
hours this afternoon due to dry conditions and gusty southerly
winds. RH values have fallen as low as 25 percent across the
southern CWA while winds have gusted up to 30 mph across
northern Illinois. The associated Special Weather Statement for
elevated fire weather conditions remains in effect through 6pm
CDT.
A deep trough over south-central Canada will track eastward
across northern Ontario through Tuesday. An associated cold
front stretching from northern Minnesota to western Kansas will
track southeast across the area Monday into Monday night,
bringing our first notable chance of rain in nearly two weeks.
The initial chances for precip will occur with isolated mid-
level showers brushing the northwest CWA late tonight into
Monday morning. However, precip at the surface will remain
sparse and light as the showers evaporate through a rather dry
sub-cloud layer.
Poor mid-level lapse rates and diurnal mixing in the warm
sector across the southeast half of the CWA ahead of the front
will limit intensity and coverage of precip, but with the
environment expected to be mostly uncapped, could see some
attempts at isolated thunderstorm during the afternoon. Farther
northwest, low-level forcing along the front (albeit with
overall weak convergence) will provide an impetus for isolated
to scattered showers and some thunderstorms during the
afternoon. Mixing should erode MLCAPE values while mid-level dry
air induces decent entrainment of cells, but appreciable deep-
layer shear and freezing levels around 10kft will support the
potential for small hail and gusty winds with any stronger
shower/storm.
As higher low and mid-level moisture advects toward the area
this evening and especially overnight, larger scale ascent from
the right- entrance region of a slow-moving jet core will
enhance shower/rain coverage and intensity. With a modestly
strong low-level f-gen signal along the front and marginal mid-
level lapse rates above the LPL, narrow bands of heavy rain with
embedded storms are possible. The coverage of heavy rain bands
will be low, so widespread beneficial rain to partially
alleviate the growing drought does not appear likely.
After the rain ends from north to south on Tuesday, dry
conditions are favored through the remainder of the week and
potentially through next weekend as a broad, low-amplitude ridge
settles across the central CONUS. However, a moisture-starved
impulse tracking southeast across the ridge could bring a few
high based showers or sprinkles late Thursday night into Friday.
Otherwise, seasonable temperatures midweek will gradually
moderate back to above normal to well-above normal temperatures
for the weekend.
Kluber
&&
.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1203 PM CDT Sun Oct 5 2025
VFR conditions expected through the 24-30 hour TAF period.
Gusty south-southwest winds will continue to be the primary
weather story through the afternoon. Peak gusts should top out
between 25-30kt. Expect the gustiness to abate with sunset
early this evening.
Southwest winds will continue on Monday in advance of an
approaching cold front. This cold front is expected to shift
across the terminals sometime in the 21 to 00Z timeframe Monday
afternoon. A northerly wind shift will accompany the front, and
the threat for showers (and a few possible thunderstorms) will
increase into early Monday evening. With this potential period
of weather coming right at the end of the 30 hour ORD and MDW
tafs, I opted to add the wind shift after 22Z along with a
Prob30 group for a couple hours for showers. The threat of
showers will increase after 00Z Tuesday, so expect future
forecasts to have a continued mention into Monday evening and
night.
KJB
&&
.FIRE WEATHER...
Issued at 242 AM CDT Sun Oct 5 2025
No change in thinking regarding potential fire weather concerns
this afternoon. Stronger winds today will combine with the very
warm and dry conditions to result in an elevated fire weather
danger, particularly over Illinois. In addition to the stronger
winds, it continues to look favorable for dewpoints to mix out
this afternoon, resulting in min afternoon RH values between 20
and 30 percent.
The forecast still largely keeps conditions below Red Flag
Warning criteria. However, with conditions probably nearing
Red Flag criteria for a couple/few hours this afternoon, will
reissue the SPS to advertise the heightened risk of field,
brush, and grass fires getting out of control.
- Izzi/KJB
&&
.CLIMATE...
Issued at 242 AM CDT Sun Oct 5 2025
High temperatures may approach record highs this afternoon.
Here are the current records for October 5th:
Sunday
Chicago    88 (1997)
Rockford   90 (1922)
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 10 PM CDT this evening for the IL
     nearshore waters.
&&
$$
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NWS LOT Office Area Forecast Discussion