080
FXUS63 KILX 061909
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
209 PM CDT Mon Oct 6 2025

.KEY MESSAGES...

- There is a chance of rain (40-60%) this evening and overnight
  with the best chances (60%) along and north of the Illinois
  River Valley and south of I-70.

- A cold front slowly moving across the region will bring a
  return to more seasonable temps (highs in the upper 60s to mid
  70s) north of I-70 Tuesday and area-wide Wednesday though
  Friday.

&&

.DISCUSSION...
Issued at 158 PM CDT Mon Oct 6 2025

This afternoon, a slow moving cold front is draped from near
Milwaukee, WI southwest across Quincy, IL. Dew points in the low
to mid 60s are in place ahead of the front which will contribute
to weak instability along and ahead of the front. 300-500 J/kg
MLCAPE is present in the warm sector this afternoon, and will
further weaken this evening into tonight as the front moves
through. This will limit updraft strength and help keep the severe
threat in check today and tonight. Latest HRRR indicates a couple
waves of showers and storms will be possible, the first late this
evening and the second overnight. 850-300mb heights parallel to
the frontal boundary will promote training as individual
convective elements lift to the northeast around 25-30 mph. 12Z
HREF LPMM indicates a couple SW-NE oriented swaths of relatively
higher precip totals will be possible in the vicinity of the
Illinois River Valley, and shows at least one swath with some
pockets of 2 inches of rain through midday Tuesday. NBM 50th
percentile QPF through midday Tuesday showers around 0.3 to 0.7
inches of rain along and north of the Illinois River Valley with
amounts tapering to just a few hundredths by the I-72 corridor.
Precip amounts have, in general, been trending down with the more
recent model runs.

Meanwhile, water vapor imagery reveals a disturbance lifting north
along the lower Mississippi Valley this afternoon, and this wave
is progged to curve northeast along the Ohio Valley late this
evening and overnight, and will be responsible for some rain
across portions of south and southeastern Illinois. HREF 50th
percentile indicates that a few hundredths of rain will be
possible along the I-70 corridor with amounts picking up to around
0.75 to just over an inch in our far southeast CWA near
Lawrenceville.

In between the cold front approaching from the northwest and the
southern stream shortwave, little if any precip is forecast
between the I-72/Danville corridor and the I-70 corridor.

Surface high will spread from the Upper Midwest across the Great
Lakes Tuesday night into Wednesday, while aloft, mid level height
rises will overspread the Midwest in the wake of departing upper
trough and in advance of a building ridge. This will set the stage
for dry weather to once again prevail across central Illinois
through the latter half of the week. Temperatures will return
closer to the seasonal norms in the northwest flow aloft. Highs
will generally run in the low to mid 70s Wednesday through Friday
while overnight lows will be in the 40s.

A bit of complexity is added to the forecast late Friday into the
weekend as a sharp vort max digs across the Great Lakes with the
disturbance eventually closing off and merging with another area
of low pressure over the southeast CONUS. There is some timing
and track uncertainty with this upper low but it does introduce
some very low but non-zero PoPs into the local forecast Friday
night into Saturday.

Strong upper ridge over the mid section of the country will spread
east to the Mississippi Valley late this weekend into early next
week in the wake of the aforementioned upper low. Temps will once
again surge to well above normal with highs back into the 80s for
much of the area Sunday and Monday. This warmup may be brief,
however, as the upper pattern remains progressive and another
strong trough is progged to lift across the Upper Midwest with an
attendant surface cold front pushing across central Illinois late
Monday into Tuesday. Currently, there looks to be a 20 percent
chance for measurable precip with the front.

Deubelbeiss

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1221 PM CDT Mon Oct 6 2025

Ahead of an approaching cold front, increasing moisture is
resulting in diurnal cumulus mostly above the VFR threshold and
even a couple widely scattered showers. Convective allowing models
(CAMs) suggest those will increase in coverage this evening with
moisture pooling along the front, with the highest probability
(around 30-40%) of a thunderstorm at PIA and BMI. As a low level
inversion sets up to trap boundary layer moisture overnight,
confidence is increasing in a period of IFR stratus with HREF
giving a 70-90% chance at virtually all airfields from 08-14z.
Ceilings should gradually rise into the MVFR category tomorrow
morning, but likely won`t break up until near or after the end of
the forecast period (18z/1pm CDT Tuesday).

Bumgardner

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$