474
FXUS63 KILX 081141
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
541 AM CST Mon Dec 8 2025

.KEY MESSAGES...

- The next potential for frozen precipitation will come into the
  picture on Thursday when a weak system will bring a 30% chance
  for light snow.

- Another surge of very cold air is expected by the end of the
  week...resulting in sub-zero apparent temperatures Friday night
  through Sunday.

&&

.SHORT TERM... (Today through Tuesday)
Issued at 240 AM CST Mon Dec 8 2025

08z/2am surface analysis shows high pressure extending from
Ontario southwestward to Texas. Thanks to a dry N/NE boundary
layer flow around the high, skies have cleared across the majority
of central Illinois...with the exception being south of I-70 and
across the far SW KILX CWA around Jacksonville/Winchester. The
partial clearing will allow early morning lows to dip into the
single digits north of I-72...with 20s noted south of I-70 where
clouds will be slowest to depart. Meanwhile further west, a subtle
short-wave trough tracking across eastern Nebraska/western Iowa is
creating a mid-level cloud deck and even a few reports of snow
flurries west of the Mississippi River. As this feature pushes
eastward, skies will once again become overcast from west to east
across the area by dawn or shortly afterwards. Based on upstream
obs, have added scattered snow flurries to the forecast...mainly
along/west of the I-55 corridor this morning. As the wave
dissipates and/or exits into Indiana, partial clearing will be
observed this afternoon. High temperatures will mostly be in the
middle to upper 20s...with lower to middle 30s noted south of
I-70.

As the ridge axis shifts into the Ohio River Valley, a
southwesterly return flow will develop tonight. As a result, am
expecting low temperatures in the teens and lower 20s to be
achieved in the evening...followed by readings slowly rising into
the middle to upper 20s overnight. The next storm system embedded
within the prevailing northwesterly flow pattern will approach on
Tuesday. As has been seen by the past several model runs, the
short-wave and its associated surface low will track well north
of Illinois Tuesday night into Wednesday. As the pressure gradient
tightens ahead of the low, southwesterly winds will gust to
around 20mph late tonight into Tuesday. This will help push late
afternoon highs into the upper 30s and lower 40s, with readings
climbing into the middle 40s Tuesday evening as strong WAA
continues. While the bulk of the precipitation associated with
this system will stay across Wisconsin/Iowa eastward into the
Great Lakes, a few rain showers may be observed as far south as
central Illinois Tuesday night. Have carried rain chances
everywhere, but have continued to focus the highest PoPs (50-60%)
north of the I-74 corridor.

Barnes

.LONG TERM... (Wednesday through Sunday)
Issued at 240 AM CST Mon Dec 8 2025

Once the low tracks into the Great Lakes, northwesterly flow will
bring cooler air back into the region on Wednesday. High
temperatures will range from the middle to upper 30s north of
I-72...to the middle to upper 40s south of I-70. These readings
will be observed during the early morning, followed by slowly
falling temperatures for the remainder of the day. Scattered light
rain showers will occur...possibly mixing with or changing to snow
showers as far south as a Decatur to Paris line during the morning
before dry weather returns during the afternoon.

After a cold/dry night Wednesday night, the forecast becomes a
bit more challenging for the end of the week. Models continue to
struggle with the timing and track of the next short-wave trough
slated to impact the region. The 00z Dec 8 GFS continues to bring
a swath of light snow across the heart of central Illinois on
Thursday. Meanwhile the GEM keeps the snow further southwest
mainly across Missouri into southern Illinois and the ECMWF brings
little more than a few snow flurries to the area. Given the fact
that a substantial storm system will have just traversed the
region Tuesday night into Wednesday, am skeptical of the GFS
solution suggesting a light accumulation of snow on Thursday.
Moisture will be limited and no significant upper wave is noted,
so am leaning toward the ECMWF solution. As a result, will limit
PoPs to just 30% and will continue to monitor future model runs
before adding much snow for Thursday.

The main late week weather story continues to be the next surge of
bitterly cold air from Canada slated to arrive Friday through the
weekend. Think snow showers will accompany passage of an Arctic
cold front on Friday...followed by very cold and dry weather over
the weekend. Highs will be in the 20s on Friday, but will remain
in the teens both Saturday and Sunday. The 00z NBM indicates a
40-60% chance of low temperatures dropping below zero along/north
of a Quincy to Terre Haute line Friday night...with similar
probabilities noted Saturday night as well.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 541 AM CST Mon Dec 8 2025

VFR conditions will prevail through the entire 12z TAF period. A
5000-10000ft cloud deck is currently spilling into the Illinois
River Valley and will spread eastward to KCMI by 15z. These clouds
will shift further east and dissipate as the day progresses, with
mostly high clouds remaining by mid to late afternoon. NAM forecast
soundings maintain just high cloudiness tonight: however, the
HRRR is hinting at potential MVFR clouds forming across the W/NW
terminals toward dawn Tuesday as warm advection increases. Will
leave the low ceilings out of the forecast for now...pending
further evidence from future model runs and observational trends.
Winds will initially be N/NE at less than 10kt this morning, then
will become SE during the afternoon. As the pressure gradient
tightens ahead of an approaching low, winds will veer to SW and
gust 15-20kt after midnight.

Barnes

&&

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

$$