485
FXUS63 KILX 111121
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
521 AM CST Tue Nov 11 2025

.KEY MESSAGES...

- Breezy today with southwesterly winds gusting 25-35 mph. There
  is a low chance (10-30%) for gusts as high as 40 mph.

- A gradual warming trend begins today and continues through
  Saturday. Highs today will range from low 40s in east-central
  Illinois to low 50s in west-central Illinois. By Saturday, there
  is a high chance (75-90%) of temperatures reaching the 70s.

&&

.DISCUSSION...
Issued at 119 AM CST Tue Nov 11 2025

*** TODAY ***

A NW flow pattern is in place aloft, with a developing upper ridge
over the SW US and deep troughing centered over New England. A
weak shortwave traversing the NW flow was located over the Dakotas
as of 1am/07z, with upper level cloud cover streaming well
downstream. Expect increasing cloud cover leading to mostly cloudy
skies through this morning, followed by decreasing cloud cover in
the afternoon. Fcst soundings continue to show a well-saturated
layer aloft, so this will be a rather thick cloud deck. Bases are
expected to be 8- 10 kft above the sfc though, and with dry low-
level air it will be difficult for any precip to reach the sfc.
Despite my skepticism, did leave a mention of isolated flurries in
the forecast through midday.

A tight pressure gradient will exist today between strong sfc high
pressure (around 1032mb) near the Gulf Coast and a 996 mb sfc low
over Ontario. This will result in breezy SSW winds today, with a
high chance (over 80%) of peak gusts of 30-35 mph. GFS fcst
soundings suggest even higher gusts (over 40 mph) could mix down,
but will note this is a bit of an outlier, even when comparing
with the GEFS members (generally 25-35 mph gusts). HREF probs only
have a 10-25% chance for gusts over 40 mph. Afternoon relative
humidity drops to around 30-35%, which combined with the gusts
could lead to some minor risk of unwanted fire spread.

The only other notable forecast challenge in the short-term is the
impact of snow cover in east-central IL on the temperature
forecast. The low temp forecast for this morning was lowered into
the teens, and current obs are around 20 degrees over snow cover
compared to mid 20s elsewhere. Not confident as to how much snow
cover will limit temps today given the breezy southwest winds, but
did nudge the forecast a few degrees cooler over the snow cover.
Forecast highs range from upper 40s/low 50s west of I-55 to near
40 in areas of snow. Lows tonight will be near freezing.

*** REST OF THE WEEK ***

Upper ridging gradually amplifies out west and slides east by the
late week period, and the warming trend is little changed from
previous forecasts. Highs on Wed-Thurs will be closer to
seasonable values, in the mid 50s to low 60s, followed by above
normal temps Fri into the weekend. Temps are still expected to
reach the 70s on Sat (75-90% chance), which could approach record
territory in some spots.

One minor change to the forecast was the introduction of low
chance (15-20%) precip south of I-70 late Thurs night/early Fri
AM. This is in response to LLJ forcing. If this precip does
develop, it`s unlikely to amount to more than a few hundredths of
rain.

A better chance of rain still appears possible this weekend or
early next week, as a deep trough over the western US starts to
emerge onto the Plains. Forecast confidence remains quite low with
this system. Yesterday, models depicted a split flow pattern with
a phased wave ejection, but now models depict the southern wave
cutting off over the desert SW and taking much longer to reach our
region. The latest NBM is dry through the day on Sat, with PoPs
slowly increasing overnight and reaching the 30-40% chance range
for Sun-Mon. I`d expect the PoP timing to narrow and values to
increase as the system comes into better focus. The probability of
total rainfall amounts of 1" is 10-30% through Tuesday morning
(highest south of I-70). It is too early to meaningfully assess
the severe storm potential due to the significant model
differences in this system`s evolution.

Erwin

&&

.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 521 AM CST Tue Nov 11 2025

VFR conditions are expected through the period. The main concern
this period is breezy southwesterly winds, which could gust up to
30 knots between mid-morning and sunset. In the evening, a low-
level jet develops over KDEC/KCMI, resulting in a few hours of
marginal LLWS conditions (2000 ft winds of 40-45 knots). Winds
turn to westerly overnight. Broken high clouds are expected this
morning, giving way to clearing skies this afternoon into the
evening.

Erwin

&&

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

$$