270
FXUS63 KILX 272302
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
502 PM CST Thu Nov 27 2025

.KEY MESSAGES...

- An early season winter storm system will create travel
  difficulties across much of the Midwest during the upcoming
  holiday weekend.

- Snow will be the primary precipitation type late Friday night
  into Saturday morning...before mixing with rain along/south of
  I-70 by Saturday afternoon and evening.

- Significant snow accumulations in excess of 5 inches are likely
  along and north of I-70 on Saturday.

&&

.SHORT TERM... (Tonight through Friday)
Issued at 240 PM CST Thu Nov 27 2025

A sprawling ridge of high pressure extending from Saskatchewan
southeastward into the Southern Plains will dominate the weather
across central Illinois over the next 24 hours. As the ridge
nears, the pressure gradient will relax...and the persistent
strong winds that have plagued central Illinois for the past
couple of days will ease. NW winds will drop to 10mph or less
tonight, then will become light and variable on Friday as the high
drifts overhead. Much below normal temperatures will
continue...with lows tonight dipping into the upper teens and
lower 20s and highs on Friday only reaching the lower to middle
30s.

Barnes

.LONG TERM... (Saturday through Next Thursday)
Issued at 240 PM CST Thu Nov 27 2025

A vigorous short-wave trough evident on 19z/1pm water vapor
imagery over the Pacific Northwest will cross the Rockies and
amplify during the day Friday...resulting in surface cyclogenesis
in the lee of the Rockies across eastern Colorado. The low will
then track northeastward from Kansas Saturday morning to southern
Michigan by Sunday morning. With ample cold air initially in
place, the stage will be set for snow across central Illinois
beginning late Friday night and lasting through much of the day
Saturday. 12z CAMs are generally in good agreement on the initial
start time for the snow after midnight...with only the HRRR
suggesting an initial surge of very light WAA snow perhaps during
the evening. Given the very dry boundary layer environment, think
this may be a bit too aggressive. As a result, have limited
evening PoPs to just 20-30% along/west of the Illinois River. As
the low approaches and the profile moistens from the top-down,
snow will develop/spread eastward overnight, with general consensus
pushing it as far east as I-57 by 12z Sat. The 12z HREF mean
snowfall through 12z Sat is around 1 inch along I-55 and 2-3
inches along/west of the Illinois River.

Low pressure will reach northern Missouri by 18z Sat...with
strong/saturated isentropic lift on the 295K and 300K surfaces
ensuring widespread moderate to heavy snow across the area through
midday. After that, a surge of warmer air ahead of the low will
try to push into parts of central/southeast Illinois during the
afternoon and evening. The exact northward reach of the warm nose
is still somewhat in question...and will be better resolved as
CAMs begin to cover the full time-range of the storm system over
the next couple of model cycles. At this time, think snow will
remain the primary precip type north of I-70...with the snow
mixing with rain along/south of I-70 during the afternoon.

As the low lifts into north-central Illinois, deep-layer moisture
will be shunted eastward and the steadiest/heaviest precip will
quickly dissipate from west to east by Saturday evening. Am still
expecting light snow or a light snow/rain mix to linger through
the evening and into the overnight hours: however, the significant
accumulation will be over by that time. The NAM Garcia Method
shows average 12-hour mixing ratios of 3-3.5g/kg across the
northern half of the KILX CWA...with 3.5-4g/kg across the south.
This would roughly translate to 5-8 inches of snow. However exact
snow totals will be dependent upon where the precip remains all
snow and where it mixes with rain. Based on the latest data, am
most confident that the northern CWA along/north of a Macomb to
Bloomington line will stay all snow throughout the entire event.
The latest Probabilistic Winter Storm Severity Index (PWSSI) backs
this up...indicating a 20-30% chance for Major Impacts across
this area. As a result, think a wide swath of central Illinois
north of I-70 will see 5-8 inches of snow...with 8 or more inches
along/north of a Macomb to Bloomington line. Given these expectations,
the current Winter Storm Watch area looks reasonable and will not
be altered at this time.

On a side note: this will be a heavy/wet snow that will be
difficult to shovel. While S/SE surface winds will gust to around
25mph with the snow, think blowing/drifting will be at least
partially mitigated by the wet nature of the snow. Travel is
highly discouraged on Saturday...especially from central Illinois
northward into the Great Lakes.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 502 PM CST Thu Nov 27 2025

A band of MVFR ceilings was sinking south of the I-80 corridor
late this afternoon. As winds in the cloud bearing layer weaken
this evening, short range models show the leading edge of the
clouds slowing, then stalling near the I-74 corridor over the next
few hours. This makes for a tricky forecast for KPIA-KBMI-KCMI,
with the added complication of the south side of the cloud deck
just above the MVFR threshold. For now have tempoed in a few hour
period of SCT025 BKN035 for the terminals near I-74 and will
amend as necessary. Otherwise, VFR skies through the period with
west- northwest winds near to under 10 kt.

25

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late Friday night through late Saturday
night for ILZ027>031-036>038-040>057-061>063-066.

&&

$$