808
FXUS63 KILX 291756
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1156 AM CST Sat Nov 29 2025

.KEY MESSAGES...

- An early season winter storm system will create significant
  travel difficulties across much of the Midwest this weekend.

- Snow will be the primary precipitation type today...before
  mixing with rain along/south of I-70 by this evening.

- Snow accumulations will range from 1 to 3 inches south of
  I-70...to as much as 9 to 12 inches along and north of a Macomb
  to Bloomington line.

&&

.UPDATE...
Issued at 1028 AM CST Sat Nov 29 2025

16z/10am radar imagery and area observations indicate that snow
has spread across nearly the entire KILX CWA...except for the far
SE around Olney and Lawrenceville. Early reports from where the
snow has been falling the longest generally show accumulations of
2-5 inches along/south of a Peoria to Decatur line...with as much
as 5-7 inches already on the ground across portions of Sangamon
and Morgan counties. Current obs show above freezing temps and a
rain/snow mix in the Saint Louis metro, but it will take several
hours for these warmer readings to arrive in central Illinois due
to a continued easterly component to the wind. As a result, snow
will continue to fall across the entire area through early afternoon
before gradually mixing with rain along/south of a Rushville...to
Taylorville...to Robinson line after 21z/3pm. In addition to the
falling snow, SE winds gusting 25-35mph will create areas of
blowing/drifting throughout the day. The precipitation is expected
to rapidly taper off from southwest to northeast across the area
this evening as low pressure tracks into north-central Illinois.
At the same time, surface temperatures will climb above freezing
everywhere...except perhaps northwest of the Illinois River around
Galesburg. This will allow any lingering light precip to mix with
rain before coming to an end. It will also aid in melting some of
the snow on area roadways. Storm total snowfall is still expected
to range from 6-10 inches across a good chunk of central
Illinois...with lesser amounts of 2-3 inches along I-70. Further
south, am becoming concerned that Richland and Lawrence counties
may receive only trace amounts due to the lack of ongoing precip
in those counties and the expected warm-up late this afternoon.

Barnes

&&

.DISCUSSION...
Issued at 356 AM CST Sat Nov 29 2025

Satellite imagery early this morning shows a mid-level trough
digging across the Plains, accompanied by a deepening plume of
moisture surging northward up the Mississippi Valley. The surface
low pressure, currently centered over west-central Kansas, is
forecast to lift toward northern Illinois tonight as the
associated mid-level wave pivots across the central United States.
Radar exhibits a broad swath of precipitation wrapping around
this system, with its eastern edge just beginning to enter west-
central Illinois as of 2 AM CST.

While the 00Z sounding from last night indicated a significant
layer of dry air below 700 mb, this layer has now eroded. Regional
surface observations confirm strong warm and moist advection
developing north of the surface low, with upper-jet diffluence
contributing to an expanding area of precipitation.

Snow has been the initial precipitation type, and it is expected
to remain the dominant type through the afternoon. This is due to
the thermal profile and surface wet-bulb temperature remaining
cold enough. A notable trend across the last few model cycles is a
less aggressive push of warm air into the I-72 corridor by late
afternoon. Consequently, the potential for a rain-snow mix
(partial melting through a saturated layer) has been shunted
further south, closer to the I-70 corridor. This shift means most
of central Illinois is now likely to experience a long-duration,
all-snow event throughout the afternoon hours.

No changes were made to our winter storm headlines overnight, and
forecast snow totals largely remain intact from yesterday`s
forecast. If anything, our confidence in forecasting warning-
criteria snow across east-central Illinois has increased. We
continue to support a broad swath of 5-8 inches of snow in areas
north of I-70, with the potential for 9-12 inches in areas near
and north of a Macomb-to-Bloomington line. At this point, the
greatest uncertainty lies in areas near and south of I-70 where
there will likely be sharp cut-off in accumulating snow, owing to
the potential for a rain-snow mixture by late afternoon. In such
areas, we have maintained between a trace and 4 inches of snow.

Gusty southeast winds today will shift to the west tonight as the
surface low lifts across the forecast area. Accumulating snow,
combined with wind gusts of 25-35 mph, increases the risk of
blowing and drifting snow, occasional whiteout conditions, and
sporadic power outages.

Precipitation is expected to decrease to flurries or drizzle from
west to east after approximately 6 PM this evening as the system
dry slot moves across central Illinois. Overnight, additional snow
showers are possible near and north of I-74 where wrap-around
moisture re-enters the area, though additional snow accumulation
is unlikely to exceed one inch.

After today, we will enter a prolonged period of unseasonably
cold weather. It won`t necessarily be worthy of a Cold Weather
Advisory on any given day, but there is a legitimate chance that
temperatures do not warm above freezing at all next week as strong
surface high pressure builds in and out of the central U.S. At
this time, the coldest period appears to be Wednesday night and
Thursday night when wind chill values could fall below zero.

Aside from the cold weather impacts, we continue to monitor the
potential for a quick-hitting burst of snow Monday night as a pair
of jet streaks phase together over the region ahead of a digging
trough. At this point, much of the ensemble guidance supports at
least a few inches of snow beneath the jet streak. Fortunately,
p-type will not be a concern with this event. We will be plenty
cold, and with SLRs closer to 12-15:1.

MJA

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1156 AM CST Sat Nov 29 2025

1730z/1130am radar shows a band of heavy snow lifting northward
toward the I-74 corridor. Visbys beneath the band have been
reduced to 1/4 to 1/2 mile...and am expecting these conditions to
spread into KPIA/KBMI/KCMI over the next hour or so. Based on the
latest radar trends and HRRR/RAP output, have ended the heaviest
snow and raised vibsys back up to 1 mile at KSPI by 22z...then
further northeast to KBMI/KCMI by 00z. The snow will likely end as
a light rain/snow mix at the I-72 terminals...with dry conditions
returning across the board after the 03z-05z time frame. IFR
ceilings will persist during the snowfall, with ceilings climbing
to MVFR overnight into Sunday morning. Winds will initially be SE
with gusts of 25-30kt this afternoon...then will become S/SW and
decrease slightly this evening. Once low pressure lifts into the
Great Lakes and pulls a cold front through the region, winds will
veer to NW and once again gust 25-30kt from around midnight
through Sunday morning.

Barnes

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM CST Sunday for ILZ027>031-
036>038-040>057-061.

Winter Weather Advisory until 6 AM CST Sunday for ILZ062-063-
066>068-071>073.

&&

$$