224
FXUS63 KILX 101127
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
527 AM CST Fri Jan 10 2025

.KEY MESSAGES...

- Accumulating snow will spread from west to east today and may
  affect the morning and/or evening commute. Confidence is high in
  1-3 inches generally along and north of I-72, with 2-4 inches
  south of there.

- Another round of flurries and freezing drizzle may provide
  limited winter weather impacts on Sunday.

- Reinvigorating shot of cold air returns by the middle of next
  week with nighttime wind chill values bottoming out Tuesday and
  Wednesday. There is currently a high confidence (70% or higher)
  for below zero wind chill values each of those nights.

&&

.DISCUSSION...
Issued at 128 AM CST Fri Jan 10 2025

Early morning water vapor imagery depicts two prominent mid-level
shortwaves, one digging into northern ND/MN and another lifting
across west Texas. These features have phased together, producing
a weak cold front that extents from northern Wisconsin to the
Texas Caprock, as evident by a narrow plume of moisture. Ahead of
the diffuse cold front lies a much deeper and broader area of
subtropical moisture that is spreading northward across the lower-
and mid-Mississippi Valley where the phasing of the upper-level
jet cores is providing an abundance of upper-level divergence and
synoptic ascent.

As of 3am, radar trends and upstream obs across the Missouri
Ozarks confirm the onset of light snow, and it should not be long
before the snow commences across all of central and southeast
Illinois with sfc dewpoint depressions now less than 3 degF. Short
term model guidance remains in excellent agreement with its QPF
output through tonight, ranging between 0.1"-0.3" and focusing
the higher amounts down along I-70. When assuming a 12:1 SLR, we
get a snowfall forecast of 1-4" across our forecast area.

There is some bust potential along and west of the Illinois River
Valley where snow will shutoff relatively quickly this afternoon
once the cold front passes through and drier air & subsidence
work in. East of this tight gradient, the abundance of synoptic
moisture/ascent will lead to several hours of light and steady
snowfall. While the probability of 1"/hr snowfall rates are very
low throughout this event (< 10% chance), 0.2"-0.5"/hr rates
during the morning and/or evening commute may lead to minor
travel impacts.

Accumulating snow will end from west to east by evening, but we do
maintain a chance of flurries through tonight as steepening lapse
rates and just enough moisture and lift in the lowest 5 kft help
poke into a very shallow DGZ.

After a lull on Saturday, light wintry weather looks to return by
Sunday as weak clipper system pushes across the Upper Midwest and
into the Great Lakes region. A quick glance at the thermal profile
suggests we may be dealing with occasional flurries or freezing
drizzle. While the flurries would be rather fleeting, the freezing
drizzle could cause some limited impacts and is something we will
continue to monitor.

Beyond this weekend, conditions look dry and cold as temperatures
once again plummet behind Sunday`s clipper. Daytime highs,
courtesy of the deterministic NBM, are forecast to be in the
teens between Monday- Wednesday with overnight lows in the single
digits. This seems reasonable given a fresh snowpack and modified
Canadian high pressure building across the area. Even with light
winds, wind chill values will be below zero during the midweek
period. Then, after a brief period of moderating temperatures to
close next week, another shot of cold air looks poised to return
for the following week.

MJA

&&

.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 526 AM CST Fri Jan 10 2025

Light to moderate snow is overspreading central Illinois this
morning and is expected to be heaviest across portions of east
central/southeast Illinois including DEC/CMI late this morning
into the afternoon. Ceilings are expected to build down to IFR.
Visibility will fall to 1/2SM in the east but should remain
slightly higher to the west. A cold front will sweep across
central Illinois late this afternoon and evening turning winds
northwest in its wake and ending the accumulating snow...though a
few scattered flurries will remain possible through tonight.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST this evening for ILZ029-
031-036>038-040>043-047>053.

Winter Weather Advisory until midnight CST tonight for
ILZ044>046-054>057-061>063-066>068-071>073.

&&

$$