158
FXUS63 KILX 150900
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
300 AM CST Wed Jan 15 2025

.KEY MESSAGES...

- Wind chill values this morning will generally range between zero
  and ten below zero. Prolonged exposure to these conditions could
  result in frostbite in as little as 30 minutes.

- A brief warm-up will close out the week before another push of
  very cold temperatures arrives over the weekend. Confidence is
  currently high (70% chance or greater) that wind chill values
  will be colder than 10 below zero Sunday Night and Monday night.

- Patchy freezing fog is a possibility Thursday night, though
  forecast confidence is currently lower than 50%.

- Light rain is likely (70% chance or greater) Friday evening in
  areas east of I-55, briefly mixing with light snow by Saturday
  morning. The probability for accumulating snow is very low.

&&

.DISCUSSION...(through next Wednesday)
Issued at 1257 AM CST Wed Jan 15 2025

Modified surface high pressure continues building across central
Illinois this morning ahead of a low-level ridge axis. Strong
radiational cooling beneath a residual snowpack has resulted in
very cold temperatures this morning, generally near zero, give or
take a few degrees. Light wind or no wind has largely mitigated
the wind chill effect, but there are a couple ASOS/AWOS sites
reading wind chill values as low as ten below zero.

A weak cold front will push into the region tonight as strong
shortwave energy digs into the Great Lakes region. This feature
could allow for a brief period of warm-advection snow or flurries
in areas north of a Galesburg to Terre Haute line, but forecast
confidence is very low given how disjointed column moisture (RH)
appears in model soundings.

Temperatures will surge into the 30s on Thursday as the effects
of compressional warming advect into the Midwest from the Plains.
The warming trend then continues into Friday as gusty southerly
flow moves in ahead of a frontal system, providing temperatures in
the 40s.

Some concern for shallow dense fog remains Thursday night as much
warmer low- level air begins to advect overtop a diminishing
snowpack. A quick glance at T/Td spreads from the NBM suggests
that the real honest push of warm advection has been delayed until
Friday afternoon, with sfc temps still in the mid-to-upper 20s
Thursday night. This would suggest that any fog that might develop
during this timeframe would be freezing fog. Overall, forecast
confidence in fog development remains at less than 50%, but there
is some signal among model soundings (GFS, SREF, NAM3km) for it.
We have made mention of patchy freezing fog in our gridded
forecast, but will refrain from messaging it until confidence
increases.

Light precip will spread into Illinois by Friday evening as the
winter of phased waves over the central U.S. continues. Forecast
guidance remains in excellent agreement that low-level
temperatures will become warm enough to support rain in areas east
of the Illinois River Valley, at least at onset. It then becomes a
race between when the low-level moisture departs versus when the
cold temperatures spill into the region. For now, the majority of
ensemble guidance supports at least a brief change over to snow,
but with a very low probability (< 30% chance) for accumulating
snow.

The return of very cold temperatures is likely by Sunday night as
cross-polar flow disburses another lobe of arctic air to the
central U.S. There is currently a high confidence (70% chance or
greater) in wind chill values colder than ten below zero both
Sunday night and Monday night. Temperatures then look to moderate
a little warmer by Wednesday, but the consensus around here is
that we will remain in the tank through late January before we get
a bona fide thaw by early February.

MJA

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1126 PM CST Tue Jan 14 2025

VFR conditions continue the next 24 hours, with generally some mid
clouds increasing by evening. Light/variable winds become
southwest Wednesday morning, then increase to near 10 knots by
midday. Some concern with potential for LLWS toward the end of the
period near KPIA/KSPI, though confidence levels are not enough to
mention at this time.

Geelhart

&&

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

$$