965
FXUS63 KILX 221551
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
951 AM CST Fri Nov 22 2024

.KEY MESSAGES...

- Low clouds and patchy drizzle may result in some impacts to
  general aviation, especially across eastern IL, but otherwise
  the pattern for today is more tame and less raw.

- Warmer and breezier conditions return this weekend ahead of some
  light rain.

- Trending much colder by the middle of next week with some
  middling probabilities (40-60% chance) for wintry precipitation
  during the Wed - Fri timeframe that could result in slippery
  conditions.

&&

.UPDATE...
Issued at 951 AM CST Fri Nov 22 2024

The upper low that brought wintry precipitation to the area
yesterday is centered over the Northeast US with cyclonic flow
positioned over the area on the western fringes of it. Widespread
cloud cover blankets the Midwest states, with similar conditions
expected to continue through at least the first half of Saturday as
low-level moisture remains trapped underneath an inversion. Some
periodic drizzle could be seen, mainly in eastern parts of the
state, where some subtle lift in the 950-800 mb layer overlaps the
low-level moisture. Breezy and cool conditions will be seen today
with northwest winds gusting between 20-25 mph.

NMA

&&

.DISCUSSION...
Issued at 130 AM CST Fri Nov 22 2024

Early morning GOES-16 water vapor imagery depicts a highly
amplified pattern over the Lower 48, with a strong upper-level low
centered over the Mid-Atlantic region and a ridge axis nosing
across the Upper Midwest.  Model guidance remains in excellent
agreement that this pattern will continue to amplify today as a
pair of additional upper-level disturbances emerge across the
Canadian Prairies and Pacific Northwest.

More locally, we will remain cloudy through tonight as shallow
moisture becomes trapped beneath a subsidence inversion and deep
cyclonic flow. Mesoscale soundings even support a little bit of
drizzle today, mainly east of Interstate 55, where there appears
to be just enough low-level lift through a saturated 0-1.5 km
layer. Precip could even become showery at times this afternoon as
steepening low-level lapse rates introduce weak/shallow
instability, but that`s neither here nor there. On the whole,
today will be less windy and less cold, with any impacts likely
confined to general aviation.

For tonight, low clouds will likely hang around. It`s not until
Saturday afternoon, once low- level winds become southwesterly,
that clouds may ultimately lift and break. As a hedge, we have
bumped temperatures up a degree or two tonight to account for the
abundant cloud cover.

A warming trend will peak by Sunday, with afternoon highs surging
near 60 degF within an aggressive warm advection regime and ahead
of a sharpening baroclinic zone. There is currently a medium
(40-60%) chance for light rain ahead of the cold front, with
blended guidance suggesting between a Tr-0.25" in areas east of
Interstate 55. Temperatures then whipsaw colder by Monday night
as a shortwave trough digs across the Corn Belt and pushes the
cold front through central Illinois. With the influx of gusty
winds and colder temperatures, we could see wind chill values
bottom out in the teens by Tuesday morning.

Attention then turns to the middle of next week. It being the
holiday and travel volume picking up, we are especially sensitive
to potential weather impacts. Current model trends show an area of
surface low pressure lifting across the Lower-Mississippi Valley
and toward the Ohio River Valley. At this point in time, guidance
appears to be split among two camps. The first camp is the
GFS/GEFS, which offers a lower-amplitude wave lifting across the
lower-Mississippi, resulting in less model QPE across central and
southeast Illinois. The second camp is the ECMWF/CME and its
suite of ensemble guidance, which exhibits a higher-amplitude
wave; a stronger/more-organized surface low; and higher model QPE.
If model guidance trends more towards the second camp, we will
become more concerned for wintry precip and associated travel
impacts during the Wed-Fri timeframe. Currently, blended (NBM)
guidance sports a 40-60% chance for precipitation over this
period, but largely mutes the snow/ice signal. The raw ensemble
(LREF) data, on the other hand, shows a more robust snowfall
signal, with the 10-90th percentile goal posts offering anywhere
between Tr-4" in areas north of I-70. The best thing to do at
this time is to not anchor to any one model solution, and to
continue monitoring trends through the weekend.

MJA

&&

.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 503 AM CST Fri Nov 22 2024

Low-level moisture will remain trapped beneath a subsidence
inversion today and tonight. The net result will be continued
low/MVFR clouds through this TAF period. There could be occasional
bouts of IFR cigs this morning and through midday, primarily at
CMI & BMI where patchy drizzle comes and goes. Otherwise, the TAFs
may be too pessimistic at PIA & SPI for later tonight, with some
models suggesting a return to VFR cigs at these sites as early as
03z. However, think this may be premature with light winds
remaining from the WNW tonight. Instead, thinking low clouds will
linger into Saturday morning before lifting and breaking as winds
back southwest.

MJA

&&

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

$$