107
FXUS63 KILX 222313
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
513 PM CST Fri Nov 22 2024

.KEY MESSAGES...

- Overcast skies will stick around through at least the first half
  of Saturday before we start to erode the low stratus later in
  the day.

- Warmer and breezier conditions make an appearance on Sunday
  before a frontal system brings our next shot of light rain
  (30-50% chance) Sunday night into Monday.

- Sharply colder weather returns by the middle of next week with
  another frontal system potentially bringing wintry precipitation
  Wednesday into Thursday night (low confidence).

&&

.DISCUSSION...
Issued at 221 PM CST Fri Nov 22 2024

A large upper low is centered over the Northeast US this afternoon,
with mid-level ridging nosing into the Midwest states. Broad
cyclonic flow on the western fringes of the upper low has kept skies
overcast and brought periods of drizzle to eastern IL today where
subtle lift overlaps the moisture layer. The pesky low stratus will
be slow to depart with forecast soundings showing low-level moisture
remaining trapped beneath an inversion through at least tonight, if
not through the better half of Saturday. Surface ridging slides
southeast into the area Saturday morning, which should work to erode
the low stratus from west to east as low-level flow becomes
southwesterly. Confidence remains low on how quickly this will
occur, but leaned more pessimistic and increased sky cover through
much of Saturday morning across the area. In addition to this,
brought lows up by several degrees tonight and down a few degrees on
Saturday due to the increased cloud cover. Temperatures should
bottom out in the middle to upper 30s tonight with highs in the mid
to upper 40s on Saturday.

Warmer and breezy conditions will be seen Sunday as southerly flow
ramps up ahead of a developing system to our west. A surface low
will begin to approach by Sunday evening, sending a warm front
through the area. Precipitation chances increase Sunday night into
Monday as the system`s cold front slides through the area.
Precipitation amounts will be minimal, with totals generally
under 0.10".

Much colder temperatures filter in behind the front for the middle
to end of next week as a series of upper troughs send much lower mid-
level heights southward into the Midwest states. The Climate
Prediction Center favors a 60-80% chance of below normal
temperatures through the end of the month.

Another chance for precipitation is introduced Wednesday into
Thursday night. The track of the low looks to work through the Ohio
Valley or south of there, which would place us on the cool side of
the system and favor wintry precipitation. The ECMWF Shift of Tails
(SoT) for snow shows a contour of 1 over central Illinois for this
period with low values on the the Extreme Forecast Index (EFI). So
this essentially means there is high uncertainty with a few ensemble
members indicating an extreme event with respect to climatology.
With that said, the last few runs of the deterministic GFS have
shifted the low track further south, with the 22.12Z run making a
big jump south and removing all QPF from our area. This differs from
the ECMWF and CMC where QPF is still splattered over the area in
what would be the low`s deformation zone. There is still alot of
uncertainty with this, but all eyes will remain on this period as it
could potentially impact a very busy travel time with the
Thanksgiving holiday.

NMA

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 512 PM CST Fri Nov 22 2024

MVFR ceilings blanket the region, with a back edge over central
IA/MO. We expect ceilings to gradually lower this evening,
reaching IFR levels overnight. A clearing trend should occur
around midday Saturday, as low level winds back to the southwest.
Winds to be much lighter than the past few days, near/under 10 kt.

25

&&

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

$$