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000
FXUS63 KILX 250521
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1221 AM CDT Thu Apr 25 2024

.KEY MESSAGES...

- Temperatures will fall into the 30s across most of central
  Illinois tonight. There is a 60-80 percent chance of sub-
  freezing temps from Lacon to Bloomington Rantoul and areas
  north.

- There will be periodic chances for showers and thunderstorms
  Friday through Sunday. Some storms could be severe (5-15
  percent) at times and there is potential (5-15 percent) for
  locally heavy rain.

&&

.DISCUSSION...
Issued at 226 PM CDT Wed Apr 24 2024

Through Thursday...
High pressure will slowly drift east across the Great Lakes in
the near term resulting in continued cooler but otherwise quiet
weather conditions across central Illinois in the near term. Some
cold air stratocu persists across much of central Illinois this
afternoon, but should continue to gradually erode from the edges
with mainly portions of east central Illinois holding onto cloud
cover late into the evening. Temperatures will fall into the 30s
across most of central Illinois overnight into Thursday morning.
While there remains some concern that a light easterly gradient or
lingering clouds may mitigate frost potential tonight, have
enough confidence in temps near the freezing mark to hoist a Frost
Advisory for portions of the I-74 corridor Thursday morning.

Friday through the weekend...
A pair of low pressure systems are progged to lift from the
central Great Plains into the Upper Midwest; the first Friday into
Saturday, and the second Saturday night through Sunday night. Low
level trajectories off of the Gulf of Mexico will allow dew
points to rise into the 60s as the first warm front lifts across
central Illinois Friday. Dew points further rise into the mid 60s
this weekend accompanied by high temperatures near 80 degrees.

Increasing cloud cover is expected Friday along with scattered
showers and non-severe storms as mid level warm air advection
overspreads central Illinois. This will result in only modest
diurnal destabilization Friday afternoon with the strongest
instability progged to set up well to our west along the KS/MO
state line. Storm coverage should increase to our west Friday
evening as a low level jet strengthens. Storms will spread east
overnight and could bring an accompanying severe weather threat as
instability advects into Illinois overnight associated with a
veering LLJ. Eastward extent of the severe weather threat remains
uncertain but could reach portions of central Illinois.

As the first low lifts into the Upper Midwest Saturday, a broad
warm sector will in in place across portions of the Mid
Mississippi Valley. Forecast soundings show steep low/mid level
lapse rates and minimal capping in place Saturday afternoon.
Forcing will be a bit nebulous, but shouldn`t take much to kick
off deep convection. LREF joint probabilities of CAPE >500 J/kg,
Cin >-25 J/kg, and deep layer shear >30kt are maximized across
central Illinois west of I-55 Friday afternoon around 50 percent.
If storms are able to initiate, this appears to be the time frame
for highest impacts from severe storms during the Friday-Sunday
time frame.

Second low begins to take shape Saturday night into Sunday over
the Great Plains and will take a similar path as the first low,
albeit ever so slightly further east. Similar to the first low,
LLJ appears to be focused to our northwest Saturday night, and
the strongest instability is also in place to our west lending
some uncertainty in whether the severe threat will make it as far
east as central Illinois. The trailing cold front will eventually
sweep across central Illinois Sunday night into Monday morning
marking the back edge of the precip chances.

All said through the weekend, mean 72-hr QPF amounts through
Monday morning look to total between 1 and 2 inches for most of
central Illinois with highest amounts in the west. 90th percentile
amounts peak between 3-4 inches west of the Illinois River and
would not be suprised to see some localized swaths of these higher
end amounts.

Deubelbeiss

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1221 AM CDT Thu Apr 25 2024

VFR conditions will be observed through the TAF period. Light east
winds overnight will veer to the southeast Thursday morning with
speeds around 10 kts.

NMA

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 6 AM CDT early this morning for ILZ030-031-
038-043>046.

&&

$$