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000
FXUS63 KILX 240150
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
850 PM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Temperatures will fall into the 30s Thursday morning. There is a
  around a 50-80 percent chance along and north of I-74 for temps
  to fall to 37 or below with frost formation a possibility.

- A warm front will lift north across central Illinois Friday
  ushering in much warmer temperatures with highs near 80F over
  the weekend. There will also be periodic chances for showers and
  storms Friday through Sunday, some of which may be severe.

&&

.UPDATE...
Issued at 850 PM CDT Tue Apr 23 2024

A cold front continues to edge southeastward this evening...with
01z/8pm obs showing it along the Illinois River. The front will be
accompanied by little more than a few mid-level clouds and a shift
in the wind over the next few hours. Based on the latest RAP/HRRR,
it will cross I-55 by midnight...then exit the KILX CWA into Indiana
overnight. Low temperatures will drop into the lower to middle 40s.

Barnes

&&

.DISCUSSION...
Issued at 237 PM CDT Tue Apr 23 2024

Today and Tonight...
This afternoon, a diffuse cold front stretches from central
Wisconsin into northeastern Missouri. A prefrontal band of
showers and a few storms in the warm advection continues across
central Illinois, but will gradually taper off from the north,
ending north of I-72 around 22Z/5pm CDT and north of I-70 around
01Z/8pm CDT. Meanwhile, the aforementioned cold front will push
through the area through the evening with southwest winds veering
to the northwest and eventually northeast in its wake. Meanwhile,
the latest RAP continues to advertise a narrow ribbon of around
200 J/kg MLCAPE along the front, but weak frontal convergence and
displacement from the upper wave digging into the Great Lakes will
result in little if any development across most of central
Illinois. The best chance for an isolated shower or storm will be
along and north of the I-74 corridor. Temperatures are expected to
fall into the lower to mid 40s overnight.

Wednesday and Thursday...
High pressure will build across the Great Lakes midweek resulting
in northeast to east winds across central Illinois with below
normal temps Wednesday to near normal temps Thursday. Temps will
bottom out Thursday morning with lows in the mid 30s to lower
40s, coldest along the I-74 corridor. There is some potential near
and north I-74 for frost development as temps approach the
freezing mark, but a modest breeze will be a mitigating factor.
There is a small (20-40 percent per NBM) chance for temps to fall
below freezing along the I-74 corridor.

Friday through the weekend...
Two separate areas of low pressure will lift from the central
Great Plains to the upper Great Lakes Friday though Sunday. A
broad corridor of southwesterly flow and a favorable fetch off of
the Gulf of Mexico will be in place ahead of the low across the
Midwest. This will result in a surge in temps and humidity
starting Friday and temps will peak with highs near 80F over the
weekend and dew points rising well into the 60s. This more summer-
like heat and humidity coupled with strong spring kinematics will
set the stage for at least a couple rounds of severe weather
during this time frame.

The first low is set to lift across northeastern NE/northwestern
IA Friday evening. Instability will be strongest across IA/MO
but will bleed into western Illinois. Storms should ramp up to our
west as the low level jet strengthens Friday evening with storms
riding the instability gradient east into Illinois. The severe
threat may extend into portions of west central Illinois Friday
night but should diminish with eastward extent and time as storms
outrun stronger instability and the LLJ veers/weakens.

Shortwave ridging moving overhead Saturday should result in a lull
in precip chances during the day, but temps warming to near 80
degrees alongside dew points into the lower to mid 60s will
contribute to moderately strong instability (MLCAPE 1500-2000
J/kg) Saturday afternoon and evening. Moderate flow aloft will
result in 35-40kt deep layer shear. Forcing appears weak/nebulous
Saturday, but so does CINh by mid afternoon, so isolated to widely
scattered thunderstorms could be possible with shear/instability
parameter space favorable for any storms to be severe.

Sunday`s low will take a slightly more easterly track compared to
the Friday low, with the attendant severe weather threat likewise
shifting east further into Illinois. There remains some
uncertainty on the amount of instability owing to ongoing
convection and cloud cover in the region. Timing of cold frontal
passage also appears to be late at night which will limit
instability along the front. If we are able to realize some
stronger instability, deep layer shear and forcing all appear
favorable for a severe weather threat to once again materialize.

Deubelbeiss

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 637 PM CDT Tue Apr 23 2024

Skies have cleared at the central Illinois terminals early this
evening: however, a cold front currently approaching the Illinois
River will produce SCT mid-level clouds and a shift in the wind
later. Based on current trends and HRRR/RAP forecast, have veered
winds to NW at KPIA by 03z...then further southeast to KDEC/KCMI
by around 05z. Winds immediately behind the front have gusted
25-30kt across Iowa/far western Illinois through the afternoon.
Once the sun sets and the atmosphere decouples, the gusts will
decrease, but am still expecting a few gusts of 15-20kt along/west
of I-55 after FROPA. After a couple hours of gustiness, winds
will decrease and veer to the NE late tonight into Wednesday.
Despite FROPA, skies will not become completely clear tonight as
SCT mid-level clouds across Minnesota/Wisconsin drift southward
into central Illinois through Wednesday.

Barnes

&&

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

$$