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000
FXUS63 KILX 230836
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
336 AM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Rain chances increase shortly after daybreak and continue
  through early evening. Scattered thunderstorms could accompany
  the rain, with a few stronger storms possible north of I-74
  later this afternoon.

- Frost/freeze potential returns near and north of Macomb to
  Mattoon line Thursday morning. There is a 40-80% chance for air
  temperatures below 37 degrees.

- A warmer and more active weather pattern arrives late in the
  week. Several chances for showers and storms exist late Thursday
  night through the weekend, including the potential for heavy
  rain and severe weather.

&&

.DISCUSSION...
Issued at 336 AM CDT Tue Apr 23 2024

Radar imagery early this morning shows spotty showers over parts of
the state. Most of this is struggling to reach the ground due to dry
low to mid-level air. Forecast soundings show a wing of moisture
associated with a mid-level shortwave advecting into the area
shortly after daybreak, which is when we should start to see more
precipitation reaching the ground. Showers and isolated storms will
persist through this afternoon, gradually shifting southeast through
this evening. High resolution convective allowing models have shown
a secondary line of widely scattered showers and storms developing
just ahead of a southeastward progressing cold front later this
afternoon into early evening north of I-72. Instability will be
minimal due to the overall lack of moisture, but favorable wind
shear and steep low to mid-level lapse rates could support a few
storms capable of gusty winds and small hail. QPF through tonight
looks to range from 0.25 to 0.50 inches.

Surface ridging spills into the area for the middle of the week,
turning temperatures cooler. Overnight lows Wednesday night into
Thursday morning will dip down into the middle 30s to low 40s,
posing a threat for frost. The highest chances for frost development
will be near and north of a Macomb to Mattoon line where the NBM has
a 40-80% chance for temperatures being 37 degrees or colder.

The cool snap will be short lived with upper ridging bringing warmer
temperatures back into the area by the end of the week. Temperatures
will gradually warm through the weekend, approaching 80 degrees in
spots by Saturday. A series of upper impulses will bring an extended
period of active weather Friday through the weekend characterized by
storms, heavy rain, and some severe weather. The first shot arrives
late Thursday night into Friday morning as a surface low lifting
into the northern Plains sends a warm front north through the area.
Storm chances continue into Friday, though higher instability looks
to remain focused just west of our CWA. Despite this, strong
effective wind shear due to an approaching mid-level jet may support
a few organized storms Friday afternoon/evening as activity spreads
east.

Better instability shifts into the area on Saturday as a cold front
stalls out somewhere just west of here. Storm chances will increase
once again Saturday evening as an upper trough lifts toward the
middle Mississippi Valley, potentially bringing another shot at
some severe storms. A deepening surface low will lift toward the
Great Lakes Region on Sunday, sending a cold front through the
area Sunday night. Timing differences still remain with this
feature, but favorable parameters once again could support severe
weather if the timing of FROPA isn`t too late. 72 hour QPF totals
between Friday and Monday look to be rather hefty with the NBM
indicating a 50-80% chance of 1.5 inches or more and a 20-50%
chance of 2 inches or more (higher end chances west of I-55).

NMA

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1146 PM CDT Mon Apr 22 2024

Latest CAMs continue to spread showers into KPIA by 11z...then
further southeast to the I-72 terminals by around 14z. Main aviation
forecast challenge will be the development of MVFR ceilings.
Strongest lift/deepest moisture appears to develop mostly north of
I-72...with HRRR consistently dropping cloud bases to MVFR for a
4-6 hour period from mid-morning through early afternoon. As the
showers drop southeast of the TAF sites, have raised ceilings back
to low VFR at KPIA by 19z...then by 21z at KSPI/KDEC/KCMI. The
surface cold front will pass through central Illinois by late
afternoon/early evening, perhaps accompanied by additional
scattered showers. Have therefore held on to VCSH until the
boundary passes and skies clear after the 01z-04z time period.
Winds will initially be SW at 10-15kt, then will veer to NW and
decrease to less than 10kt after FROPA Tuesday evening.

Barnes

&&

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

$$