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000
FXUS63 KILX 181512
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1012 AM CDT Thu Apr 18 2024

.KEY MESSAGES...

- Severe threat remains for counties along and south of a line
  from Schuyler to Vermilion counties. The greatest risk
  (enhanced, level 3/5) is located from Scott to Clark counties
  and south.

- The system should be entering west-central Illinois by 10-11am
  and exit southeastern Illinois by midnight tonight. Storm mode
  is expected to be QLCS in nature. However, supercells could
  develop early on.

- There is a 30-40% chance of temperatures dropping below freezing
  Sunday morning for areas north of I-72 and west of I-55.

&&

.UPDATE...
Issued at 1010 AM CDT Thu Apr 18 2024

Mesoscale complex of convection tracking northeastward toward the
IL river late this morning and has been sub-severe and weakening.
Mostly cloudy to overcast skies over much of CWA this morning with
more sunshine over Lawrence county in far southeast IL. Surface
map shows 1009 mb low pressure over north central OK near KS
border with its warm front extending into central MO and sw south
of St Louis and ne of Carbondale IL. East to SE winds turn
southerly in warm sector and dewpoints rise into the low to mid
60s.

Latest CAMs show convection weakening as it moves into central IL
into midday. More widespread and stronger convection to develop
late afternoon/early evening as low pressure lifts into sw IL by
00Z/7 pm with warm front lifting northward toward I-72. Strong to
severe storms expected to move across central and se CWA from late
afternoon through mid evening and still some timing differences
with evolving band/line of convection from latest CAMs. SPC day1
outlook has Enhanced risk of severe storms from Litchfield to
Effingham to Robinson south with slight risk as far north as
Quincy to Lincoln to Champaign and Danville. Marginal risk as far
north as Keokuk Iowa, Peoria and Pontiac. All severe wx parameters
as play including a few tornadoes in southern CWA, though
damaging winds main severe wx threat followed by large hail. Highs
range from near 60F at Galesburg to upper 70s from I-72 south with
lower 80s in southeast IL.

07

&&

.DISCUSSION...
Issued at 310 AM CDT Thu Apr 18 2024

Good morning, central Illinois! As the world wakes, we prep for
another round of severe weather this afternoon. The 00z NAMNest and
HRRR, along with a couple HRW models, indicate that the showers and
thunderstorms will enter west-central Illinois by 15-17z (10am-
12pm). This early round will primarily affect areas north of I-72.
There could potentially be some supercells around/after noon, ahead
of the line of storms arrival. The line of storms we are most
concerned about develops and arrives from the west by mid-afternoon
(21-22z, 4-5pm). The system should be departing the southeastern
counties by midnight tonight.

Today`s hazards primarily should be damaging winds and isolated
tornadoes. The biggest risk for tornadoes looks to be closest to the
low track. The low is progged to track along the I-72 corridor,
where the SPC has placed the 5% tor risk and 30% damaging wind risk
regions. That area is where the higher sig tor parameter values can
be found (values: 1-2). 0-6km bulk shear values range from 30-40
knots ahead of the front which could support the early, discrete
cells. Along the front, as the QLCS moves across the state, the 0-3
km shear vectors are practically parallel to the boundary. This
points towards the line having damaging winds as the main threat,
but spin ups can`t be completely ruled out, especially closer to the
low center track. SPC has a slight risk (level 2/5) for along and
south of a line from Schuyler to Vermilion counties. The greatest
risk (enhanced, level 3/5) is located from Scott to Clark counties
and south.

Following the cold frontal passage this evening, colder temperatures
will move into the state. We will be going from well above normal
temperatures to below normal temperatures. Overnight lows will get
pretty chilly this weekend, with lows in the 30s. There is a
frost/freeze threat as the CWA is within growing season and many
sensitive vegetation types are blooming. Saturday night into Sunday
morning will be the coldest night of the weekend. There is a 30-40%
chance of temperatures dropping below freezing Sunday morning for
areas north of I-72 and west of I-55. After Sunday, temperatures
will begin to warm back up for the new week.

The weekend appears to be dry, albeit chilly. The next chance for
showers comes Monday afternoon.

Copple

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 600 AM CDT Thu Apr 18 2024

A strong cold front is set to move across central Illinois. Some
showers and thunderstorms could move through the northern sites
(BMI/PIA) around noon before the main round. A line of strong
thunderstorms will move through the area this afternoon/evening.
Lowered visibilities are possible as the storms move over. MVFR
ceilings will accompany the low passage, along with a brief window
of IFR for SPI/BMI/PIA. VFR ceilings and visibilities are expected
to return overnight before 12z tomorrow morning.

Copple

&&

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

$$