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250
FXUS63 KILX 241755
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1255 PM CDT Tue Sep 24 2024

.KEY MESSAGES...

- Widespread showers and a few thunderstorms will continue today
  across central and southeast IL, gradually diminishing in
  coverage from west to east during this afternoon and early
  evening. Rainfall amounts will be variable today, with some
  areas getting a tenth to quarter inch and others getting as much
  as a half to 1 inch.

- A prolonged period of unsettled weather is expected late this
  work week into early next week, with rainfall starting Thursday
  afternoon and Thursday night, and more widespread showers
  expected Friday into this weekend.

&&

.UPDATE...
Issued at 1101 AM CDT Tue Sep 24 2024

Showers will continue to move northeast across the eastern
portions of the CWA this afternoon as the sfc low moves northeast.
The upper level parts of the system are still west of the CWA and
will move across the area this afternoon into this evening, which
will continue light precip through the period. Have made some
adjustments to pops for the rest of the day and into this evening,
so update should have already gone out reflecting that...though
changes are likely minor.

Auten

&&

.DISCUSSION...
Issued at 400 AM CDT Tue Sep 24 2024

Early morning surface map shows 1008 mb low pressure near St Louis
with its warm front near I-70. Areas of fog had developed past few
hours north of the warm front over much of central IL with
pockets of dense fog along and southeast of a Bloomington to
Quincy line to along I-72. We issued a special weather statement
for areas between the IL river and I-70 for the dense fog
possibility into mid morning. Aside from the fog, radar mosaic
shows an area of showers and a few thunderstorms lifting ne
western and sw CWA especially in nw Knox county and into areas
between Springfield, Taylorville and Litchfield and approaching
Decatur. More widespread convection was just se of IL into south
central and se Indiana supported by a 25-30 kt sw low level jet.
PW values also range from 1.5-1.75 inches, highest in southeast IL
where moderate to heavier rain showers occurred during Monday
evening. Dewpoints ranged from upper 50s from Peoria north to mid
to upper 60s from I-72 south and temps are near dewpoints se of
Peoria along with light to calm winds helping produce widespread
fog.

The latest CAMs lift low pressure ne into north central Indiana by
mid afternoon and pushing cold front east of the Wabash river
around noon today. Showers will be likely this morning with
isolated thunderstorms, and diminishing trends from west to east
during the afternoon as low pressure pulls further ne away from
central IL. SPC Day1 outlook keeps marginal risk of severe storms
east of IL this afternoon with slight risk in central and eastern
KY where stronger instability and wind shear will be ahead of the
cold front. Highs today in the upper 60s to near 70F from I-72
north and mid 70s southeast of I-70 which is in warm sector this
morning. Isolated showers linger in southeast IL early this
evening otherwise quiet weather expected tonight. A few CAM
members show patchy fog late tonight though better chance of fog
development to be over central and northeast Indiana. Cooler lows
tonight in the lower 50s nw of I-55 and upper 50s in southeast
IL.

Weak high pressure tracking from the Central Plains into the
upper MS river valley and western Great Lakes on Wed afternoon
will provide dry weather to areas nw of the IL river. However an
upper level trof near the eastern Dakotas and MN border to deepen
and form a strong cutoff upper level low into southeast MO by Wed
afternoon. The 00Z model suite now showing low chances of light
rain showers by Wed afternoon over portions of central and especially
eastern IL. Highs in the low to mid 70s Wed with more sunshine
possible nw of the IL river where warmest temps may likely be.

National Hurricane Center has Potential Tropical Cyclone Nine
south of western Cuba developing into Hurricane Helena by sunset
Wed as it track northward over the eastern Gulf of Mexico and
reaching the Big Bend of Florida gulf coast by sunset Thu with
winds of 100-110 mph. There is a chance of rain showers lifting
northward into southeast IL Thu morning and into parts of central
IL Thu afternoon, with increasing chances of rain showers from
south to north during Thu night and Friday. Remnants of hurricane
track northward toward south central KY by sunset Friday. The
strong cutoff upper level low meandering over AR Thu and Fri to
likely steer the remnants of this system back into the
lower/middle Ohio river valley Fri night and possibly back into
southern IL Saturday as its absorbed into the cutoff low lifting
into the mid MS river valley Saturday and ne over the Ohio river
valley Monday. Looks like an extended period of unsettled weather
over central and southeast IL late this week through early next
week. Rainfall amounts of 1-2 inches could occur if this track
occurs with 2-3 inches in southeast IL and over 3 inches in sw IL
near the MO border from St Louis south. This would be beneficial
rainfall if it occurs due to the drought that has recently
developed over southern IL and parts of central and northern IL.

07

&&

.AVIATION...  
-- Changed Discussion --
(For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1255 PM CDT Tue Sep 24 2024

MVFR conditions will prevail for the next 2hrs at PIA, 4hrs at
SPI and 5-6hrs at DEC and CMI...except for BMI, which will be IFR
for the next 2hrs and then become MVFR at 20z. This afternoon/this
evening, VFR conditions will occur at all sites with skies
clearing during the early morning hours tomorrow. When this
occurs, light fog will develop for a few hours at PIA, BMI, SPI,
and DEC. Though conditions scatter out at CMI, it will be late
enough that fog will not develop. Light rain has ended at most
locations, except BMI, but based on radar, am going to keep VCSH
at most sites for a few hours...just not at PIA and SPI. Winds
will be west to northwest through the period with speeds less than
10kts.

Auten
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&&

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

$$