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259
FXUS63 KILX 251814
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
114 PM CDT Wed Sep 25 2024

.KEY MESSAGES...

- An isolated light rain shower is possible in eastern IL this
  afternoon, otherwise much of the area will be dry through
  tonight. More sunshine is expected over the IL river valley
  today while partly to mostly cloudy skies prevail in southeast
  IL. Seasonably cool highs in the low to mid 70s today.

- A prolonged period of unsettled weather is expected late this
  work week into early next week. A chance of showers occurs on
  Thursday afternoon and evening in southeast IL, and into central
  IL too on Friday and Fri night, and continuing through the
  weekend. More widespread showers and the heaviest rainfall is
  expected Friday and Friday night south of I-72 where 1 to 2
  inches is expected in southeast IL and possibly higher amounts
  south of I-70. Breezy northeast winds will prevail Friday
  through Saturday over the area.

&&

.UPDATE...
Issued at 1042 AM CDT Wed Sep 25 2024

Clear skies will continue over most of the CWA with some clouds
lingering in eastern IL. The mid level trough extended from the
upper level system centered over St Louis to the north-northeast
into northwest IN. Isolated showers could still develop along this
trough later this afternoon, though forcing and instability are
minimal, so will keep low chance (20%) pops going for the
afternoon...in the east. Otherwise, dry weather still expected
over the remainder of the CWA through the afternoon and into
tonight. Forecasted highs in the middle 70s across the CWA still
looks like a good forecast, along with light northerly winds.
Therefore, no update planned at this time as the forecast still
looks good.

Auten

&&

.DISCUSSION...
Issued at 400 AM CDT Wed Sep 25 2024

Early morning surface map shows 1006 mb low pressure near Saginaw
Bay MI with its cold front extending southward through western
Ohio into central parts of KY/TN. A weak surface trof extended sw
from the low over the IL river valley and into northern MO. IR
satellite loop and surface obs show broken low/mid clouds in
eastern IL and patchy cloud cover west of I-57. Very patchy fog
over CWA as Lacon had a brief period of dense fog with vsby
1/4-1/2 mile from 115-215 am. Patchy dense fog more common in
northeast IL early this morning. Aloft a 566 dm 500 mb low was
over east central MO near the IL border/MS river close to St Louis
and digging southward.

Latest 00Z model suite weaken the cutoff low a bit to 570 dm at it
tracks into southern IL by sunset. Very weak instability in
eastern IL this afternoon and could see an isolated light shower
develop during peak heating of the afternoon hours. Otherwise weak
surface high pressure ridge moving over the western Great Lakes
and Iowa this afternoon to bring more dry air and sunshine to nw
CWA/IL river valley while partly to mostly cloudy skies linger in
east central and southeast IL. Highs today in the low to mid 70s
and likely warmest nw of the IL river where more sunshine
expected. An isolated light shower possible in southeast IL early
this evening until sunset, otherwise fair weather as clouds
continue to decrease from the nw. Cooler lows in the low to mid
50s in central IL and upper 50s se of I-70.

Forecast models take cutoff low southward to near Memphis TN by
sunset Thursday and will help influence move of remnant of Helene.
Tropical Storm Helene with winds of 65 mph near the ne tip of the
Yucatan Peninsula of Mexico at 4 am cdt is forecast by NHC to
become a hurricane during this morning and eventually a major
hurricane with winds to 120 mph with landfall forecast by Florida
Big Bend early Thu evening. Remnants of hurricane Helene to track
into central TN Fri afternoon and near the western KY/TN border
Sat and Sat night. This track has trended further south along with
the heavier rainfall and rain chances. Thu now looks drier over
central IL with 20-30% chance of showers in southeast IL mainly
southeast of I-70 Thu afternoon as skies become mostly cloudy
there, while partly to mostly sunny skies prevail in central IL.
Highs in the mid to upper 70s Thu, warmest from the IL river
valley nw where more sunshine expected.

Shower chances appear to get as far north as a Shelbyville to
Paris line later Thu night and to near I-72 by Fri afternoon.
Northern and nw CWA could still stay dry on Friday. Tightening
pressure gradient on Friday to increase NE winds to breezy levels
with gusts to 30 mph. Highs Fri range from lower 70s in southeast
IL where showers are likely, to the upper 70s from Peoria nw where
it likely stays dry. Rain chances appear to get further nw into
central IL and IL river valley overnight Fri night and Saturday
while southeast IL likely sees likely to categorical pops Fri and
Fri night when heavier QPF expected there of 1-2 inches and
possibly heavier over Clay, Richland and Lawrence counties. Areas
nw of the IL river now appear to have only light qpf amounts less
than a quarter inch. Breezy NE winds continue on Saturday.

The cutoff low that dips down into MS on Fri to absorb remnants of
Helene late this week and then gradually shift from the mid MS
river valley Fri night ne into the eastern Ohio river valley by
Sunday evening. Rain showers could linger Sunday but now appear to
start pushing se of central IL during Sunday night push se of
central IL and se of Southeast IL on Monday as upper level ridge
shifts into IL on Monday from strong subtropical ridge over the 4
corners in Southwest US. Monday looks nicer with decreasing clouds
and highs in the upper 70s to around 80F. A northern stream trof
passing through the Great Lakes on Monday night and Tue to bring a
cold front se through central IL during Monday night and mostly
passes through dry with limited moisture and better forcing to the
north in the Great Lakes. Cooler temperatures arrive behind this
front Tuesday with highs in the mid to upper 60s next Wed and lows
in the 40s Tue and Wed night of next week.

07

&&

.AVIATION...  
-- Changed Discussion --
(For the 18z TAFs through 18z Thursday Afternoon)
Issued at 115 PM CDT Wed Sep 25 2024

VFR conditions will prevail at all TAF sites next 24hrs. Scattered
CU at 5kft will prevail this afternoon but dissipate this evening
after sunset. Then clear skies are expected through the night into
tomorrow. Winds will be light northerly this afternoon and then
become light and variable this evening, lasting through the night.

Auten
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&&

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

$$