731
FXUS63 KILX 130804
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
304 AM CDT Tue Aug 13 2024

.KEY MESSAGES...

- Severe thunderstorms are possible Thursday evening as a cold
  front pushes into the area.

- Mild and dry conditions will return to central Illinois by the
  weekend into early next week.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 304 AM CDT Tue Aug 13 2024

High pressure anchored from the Upper Midwest E/SE into the
Appalachians will continue to be the dominant weather feature
across central Illinois today. The end result will be a partly
sunny and mild day with highs in the upper 70s/lower 80s. As the
high shifts further eastward, the prevailing baroclinic zone
currently extending from the lee of the Rockies into the Southern
Plains will begin to lift northward tonight. 00z Aug 13 models
agree that convection associated with the nocturnal low-level jet
will develop across Kansas into Missouri and will remain W/SW of
the KILX CWA through dawn Wednesday. This activity will gradually
shift eastward Wednesday morning: however, as the jet weakens and
the precip enters a drier/more subsident environment east of the
Mississippi River, it will dissipate in intensity and areal coverage.
Have added low chance PoPs (20-30%) along/southwest of a
Galesburg...to Taylorville...to Flora line Wednesday morning as
the showers approach.

The slowly advancing warm front will likely extend from southwest
Iowa into the Ozarks by Wednesday evening. Given the nearing front
and increasing boundary layer moisture, have spread low chance
PoPs as far east as I-55 Wednesday afternoon: however, think most
locations will remain dry. As the front moves further eastward and
the nocturnal low-level jet strengthens, convection will blossom
across Iowa/Missouri/western Illinois by late evening...then will
spill into much of central Illinois overnight. Based on model
consensus, have added likely to categorical PoPs along/northwest
of a Shelbyville to Danville line after midnight. Any storms that
occur will be elevated in nature and will pose minimal severe
weather risk. Gusty winds, small hail, and locally heavy downpours
will be possible with the strongest cells.

Barnes

.LONG TERM...(Thursday through Monday)
Issued at 304 AM CDT Tue Aug 13 2024

Showers/storms will be ongoing along/north of I-70 Thursday
morning...with the activity quickly shifting into Indiana and
dissipating toward midday. A lull in precip chances will then
occur for much of the afternoon until an approaching cold front
activates toward sunset. As boundary layer flow veers from SE to
S/SW, higher dewpoint air will return...leading to a highly
unstable environment with SBCAPEs exceeding 3000J/kg. At the same
time, a modest increase in deep-layer shear will set the stage for
strong to potentially severe thunderstorms along the cold front
by evening. 00z Aug 13 GEFS shows a 10-20% chance of SBCAPEs
exceeding 500J/kg and bulk shear increasing to greater than 40kt.
At this time, think the primary risks from the storms will be
pockets of damaging wind gusts around 60mph and hail larger than
quarters between 5pm and midnight.

As surface low pressure tracks from Iowa into the Great Lakes, it
will drag the cold front across central Illinois late Thursday
night into Friday. There is still some potential for strong
thunderstorms along the front by peak heating Friday: however,
latest guidance suggests this may occur a bit further east into
Indiana. Have maintained low chance PoPs for thunder during the
day Friday until the front passes.

After that, a return to mild and mostly dry weather is
anticipated Saturday through Tuesday with high temperatures
remaining slightly below normal for this time of year in the lower
80s.

Barnes

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1143 PM CDT Mon Aug 12 2024

Rain showers have shifted east of all our terminal sites, leaving
variable cloud cover across central IL. Clearing has developed
north of I-74 from PIA to BMI to CMI. HRRR/HREF output continue to
advertise a return of clouds from the west along I-74, but light
fog will become increasingly possible the longer that clearing
remains across that area. Some MVFR and IFR ceilings are not far
off to the west and I would not be surprised to see PIA and/or SPI
have an MVFR ceiling develop later tonight. Actually seeing IFR
cig and vis forecast by several CAMs in SPI later tonight. Since fog
potential continues for the other terminals, we continued with
MVFR vis later tonight for all but SPI, where IFR vis was
forecast. Clearing is expected during the morning tomorrow, but
did not jump on that just yet with the expansive cloud cover
upstream. Winds will remain light and variable under the weak
pressure gradient.

Shimon

&&

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

$$