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FXUS63 KILX 131050
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
550 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 12z TAFs through 12z Wednesday Morning)
Issued at 549 AM CDT Tue Aug 13 2024

Shallow ground fog has developed across central Illinois early
this morning: however, it has not been creating widespread reduced
visibilities. As a result, have opted to only carry 5-6 miles
prevailing visby through 13z before the fog rapidly dissipates.
The main aviation forecast concern in the immediate short-term is
a band of MVFR ceilings currently along/south of a KUIN to K3LF
line. IR satellite imagery shows the cloud area trying to build
northward: however, with the sun rising and boundary layer flow
from the NE, do not think MVFR will reach KSPI. Forecast soundings
and Cu-rule analysis indicates FEW-SCT diurnal Cu at around
2500-3000ft from late morning through the afternoon...in addition
to SCT mid-level clouds at 8000-10000ft. Winds will initially be
NE at around 5kt, then will veer to E/SE as the day progresses.

Barnes

&&

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

$$