230
FXUS63 KILX 141044
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
544 AM CDT Wed Aug 14 2024

.KEY MESSAGES...

- Showers and thunderstorms will track across central Illinois
  early Thursday morning. Severe weather is not expected, although
  some of the cells may produce small hail and heavy downpours.

- Scattered strong to severe thunderstorms will develop along a
  cold front Thursday evening. Damaging wind gusts of around 60mph
  and hail larger than quarters will be possible.

- Once the cold front passes, mild and dry weather is on tap for
  the upcoming weekend.

&&

.SHORT TERM...(Today through Thursday)
Issued at 337 AM CDT Wed Aug 14 2024

08z/3am surface analysis shows a 1021mb high anchored over the
Great Lakes...while a stationary frontal boundary extends from the
lee of the Rockies southeastward into the Deep South. A large
cluster of thunderstorms has developed north of the boundary on
the nose of a 40-50kt 850mb jet streak across Nebraska. These
storms will eventually outrun their energy source and will
dissipate as they push further eastward toward the drier/subsident
environment across Illinois. CAMs continue to suggest a dry
morning, followed by perhaps a few showers reaching the Illinois
River Valley toward midday. Have included slight chance PoPs
along/west of a Galesburg to Springfield line this afternoon
accordingly, although it appears most areas will remain dry.
After a sunny start to the day, clouds will be on the increase
from west to east as the day progresses. High temperatures will be
a couple of degrees warmer than yesterday in the middle 80s.

As upper ridging builds over the Plains, the frontal boundary will
get nudged E/NE later today into tonight. Models depict the
nocturnal low-level jet once again strengthening to 40-50kt
tonight, but this time orienting from Oklahoma northeastward into
Iowa. As such, am expecting thunderstorms to initiate west of the
Mississippi River by late evening...with the activity spilling
eastward into central Illinois late tonight into Thursday morning.
Based on 00z Aug 14 models, have focused likely to categorical
PoPs along/west of I-55 after midnight...then further east to the
Indiana border Thursday morning. SBCAPEs will be minimal during
this time frame, so the storms are expected to be elevated in
nature. Given a narrow corridor of MUCAPEs of 1500-2500J/kg, think
some of the stronger cells will be capable of producing small hail
and locally heavy downpours...although the severe weather risk
will remain quite low.

The showers/storms will exit into Indiana toward midday, followed
by a period of warm and dry conditions for the afternoon. With
boundary layer flow veering from SE to S/SW upon passage of the
warm front, higher surface dewpoints in the lower to middle 70s
will contribute to a strongly unstable environment with SBCAPEs
greater than 2500J/kg. In addition, an approaching short-wave
trough will create increasing deep-layer shear as depicted by NAM
0-6km bulk shear values exceeding 40kt by evening. While all the
ingredients will be in place for widespread severe weather,
convergence along the front will not be that strong. As a result,
areal coverage of convection along the cold front may be somewhat
lacking. Think scattered strong to severe storms will form along
the front across eastern Iowa/northern Missouri by late
afternoon...then will push eastward into central Illinois during
the evening. The primary hazards will be damaging wind gusts of
around 60mph and hail larger than quarters between 7pm and 1am.

Barnes

.LONG TERM...(Friday through Tuesday)
Issued at 337 AM CDT Wed Aug 14 2024

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 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 Thursday Morning)
Issued at 544 AM CDT Wed Aug 14 2024

Skies will initially be mostly clear early this morning: however,
mid/high clouds will steadily increase from west to east as the
day progresses with all terminals becoming BKN-OVC during the
afternoon. Convection is expected to develop across Iowa and
northern Missouri this evening, then track eastward into central
Illinois overnight. Exact timing is still somewhat in question:
however, confidence is growing that thunderstorms will reach at
least the western terminals prior to 12z Thu. As a result, have
added predominant thunder and a low VFR ceiling at KPIA after 09z
and at KBMI/KSPI after 10z. Further east, opted to not mention
thunder at either KDEC or KCMI. Winds will be E/NE at around 5kt
early, then will veer to SE and increase to 8-12kt from late
morning through the remainder of the 12z TAF period.

Barnes

&&

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

$$