249
FXUS63 KILX 150143
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
843 PM CDT Wed Aug 14 2024

.KEY MESSAGES...

- Two periods of thunderstorms are expected Thursday, one early in
  the morning and the other in the mid to late evening. Of these,
  the latter storms have the highest chances for severe weather,
  with damaging winds the greatest concern.

- Locally heavy rain will accompany the showers and storms, though
  probabilities of a widespread 1+" of rain are fairly low.

- After Friday, an extended period of quiet weather is expected
  through the first half of next week.


&&

.UPDATE...
Issued at 841 PM CDT Wed Aug 14 2024

This evening, low pressure is located over SD/NE with a broad
corridor of warm air advection inching east across portions of the
mid Mississippi Valley. A few showers and storms are noted near
the Mississippi River, but 00Z KILX sounding showed dry
conditions up to around 600mb with very weak and capped
instability. As such, this convection forming in the WAA to our
west should struggle as it moves into central Illinois late this
evening. Meanwhile, a more organized line of storms currently over
KS/NE will spread east overnight on a veering LLJ. This will
advect weak instability into portions of the lower Illinois River
Valley late tonight into Thursday morning supporting a decaying
line of showers and storms into the local area.

Deubelbeiss

&&

.SHORT TERM...  (Through Late Thursday Night)
Issued at 302 PM CDT Wed Aug 14 2024

Latest radar mosaics show scattered thunderstorms across central
Missouri into southeast Iowa, in the wake of the earlier MCS which
continues to sink southeast and weaken. Latest HRRR has latched
onto this activity and sneaks it into west central Illinois by 5-6
pm, before weakening. However, orientation of the instability
axis would suggest a southeast motion as well. Will keep some 20%
PoP`s going through late afternoon from about Peoria-Springfield
westward.

Main focus remains with a couple periods of thunderstorm activity
late tonight into Thursday night. Morning high-res models continue
to suggest linear convective initiation across Nebraska and
Kansas very late in the afternoon, with upscale growth into an MCS
during the evening. While the main line still looks to arrive in
our forecast area after 3 am, a few showers may develop ahead of
it on the fringe of the upper jet spreading toward the Mississippi
River. By midday, what`s left of the line should be close to the
I-70 corridor. Severe potential during this period appears low.

Main period of concern for severe weather still appears to be in
the evening. A low level jet will help with renewed storm
development to our west early in the evening. Some variety noted
on the CAM`s with the extent of this development, though most are
pointing toward a period from about 9 pm Thursday to around 2 am
Friday with the highest potential. Damaging winds appear to be the
main focus, though some hail can`t be ruled out if the storms
remain more discrete as they enter the area. In terms of the heavy
rain potential, there remains some fluctuation with the heavier
QPF axis, though precipitable water values peak toward sunrise
Thursday. HREF probabilities of 6-hour rainfall amounts over 1
inch of rain peak around 30% west of Springfield with the early
morning activity, and near Peoria (40-50% chance) with the evening
storms.

Temperature-wise, assuming clouds break up enough by afternoon,
highs should be a few degrees warmer than today, mainly in the mid
80s. However, with a substantial increase in dew points (mid 70s),
heat index values in the low-mid 90s are expected west of Peoria
and Springfield.

Geelhart

.LONG TERM...  (Friday through Next Wednesday)
Issued at 302 PM CDT Wed Aug 14 2024

The longer range pattern will be dominated by an amplifying upper
ridge along the east slopes of the Rockies, which will persist
into the middle of next week. An upper low will slide across the
Great Lakes through the weekend, as a longer wave upper trough
develops. These two features will keep a northwest flow across
Illinois, with temperatures running a few degrees below normal and
no significant surges of low level moisture to add to the
humidity. Some wraparound showers can`t be ruled out on Friday and
Saturday in the cyclonic flow around the low, though better
chances appear closer to the Great Lakes and thus our forecast
will be kept dry for now. After that, surface high pressure will
dominate the Midwest with continued dry conditions.

Geelhart

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 623 PM CDT Wed Aug 14 2024

Thunderstorms are expected to develop and expand in coverage over
MO/IA late this evening and eventually move across central
Illinois late tonight into Thursday morning, likely in a weakening
phase. MVFR or IFR ceilings may accompany the precip and linger
for a few hours Thursday morning. SE winds tonight into Thursday
morning will turn southerly Thursday afternoon and will gust to
around 20kt as conditions return to VFR.

Deubelbeiss

&&

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

$$