233
FXUS63 KLSX 090343
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1043 PM CDT Wed May 8 2024

.KEY MESSAGES...

- Scattered strong to severe thunderstorms will persist through
  early this evening. All hazards are expected: large hail,
  damaging winds, isolated tornadoes, as well as flash flooding.

- A period of much needed calmer weather and cooler temperatures is
  expected to end the week and continue through the weekend.


&&

.SHORT TERM...  (Through Late Thursday Night)
Issued at 344 PM CDT Wed May 8 2024

(Late This Afternoon Through Tonight)

As of 3 pm, outflow from the activity continues to sink south and
extends from just north of Springfield, MO to just south of
Carbondale, IL. The warm sector along and south of the boundary
remains quite unstable with MU CAPEs in excess of 3000 J/kg, ML
lapse rates of 7-8C/km and 0-6km bulk shear 50-60kts. Also, the
ongoing activity, over far southeastern sections of CWA, has
congealed into a line with embedded supercells, while further west,
in NWS Springfield`s area, discrete supercells are forming along
the outflow boundary. These storms will slide east northeast
moving into the southern portions of the CWA by 21z. Therefore,
there remains a tornado threat as well as large hail possible.
North of the outflow boundary, could see scattered strong to
severe storms with the main threat being large hail.

Otherwise, as the surface low over NE OK lifts northeastward it will
drag a cold front eastward through the forecast area, with the
precipitation tapering off from west to east. The front will exit
the region by 05z Thursday.

Still some concern for isolated flash flooding as some storms may
train over the area, especially south of I-70. So will not make any
adjustments to the Flash Flood watch at this time.

Lows tonight will be in the low 50s to low 60s.

(Thursday through Thursday Night)

On Thursday, a secondary shortwave/cold front on the backside of the
system will slide southeast through the region. So expect increasing
clouds, especially north of I-70. Otherwise, there will be enough
moisture and weak instability to generate scattered showers and a
few thunderstorms over portions of northeast Missouri and west
central Illinois late morning through early evening. Otherwise,
highs on Thursday will be near normal in the upper 60s to upper 70s.
Lows Thursday night will be in the upper 40s to low 50s.

Byrd
&&

.LONG TERM...  (Friday through Next Wednesday)
Issued at 344 PM CDT Wed May 8 2024

Cooler and drier weather through the rest of the work week and
into the weekend. Beyond that, upper level trough over the western
CONUS will begin to lift out towards the region with chances of
showers and storms late on Sunday through mid week. Still a lot of
timing, strength and location differences among the ensembles and
deterministic models, so stuck with the latest NBM solution.
Temperatures will moderate through the period with highs in the
mid 70s to low 80s.

Byrd

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1035 PM CDT Wed May 8 2024

While an isolated shower/thunderstorm cannot be totally ruled out,
the best threat has shifted well off to the southeast of the
terminals with dry weather likely the remainder of the night into
Thursday morning. Scattered showers may impact KUIN in the
afternoon hours, but they should stay north of the other
terminals.

A cold front is near KCOU/KJEF and should approach KUIN over the
next 1-2 hours. Metro terminals will be closer to 0600-0800 UTC.
Near the front, winds are light and variable. Upstream
observations (including at KCOU/KJEF) have shown some patchy (and
at times dense) fog development in areas of clearing. The recent
rainfall is also helping. Therefore, would not be surprised to see
a brief period (~1 hour or so) of some fog at the metro and KUIN
terminals over the next few hours. However, any fog should be
short lived as winds behind the front pick up enough out of the
west/northwest to improve visibilites back to VFR. The threat
overnight into Thursday morning should be more on low stratus.
Model guidance is all over the place, but I could see some high
IFR/low MVFR ceilings late tonight into early Thursday morning.
Best chances appear to be at the metro and KUIN terminals.
Conditions should improve from west to east late tonight through
Thursday morning.

Gosselin

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX