Area Forecast Discussion

777
FXUS63 KLSX 171902
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
202 PM CDT Sat May 17 2025

.KEY MESSAGES...

- The chance for strong to severe thunderstorms returns to the
  region Sunday night into Monday and again Monday afternoon and
  evening.

&&

.FORECAST DISCUSSION... (Through Next Saturday)
Issued at 201 PM CDT Sat May 17 2025

An active pattern returns to the region Sunday into the beginning of
the work week. A mid-level disturbance moving into the mid-
Mississippi Valley along southwesterly flow will initiate and
organize an MCS that will track east overnight along a warm front
that will be draped across the mid-Mississippi Valley. 1500-2500
J/kg of MUCAPE and 40-60kts of 0-6 km shear will also help
contribute to its organization and maintenance, as well as
provide fuel and organization for individual thunderstorms within
the MCS to become strong to severe. The best location for strong
to severe thunderstorms will be over western and central Missouri
where instability is expected to be highest, most deterministic
guidance sources show instability waning considerably across
eastern Missouri and western Illinois. The main concerns are hail
and winds as these storms are expected to be elevated.

Another mid-level shortwave disturbance will move into the region
Monday afternoon and evening, producing another round of
thunderstorms across the mid-Mississippi Valley. Instability is
expected to be able to rebound back to 1000-3000 J/kg of MUCAPE by
the afternoon hours in the wake of a northward moving warm front.
All hazards are possible with thunderstorms that become strong to
severe.

Delia

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1110 AM CDT Sat May 17 2025

Dry and VFR conditions will continue through the period. There is
a 30-50% chance of showers and thunderstorms tonight into Sunday
morning mainly south of the terminals. While I cannot rule out a
stray shower or thunderstorm passing near one of the mid-Missouri
or St. Louis metro terminals, my confidence is not high enough to
include a mention.

Northwesterly winds will remain gusty through the afternoon,
diminishing in speed early this evening and becoming variable.
Winds will pick back up from the east tomorrow, though with speeds
less than 10 kts.

Delia

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion