466
FXUS63 KLSX 070922
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
422 AM CDT Tue May 7 2024

.KEY MESSAGES...

- There is a chance for thunderstorms to redevelop late this
  morning and this afternoon over southeast Missouri and
  southwest Illinois. A few of these storms could be strong to
  severe.

- A greater risk of severe thunderstorms will be on Wednesday when
  the strongest storms will be capable of producing a few strong
  tornadoes and very large hail.

&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 415 AM CDT Tue May 7 2024

Expect the QLCS to continue to move east across the CWA through 8
am.  Latest SPC mesoanalysis is showing MUCAPES on the order of 1000-
2000 J/kg with deep layer shear of 40 knots which will help to
maintain the strength of the line as it moves east across the area
the next few hours in the tornado watch.  The latest RAP is showing
a 50 knot low level jet becoming more veered with time which
supports a continued damaging wind/isolated brief tornado threat
until the line moves out of the CWA.

The RAP/NAM is showing MLCAPES climbing into the 2000-3000 J/kg
range over the southeastern half of the CWA late this morning and
afternoon ahead of the cold front with deep layer shear of 50 knots.
While overall coverage of thunderstorms will be limited by lack of
mid level ascent and convergence along the front, cannot rule out a
few strong to severe thunderstorms capable of producing large hail,
damaging winds and perhaps a brief tornado.

Tonight looks dry as a weak shortwave moves across the area before
an active day develops across the area on Wednesday.  The ridge will
move out of the area leaving a shortwave to approach the area late
in the day from the west.  This will bring a surface low and warm
front north into area north during the day.  There remains questions
on how far north this front will move and will thunderstorms that
develop early in the day affect how much instability is available
for storms to develop later in the day.  The current thinking is
that the front will be able to move as far north as I-70 with
MLCAPES between 2500-3500 J/kg to the south of the front and deep
layer shear of 50-70 knots.  This will be conducive for supercells
both along the warm front and the cold front and in the open warm
sector. Forecast soundings tomorrow afternoon are showing large
clockwise curvature in the low layers which will enhance the
potential for tornadoes including the potential for a few strong
ones. The front will move southeast of the area tomorrow evening.


&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 415 AM CDT Tue May 7 2024

Global models are showing an active pattern continue into the the
weekend with additional chances for showers and thunderstorms.
Temperatures will cool down close to normal Thursday through
Saturday before climbing back above normal Sunday and Monday.


Britt

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1148 PM CDT Mon May 6 2024

Line of strong to severe thunderstorms over western Missouri is
still on track to move into COU/JEF between 07-10Z, UIN between
08-11Z, and the St. Louis terminals between 09-12Z. These
thunderstorms will likely produce MVFR, possible IFR ceilings and
visibilites in brief downpours and strong wind gusts (possibly
between 35-50 knots). The storms will move off to the east by 12Z,
with just a low chance of redevelopment during the day on
Tuesday. MVFR ceilings will linger through 18Z, but mainly dry and
MVFR conditions are expected during the afternoon. Outside of
thunderstorms winds will gust to 20 knots from the south through
mid morning before veering out of the southwest.

Britt

&&

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

$$

WFO LSX