201
FXUS63 KLSX 071732
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1232 PM 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 18z TAFs through 18z Wednesday Afternoon)
Issued at 1224 PM CDT Tue May 7 2024

VFR flight conditions are expected to dominate most of the
forecast period. Diurnal instability driven cumulus clouds will
persist across east-central MO into southwest IL during the
afternoon impacting KSTL/KSUS/KCPS. There is also a threat of a
strong isolated thunderstorm in this region through 23-00z,
however the anticipated coverage/probability of a TAF impact is
low and thus it has not been mentioned. Overnight there could be
some MVFR vsbys from radiational fog at KSUS/KCPS from around
09-13z. The next significant round of showers and thunderstorms
will largely be centered on Wednesday afternoon, however I have a
mention as early as 16z at KCOU/KJEF but there is a good amount of
uncertainty in whether they will develop this early in the day.

Glass

&&

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

$$

WFO LSX