401
FXUS63 KLSX 211732
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1232 PM CDT Sat Sep 21 2024

.KEY MESSAGES...

-Several rounds of showers and thunderstorms are expected through Monday
 night will bring some beneficial rainfall to some areas. The
 best chance (70-90%) will be late tonight into Sunday morning.

-There is the potential for some locally heavy rainfall late
 tonight into Monday. Isolated strong to severe storms are also
 possible over parts of central and southeast Missouri on Sunday
 afternoon and evening.


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 405 AM CDT Sat Sep 21 2024

Latest radar mosaic was showing a complex of showers and
thunderstorms over western Missouri on the nose of the low level jet
early this morning.  The latest runs of the CAMS continue to show
that this complex will weaken as it moves east into the CWA early
this morning as the LLJ veers and weakens.  Have lowered PoPs to 40-
60% over southeast and central MO early this morning based on the
recent trends.  Chances for showers and thunderstorms the rest of
the day into the evening will be dependent on developing along a
warm front moving over the area or any residual outflow boundaries
underneath an upper level ridge.   Will keep chances in the 20-40%
range for now.

Better chance is still late tonight into Sunday as the axis of the
aforementioned upper ridge will begin to shift to the east and an
upper low currently over the southwestern CONUS will lift out and
move into the Plains.   Lift associated with an initial shortwave
trough will move into the area late tonight at the same time that a
cold front will move southeast out of Iowa.  The increase in the low
level jet will bring added moisture with PWATS around 2".   Will
continue with high PoPs (70-90%) late tonight into Sunday morning as
the front will move slowly southeast as it will be aligned with
southwesterly flow aloft.  There may be an isolated strong to severe
storms capable of producing damaging wind gusts on Sunday afternoon
and evening ahead of the slow moving front.   MLCAPES will be in the
1000-2000 J/kg range with deep layer shear range ahead of the front
before it moves south of the area early on Sunday evening.

Highs will be in the 80s to near 90 where the clouds can clear out.
There will be a contrast in temperatures from north to south based
on the front moving through with 70s in the north and 80s in the
south.

Britt

&&

.LONG TERM...  (Sunday Night through Friday)
Issued at 405 AM CDT Sat Sep 21 2024

Will continue with the high PoPs Sunday night into Monday night (50-
80%) as all of the available guidance is showing one or two
additional troughs moving through the area along with an attendant
cold front, though with different timing and strength.  The LREF
does match these high PoPs, with some lower chances on Tuesday
before going dry Tuesday night into Wednesday night as a surface
high  moves through the Midwest.  Will continue with slight chances
for showers at the end of the week as some of the guidance is
showing an upper low over the central CONUS.

Temperatures will be below normal to start next week, with Monday
having highs in the 60s over northwest half of the CWA where there
will clouds, rain, and CAA. Temperatures will gradually climb back
to near normal Wednesday into Friday.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1231 PM CDT Sat Sep 21 2024

This morning`s showers extending from northeast through central
Missouri continue to very slowly diminish in coverage. For this
reason, took VCSH out of the St. Louis metropolitan terminals this
afternoon. There is a slight chance of showers and thunderstorms
through this evening, but coverage and chances are too small to
include mention in the TAFs. Widespread rain with some thunder is
forecast to begin late tonight and continue into tomorrow morning
ahead of a cold front. Winds will shift dramatically during this
time period, making it difficult to choose a direction at any
given terminal. This is exacerbated given the outflow boundaries
in the area and the exiting warm front. Winds during the period
are not expected to be especially gusty, with prevailing winds
generally at 10 kts or less.

Jaja

&&

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

$$

WFO LSX