383
FXUS63 KLSX 221118
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
618 AM CDT Sun Sep 22 2024

.KEY MESSAGES...

-There will continue to be chances for showers and thunderstorms
 through Tuesday.

-Isolated severe storms are possible over southeast Missouri and southwest
 Illinois this afternoon and early this evening. The primary
 threat with the strongest storms will be damaging winds.

-Temperatures will cool down behind a cold front today with below
 normal highs on Monday and Tuesday.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 403 AM CDT Sun Sep 22 2024

Initial round of showers and thunderstorms is moving through the CWA
this morning ahead of the cold front in a band of strong low level
moisture convergence.  This first round will eventually exit to the
east by mid-morning as the low level jet veers and weakens. There
will continue to be lesser chances (30-50%) for showers and
thunderstorms this afternoon into this evening as the cold front
that is currently over southeastern Iowa and northwest Missouri will
move southeast across the CWA.  There still remains the possibility
for one or two storms to produce damaging microbursts over southeast
Missouri into southern Illinois this afternoon and early this evening
given MLCAPES around 1500 J/kg and deep layer shear around 30 knots.
There will be some potential for locally heavy rainfall given that
PWATS will be in the 1.6-2" range today, especially where any storms
can train for very long.

The chance for showers and thunderstorms will begin to increase
again late tonight into Monday, particularly over the southern half
of the CWA.  Lift will increase across Missouri and Illinois as the
HREF is showing an upper trough moving into the area from the west.
Have kept higher PoPs (60-80%) over the southern half of the CWA
where the stronger forcing and the best moisture transport will move
into the area late tonight into tomorrow afternoon.

There will be quite a range in highs today with the front and rain,
ranging from near 70 over the north to the middle 80s in the south.
Highs tomorrow will be below normal across the CWA with cold air
advection behind the front, the clouds, and rain chances.

Britt

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 403 AM CDT Sun Sep 22 2024

There is decent agreement amongst the medium range models that upper
trough will drop down into the Midwest behind Monday`s trough which
will keep showers and thunderstorms going over the area Monday night
into Tuesday.   Some solutions show an upper low cutting off over
the Midwest into late week which would keep a chance (20-30%) of
showers going over the CWA Thursday into Saturday.

Temperatures will still be below normal on Tuesday, but will climb
back to near normal the rest of the week.

Britt

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 611 AM CDT Sun Sep 22 2024

A round of showers and thunderstorms will move through the
terminals through 15Z bringing MVFR and some IFR conditions along
with occasional moderate to heavy rainfall. These conditions will
move out of the area by mid morning leaving most of the rest of
the day mainly dry with just of chance (20-40%) of additional
showers and thunderstorms. Confidence in timing is too low to
include in the TAFs at this time. There is reasonable confidence
to include additional thunderstorms at COU/JEF after 06Z tonight.
Additional thunderstorms will also be possible after 12Z at STL
tomorrow. After conditions will improve to VFR today, ceilings are
expected to go back to MVFR tonight.

Britt

&&

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

$$

WFO LSX