051
FXUS63 KLSX 220904
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
404 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 06z TAFs through 06z Sunday Night)
Issued at 1044 PM CDT Sat Sep 21 2024

VFR conditions are expected for a few more hours with isolated
showers moving through eastern sections of Missouri prior to 06z.
Conditions deteriorate around 06z with showers and thunderstorms
moving in from west to east. Just prior to 04z this evening,
showers and thunderstorms spread from near the MO/IA border
through west-central MO and into the southern Plains. This broad
mass of activity will translate eastward overnight through into
Sunday morning. MVFR ceiling/visibilities will be the primary
impact with localize pockets of IFR possible at any terminals
directly impacted by thunderstorms. This potential is greatest at
KCOU/KJEF. While these conditions cannot be ruled out at KUIN and
metro terminals, thunderstorms will likely weaken somewhat as they
track east early Sunday morning.

Though a bulk of the precipitation was originally expected to
shift east through mid-morning Sunday, some of the latest trends
in data show a slightly southward shift in the axis of heavier
rainfall. If this trend continues, impact may extend slightly
later into the morning. There is a brief lull behind this initial
wave and the arrival of the cold front Sunday evening, when
activity flares up again along and ahead of the front. The
position of the front will determine exact placement of higher
potential Sunday evening, but the general consensus if for
rainfall to shift southeast of KUIN/KCOU/KJEF around 00z and metro
terminal after 02z-03z. A few isolated showers may linger with
MVFR ceilings along and behind the front. VFR could make a return
at KUIN before the end of the TAF period.

Maples

&&

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

$$

WFO LSX