153
FXUS63 KLSX 282338
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
638 PM CDT Tue Apr 28 2026

.KEY MESSAGES...

-There remains a 40-90% chance of showers and thunderstorms,
 primarily this evening. A few severe thunderstorms are possible
 across parts of southeast Missouri and southwest Illinois through early
 this evening.

-Mainly dry weather is expected the rest of the week with below
 normal temperatures.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 351 PM CDT Tue Apr 28 2026

Numerous thunderstorms have developed this afternoon across central
and southern Missouri in advance of a shortwave trough currently
over the central Plains.  Most of the severe thunderstorms have
produced large hail as the instability is elevated given that the
surface front now extends from the lower Ohio Valley into northern
Arkansas. The latest RAP is showing an increase MUCAPE values
increasing into the 1000-1500 J/kg through the late afternoon with
deep layer shear in the 40 to 50 knot range supporting isolated
supercells producing large hail over central and southeast Missouri.
 Additional thunderstorms are developing and will likely congeal
over southwest Missouri later this afternoon and this evening which
will pose a damaging wind threat over the far southern part of the
CWA.  As the upper trough moves east, large scale ascent will
increase across the area supporting the 40-90% HREF probabilities,
particularly over the southeast half of the CWA.  This precipitation
will move out of the area late tonight behind the trough and we will
see dry weather the Wednesday and Wednesday night as a surface high
moves into Missouri and Illinois.

With weak cold air advection, highs will only be in the 60s on
Wednesday and lows on Wednesday night will be in the lower to mid
40s which will be 5 to 10 degrees below normal.

Britt

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 351 PM CDT Tue Apr 28 2026

After this system, the weather is expected to be mainly dry except
for late Thursday into Thursday night when another weak shortwave
trough will move across the area bringing 20% chance of showers and
thunderstorms along southward moving cold front.  The LREF is showing
the upper flow going from quasi-zonal to northwesterly over the
Midwest from midweek into the weekend which supports below normal
temperatures into the weekend.

Britt

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 636 PM CDT Tue Apr 28 2026

The threat for scattered showers and thunderstorms will continue
into the overnight hours, mainly impacting KSUS, KSTL, and KCPS
with reduced visibility and lightning. This activity is expected
to remain just east of KCOU and KJEF, and well south of KUIN. As
this weather system moves eastward, dry air will move into the
region and reduce rain chances and improve ceilings later tonight.
VFR flight conditions are then expected through the remainder of
the period.

Elmore

&&

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

$$

WFO LSX