Mehlville, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

136
FXUS63 KLSX 041956
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
256 PM CDT Mon May 4 2026

.KEY MESSAGES...

- Showers and thunderstorms are expected tonight. Some storms may
  be severe with 1 to 1 1/2 inch hail this evening, primarily a.
  long and north of I-70. There may also be damaging winds,
  however this is not as likely as large hail.

- Periods of rain will continue on Tuesday as a cold front moves
  through the area.

- Temperatures will be below normal Tuesday through Thursday, but
  will warm back up for Friday into the weekend.

&&

.SHORT TERM...  (Through Late Tuesday Night)
Issued at 255 PM CDT Mon May 4 2026

A cold front which is currently stretching from northeast Kansas
into northwest Missouri and southwest/central Iowa will move
slowly southeast through Missouri and Illinois over the next 24-36
hours. Latest RAP and GFS show as much as 2000-2500 J/Kg of
MUCAPE across parts of central and northeast Missouri late this
afternoon into early this evening with around 30kts of deep-layer
shear. However, they also show a good deal of CINH capping the
boundary layer. The CINH will likely lead to only sparse
development of storms this evening, at least initially. There is
enough CAPE and shear to support severe storms, but any storms
that do form are not expected to be rooted in the boundary layer,
so large hail will be the primary threat. Damaging wind gusts are
less likely, though still possible if a particularly strong storm
dumps its core and produces a microburst. A modest low level jet
will develop ahead of the front closer to midnight which produces
moderate moisture convergence across the area. This will lead to
an increase in thunderstorm coverage overnight, but instability
will be decreasing rapidly by that time. Even though there will be
more storms after midnight it is unlikely they will be severe.

The cold front continues moving slowly southeast through the area on
Tuesday with moderate to occasionally strong low level moisture
convergence ahead of an 850mb low over the eastern Plains.  This
will lead to widespread across most of the area.  Clouds and rain
will keep temperatures cool with little chance for the atmosphere to
become unstable through the day.  While there will likely be some
rumbles of thunder through the day, severe storms are unlikely due
to lack of instability.  Rain should taper off from west to east
through the evening.

Carney

&&

.LONG TERM...  (Wednesday through Next Monday)
Issued at 255 PM CDT Mon May 4 2026

The upper level trough axis digs into the Great Plains on Wednesday
which forces the cold front farther south into the lower Mississippi
Valley.  A cool high pressure system builds into Missouri and
Illinois, however the approaching trough produces moderate to strong
mid level frontogenesis over Missouri and Illinois.  The GFS and to
a lesser extent the NAM print out some light QPF due to the
frontogenesis, but forecast soundings show a dry layer near the
surface associated with the approaching surface high.  Think chance
PoPs remain appropriate in this situation.  Northerly flow, with
clouds and potential showers will likely make Wednesday the coolest
day of the next 7 with highs struggling into the mid to upper 50s.
Temperatures warm back into the mid 60s, and then to near normal in
the 70s for Friday through Sunday as the long wave trough moves east
and the upper level flow becomes more zonal.  There will be a brief
chance for rain Friday as a weak short wave moves across the Mid
Mississippi Valle, but the next substantial chance for rain holds
off until Sunday ahead of the next upstream cold front.  The LREF is
showing a good deal of uncertainty with regards to the amplitude of
the trough which is driving this cold front.  This translates into
low confidence in the position of the front, and wide variations in
the temperature forecast. The interquartile range of high
temperatures is 10+ degrees on Sunday, and around 8 degrees on
Monday behind the cold front.  With that in mind, it does look
cooler on Monday with around a 10 degree drop in mean temperatures,
and deterministic guidance cools from the mid to upper 70s on Sunday
in most locations to the upper 60s and low 70s.

Carney

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1247 PM CDT Mon May 4 2026

Scattered showers and thunderstorms will continue this afternoon
and into the evening, mainly across parts of eastern Missouri and
southwest Illinois. The storms will be capable of brief heavy rain
which could lower the visibility to 3 miles or less. The strongest
storms may also produce small hail. Additional thunderstorm
development is expected this evening ahead of a cold front across
northeast and central Missouri. Isolated storms could produce 1
inch or larger diameter hail and wind gusts to 50kts, mainly along
and north of I-70. Widespread showers will continue on Tuesday
morning behind the cold front with ceilings falling low MVFR along
and south of I-70, and IFR across the eastern Ozarks.

Carney

&&

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

$$

WFO LSX