673
FXUS63 KLSX 080959
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
459 AM CDT Sun Mar 8 2026

.KEY MESSAGES...

- Near record temperatures are possible on Monday and Tuesday.

- Widespread showers and thunderstorms are expected Tuesday into
Wednesday with the potential for a few severe thunderstorms.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 458 AM CDT Sun Mar 8 2026

The latest nighttime microphysics satellite imagery is showing some
valley fog over parts of central and southeast Missouri where the
high clouds have cleared out. This is in the same area that the
latest surface analysis is showing light winds in a surface ridge
axis that extends from southeast Kansas through east central
Missouri into southwest Illinois.  There will continue to be a
window through around sunrise for this fog to continue to develop
before both the ridge and the high clouds shifts to the southeast
causing winds to pick up from the southwest.  Before then, there
could be some locally dense fog in the river valleys across parts of
central and southeast Missouri.

Dry weather is expected through tomorrow as the HREF has the upper
pattern switching to quasi-zonal flow with none of its members
producing any precipitation.  With winds turning out of the
southwest today and plenty of sun, highs will climb into the 60s
today and 70s on Monday.  Forecast soundings are showing mixing up
to 850mb on Monday afternoon supporting the potential for a few
sites to approach record highs (see climate section).

Britt

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 458 AM CDT Sun Mar 8 2026


Then the focus turns to the next storm system and the potential for
severe thunderstorms on Tuesday afternoon and evening.  The latest
runs on the deterministic models are showing decent agreement that
the upper flow will turn southwesterly Tuesday/Tuesday night in
advance of trough that will be digging into the central CONUS.  The
CWA is expected to lie in the open warm sector during the day on as
a surface low moves from northeast Kansas into northern Illinois.
The LREF is showing strong instability developing during the day
with 60-90% of its members having SBCAPE >1000 J/kg during the day
at the same time 40-60% of it members have >40 knots of deep layer
shear indicating the potential for organized convection including
supercells or line segments.  The most likely location for
thunderstorm development will be over the northern CWA which will
closest to the warm front and surface low track.  Given the
potential for supercells, large hail, a few tornadoes, and damaging
winds will be possible.   There will also be some potential for
thunderstorm development during the day farther south in the warm
sector, but this area will be largely capped.  As the low moves to
the east, a cold front will move south across the area during the
night pushing the line of thunderstorms to the southeast. Current
model guidance is showing the instability waning quickly in the
evening which will cause the coverage of strong to severe
thunderstorm to decrease as it moves to the southeast.

This system will also bring widespread coverage of showers and
thunderstorms with the LREF continuing to show 70-90% of its members
producing rain at St. Louis from late Tuesday into Wednesday
morning.  The LREF is currently showing 30-60% of its members having
more than 1" of rain with this system across then entire area. With
the upper flow parallel the upper flow, there will also be the
potential for thunderstorms to train which could cause additional
locally heavy rainfall given that PWATS be in the 99th percentile.

Tuesday looks to have with highs around 80 degrees given similar
conditions to Monday before the cold front moves through the area
causing temperatures to drop back into the 50s and 60s the rest of
the week.

Britt

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 958 PM CST Sat Mar 7 2026

An MVFR stratus field continues to slowly push eastward this evening
and has cleared the central Missouri terminals and KUIN within the
last hour. This deck has been obscured on satellite imagery by an
overcast mid-level cloud field, which has made it tough to
accurately time the exit of the MVFR stratus for the STL metro
terminals. Regardless, based on upstream observations, an exit of
06z for the MVFR stratus and the mid-level clouds still appears to
be a good estimate. With clearing expected around 06z, the formation
of fog becomes a concern, particularly for the river valley
locations along and south of the I-70 corridor, where calmer surface
winds will be in place. As a result, a TEMPO group has been added at
KSUS, KJEF, and KCPS for MVFR visibilities later tonight between 10-
14z. Winds remain light overnight with southwesterly winds picking
up after sunrise gusting to 20kts across northern and central
Missouri before fading off and becoming more southerly Sunday
night.

Peine/Elmore

&&

.CLIMATE...
Issued at 211 PM CST Sat Mar 7 2026

Daily record high temperatures may be threatened both on Monday 3/9
and Tuesday 3/10. Below are the records for each day from our
official climate sites:

            Monday 3/9          Tuesday 3/10
KSTL        80F (1925)          86F (1955)
KCOU        80F (1986)          82F (1955)
KUIN        75F (1986)          79F (1955)


Gosselin


&&

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

$$

WFO LSX