241
FXUS63 KLSX 032338
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
538 PM CST Tue Nov 3 2026

.KEY MESSAGES...

- Showers and isolated thunderstorms will exit the area this
  evening. A marginal risk for severe thunderstorms remains in place
  for much of the area, with confidence in these severe storms
  developing the greatest in NE MO and west-central IL.

- A pair of cold fronts will move through the area tonight and
  again on Thursday, dropping temperatures to near seasonal
  normals by the weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 214 PM CST Tue Nov 3 2026

As of 20z, a nearly stacked cyclone was centered over north-central
Missouri. The primary cold front associated with this low extended
to the southwest into extreme SE KS and eastern OK, with a secondary
cold front reaching south/southeast of the low into south-central MO
along the leading edge of the dry slot. The atmosphere ahead of the
secondary front is characterized by relatively high dewpoints and
SSE surface winds. Accordingly, there is 250-500 J/kg of MLCAPE
across eastern MO and western IL. With effective bulk shear in
excess of 50 kts and 0-1km shear in the 30-40 kt range, the
atmosphere remains at least marginally supportive for severe storms
capable of producing damaging winds or a tornado or two. However, up
to this point, areas ahead of the secondary front have remained
capped, significantly limiting the ability for these showers to
develop into thunderstorms.

Between the fronts mentioned above, the atmosphere is less capped,
but dewpoints are lower, surface winds are out of the SSW, and the
low level jet is weaker. This points to an atmosphere less favorable
for severe storms, especially those capable of producing tornadoes.
While we still may see a few thunderstorms develop in these areas
given strong forcing associated with the approach of the primary
front and vorticity advection associated with the upper low, my
confidence in severe storms occurring is low given the above
limiting factors. If severe storms were to develop, they would very
likely be along the secondary cold front, where deeper forcing and
an uncapped atmosphere meet up with deeper moisture and more robust
wind shear.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 214 PM CST Tue Nov 3 2026

Additional low level moisture will wrap back into the region
overnight on the back side of the low, which will reintroduce
low clouds and perhaps some drizzle by tomorrow morning. Dry,
westerly winds will gradually bring in cooler temperatures and
scour this moisture through the day tomorrow, allowing skies to
become more broken or scattered as we approach sunset,
resulting in notably cooler temperatures tomorrow night and
Thursday morning.

On Thursday, an upper trough will traverse the middle CONUS, driving
another cold front through the Middle Mississippi Valley. Guidance
appears to be in relatively good consensus on frontal timing, with
the front arriving in our northern CWA around midday and pushing
through the CWA by late evening. Moisture return ahead of the front
looks fairly weak, so precipitation chances along the front are
fairly low (< 25%). If it does rain, amounts will be light, given
the limited moisture. What will be more notable is that temperatures
are expected to drop behind the front, with the current forecast
calling for temperatures around seasonal normals.

Upper level ridging and surface high pressure will take hold on
Friday and Saturday. This will result in gradually clearing
skies and weakening winds. These factors, coupled with the
cooler and drier airmass in pace behind the late-week fropa,
will set the stage for at least some areas within CWA to approach
of fall below freezing, especially on Sunday morning.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 538 PM CST Tue Nov 3 2026

Showers associated with a surface low in northern MO continue to
traverse east through the area, and are impacting the St. Louis
metro terminals as of 23z. An additional thin line of showers is in
central MO and moving northeast and are expected to briefly impact
KUIN. As the showers move out of the area and the winds begin to die
down this evening, ceilings are expected to lower slightly overnight
but are expected to remain MVFR. As the surface low moves northeast,
some wrap around moisture may cause some drizzle or sprinkles that
impact KUIN and the metro terminals overnight and into the early
morning causing lower visibilities, but confidence is low on whether
or not that will come to fruition so a BR condition was included to
hint at the possibility. On Wednesday, high pressure will move it
and allow clouds to clear returning terminals to VFR conditions.

&&

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

&&

$$

SHORT TERM...BSH
LONG TERM...BSH
AVIATION...Asel/Britt