Valley Park, Missouri Weather Forecast Discussion

876
FXUS63 KLSX 150833
AFDLSX
Area Forecast Discussion
National Weather Service Saint Louis MO
333 AM CDT Mon Sep 15 2025
.KEY MESSAGES...
- Hot weather is expected through Thursday with some relief likely
  by the end of the week.
- There is a chance of thunderstorms over parts of the area each
  day, with the best chance (30-60%) across much of the area
  Thursday night into Saturday.
&&
.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 331 AM CDT Mon Sep 15 2025
Scattered thunderstorms currently drifting over central and
southeast Missouri will likely dissipate in the next few hours as
the RAP is showing low level convergence weakening. The rest of the
morning is expected to be mainly dry before additional scattered
showers and thunderstorms (20-30% chance) develop by early afternoon
across the western half of the CWA. These storms will occur on the
western periphery of the upper ridge where the RAP is showing some
surface convergence this afternoon.  Like yesterday, I could not
rule out one or two stronger wind gusts this afternoon (>45 mph)
with these storms given MLCAPES in the 2000-3000+ J/kg range and
inverted-V soundings seen in the RAP.  The storms will die out by
early this evening with the loss of daytime heating leaving the rest
of tonight dry.
With current temperatures in the 70s, highs today will still climb
into the low to mid 90s.  Lows tonight will drop into the 60s.
Britt
&&
.LONG TERM...  (Tuesday Night through Sunday)
Issued at 331 AM CDT Mon Sep 15 2025
The LREF is showing that the upper high associated with the omega
block will stay in place through Thursday which will continue to
keep forcing for daily scattered showers and thunderstorms confined
over the western part of the CWA.  The omega block will begin to
break down later this week as the western upper trough moves east
across the Midwest increasing the chance of showers and
thunderstorms areawide. 30-60% of the LREF members are producing
precipitation across CWA Thursday night into Saturday supporting
this trend.
With the omega block staying in place, still expect highs to be
mainly in the 90s through Thursday before dropping back into the 80s
and upper 70s as 850mb temperatures fall from 20C to 15C.
Temperatures will also be affected by more clouds and the potential
for clouds and rain.  This is reflected in the NBM IQR at STL which
is only 2-4 degrees through Thursday but then increases to 7 degrees
from Friday on.
Britt
&&
.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1044 PM CDT Sun Sep 14 2025
Isolated showers and thunderstorms will continue to be possible
for much of the night, mainly across parts of southeast and
central Missouri. The strongest storms will be capable of
producing gusty winds and reducing the visibility to 3SM or less
in brief heavy downpours. Any storms that do develop are expected
to dissipate before sunrise. There is a chance for isolated
storms again on Monday afternoon mainly across central Missouri.
VFR flight conditions are expected outside of convection.
Carney
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion