Des Peres Missouri Weather Forecast Discussion

071
FXUS63 KLSX 071142
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
642 AM CDT Tue Oct 7 2025
.KEY MESSAGES...
-A cool down will kick off today, bringing temperatures back to near
normal through the end of the work week.
-Temperatures will warm back above normal over the weekend and
 into next week with dry conditions.
&&
.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 253 AM CDT Tue Oct 7 2025
As of 2 AM a surface cold front is draped from Pittsfield, IL to
Mexico, MO and making its way southeast through the forecast
area. Scattered showers and thunderstorms are firing off the 850
mb front that is lagging behind the surface front by 60-70 miles.
The surface and elevated fronts will progress southeast through
the day. As they do the 850 mb front is expected to weaken and
coverage of showers and thunderstorms will diminish, though a 20%
chance of rain will stay in the forecast until the front exits the
area. The surface front will exit the region during the forecast
area this morning, while the elevated front and chance for showers
and thunderstorms will exit the CWA this afternoon. Temperatures
ahead of the 850 mb front will warm into the mid to upper 70s
while behind the elevated front temperatures will be near normal
in the upper 60s to low 70s.
A surface high will build into the region behind the cold front,
bringing cooler, drier air into the mid-Mississippi Valley. At the
same time a mid-level trough will exit the Mississippi Valley while
a ridge builds into the Central Plains in its wake, leaving the
region within northwest flow aloft for Wednesday.
Delia
&&
.LONG TERM...  (Wednesday Night through Monday)
Issued at 253 AM CDT Tue Oct 7 2025
The surface high and northwesterly flow will continue into Friday,
keeping the cool, dry continental air in the region. The dry air and
surface high will help temperatures cool effectively. Minimum
temperatures Thursday and Friday morning will fall as much as 10
degrees below normal, in the 40s. Some sheltered areas in the
hollows and river valleys will be able to achieve lows in the upper
30s. High temperatures will be near to slightly above normal in the
low 70s given the cool starts and cooler 850 mb temperatures.
By Saturday the mid-level pattern begins to shift with the axis of
the ridge over the Central Plains shifting eastward and throwing the
mid-Mississippi Valley into southwesterly flow. This, combined with
the eastward shift of the surface high and subsequent southerly
surface flow, results in a warming trend that will continue into
next week. Temperatures will warm back above normal in this pattern,
the 25th percentile of the interquartile spread is above normal
Saturday through the end of the period. Confidence is growing in
this pattern change as ensemble guidance continues to be in good
agreement on the placement of the ridge. Though it should be noted
that shifts in the location of the axis and the timing of this will
impact temperatures. Confidence is higher that the region will be
dry after today`s cold front under the influence of the dry air mass
and then building mid-level ridge. This will further exacerbate the
dry conditions across the region as most will not see any rain from
today`s cold front. As of today, it`s been two weeks since rain
last fell at our climate sites (September 23rd at KSTL, KCOU,
KUIN).
Delia
&&
.AVIATION...  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 603 AM CDT Tue Oct 7 2025
Showers and a few thunderstorms will continue to affect UIN
through 14Z so have include a TEMPO group at that terminal. There
are lesser chances at the other sites, but the chances are too low
to include in the TAFs at this time. IFR/MVFR ceilings will
gradually improve through the day, with VFR conditions expected at
all of the terminals this afternoon. Winds will remains out of the
north around 10 knots through the period.
Britt
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion