Saint Louis, Missouri Weather Forecast Discussion

660
FXUS63 KLSX 081110 CCA
AFDLSX
Area Forecast Discussion...CORRECTED
National Weather Service Saint Louis MO
610 AM CDT Mon Sep 8 2025
.KEY MESSAGES...
- While today will be mild, a warming trend begins tomorrow, and
  well above average temperatures are expected Wednesday through
  the end of the weekend.
- Little to no rain is expected over the next week, leading to
  worsening and expanding drought conditions.
&&
.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 252 AM CDT Mon Sep 8 2025
Very little has changed regarding the forecast for the next week,
with a warming trend on the way and very limited chances for much
needed rainfall.
While well above average temperatures aren`t far away, another day
of mild and slightly below average temperatures can be expected
today, with forecast temperatures expected to reach the mid 70s to
near 80 degrees during the afternoon. These temperatures, combined
with low humidity, light southerly winds, and only some passing high
clouds, should lead to another very pleasant day. This is the result
of the influence of a large area of high pressure across the eastern
CONUS, and this feature will continue to impact our local weather
for much of the work week.
Overnight, cool temperatures can be expected once again, although
perhaps a few degrees warmer than this morning thanks to a slight
increase in south to southeast winds. It certainly won`t be "windy"
by any stretch of the imagination, but we may hang on to just enough
of a breeze to slow down the development of the nocturnal inversion
slightly. Meanwhile, some shallow steam fog will be possible along
the main stem rivers again, although these breezes will likely limit
this as well. Otherwise, there is little else of note regarding
weather conditions over the next 24 hours.
BRC
&&
.LONG TERM...  (Tuesday Night through Sunday)
Issued at 252 AM CDT Mon Sep 8 2025
Over the course of the work week, an upper level ridge will steadily
build across the central U.S. and slowly move eastward, eventually
settling across the Mississippi River Valley by the weekend. The
combination of building upper level heights and weak southerly flow
will allow temperatures to warm significantly between Tuesday and
Thursday, and this warmth will persist through the weekend.
Ensemble guidance has consistently maintained narrow forecast
temperature spreads over the past couple days of model runs, with
median forecast surface temperatures reaching near 90 degrees from
Wednesday through the end of the weekend and beyond. This aligns
well with 850 mb temperature forecasts of between 18 and 20
degrees, which is somewhere between the 75th and 90th percentile
of climatology for this region. It should be noted, though, that
the operational NBM forecast remains one of the warmer
deterministic solutions among guidance, and roughly near the 75th
percentile on most days through the next week. These temperatures
have also trended very slightly warmer over the past couple of
days, and reaching near 95 degrees in some cases by the weekend.
This may be slightly aggressive, however, the message is largely
the same whether the afternoon temperature is 90 or 95 degrees. It
will be warmer than average for an extended period of time, but
the low humidity should prevent temperatures from causing
significant heat issues.
The more likely impact over the next week will be the worsening
and/or expansion of drought conditions. Not only will this pattern
continue to favor a lack of rainfall, but the persistent warmth,
sunny skies, and low humidity may also exacerbate conditions due to
increased evaporation. We do start to see some limited precipitation
chances return to the forecast early next week as the upper ridge
shows some signs of weakening, but confidence is very low that this
will put a meaningful dent in drought conditions.
BRC
&&
.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 457 AM CDT Mon Sep 8 2025
VFR conditions are expected throughout the 12Z TAF period with
persistent light southeast winds. Some patchy steam fog is
possible at the start and end of the period along the Missouri
and Mississippi Rivers, and brief visibility reductions have been
observed early this morning at SUS. However, this is not expected
to last long, and impacts should be limited to only the first hour
or so at the start of the 12Z TAF period.
BRC
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion