Chesterfield, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

546
FXUS63 KLSX 060321
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1021 PM CDT Fri Sep 5 2025

.KEY MESSAGES...

- Rain is likely across parts of southeast Missouri
  tonight...primarily late this evening and overnight. The chance
  for rain rapidly decreases farther north.

- Cool and dry weather is expected for Saturday and Sunday.
  Temperatures return to near normal Monday and Tuesday, then
  above normal for the remainder of the week.


&&

.SHORT TERM...  (Through Late Tonight)
Issued at 223 PM CDT Fri Sep 5 2025

Another mid/upper level short wave is moving southeast through South
Dakota around the stacked low pressure system over southeastern
Canada. The 850mb reflection of the wave will ride along a
baroclinic zone draped across southern Missouri tonight, and this
will be the primary forcing mechanism for rain. Short range guidance
is showing moderately strong moisture convergence developing this
evening ahead of the 850mb wave as a weak low level jet intersects
the baroclinic zone over Missouri.  This results in varying amounts
of precipitation across mainly southern Missouri with some models
showing light rain as far north as the I-70 corridor.  However, high
pressure over the Great Plains and Upper Midwest is pushing
cooler/drier air into the Mid Mississippi Valley.  This dry low
level air is what`s eating into the precipitation currently showing
up on RADAR.  While some light rain/sprinkles have been reaching the
ground in Missouri, most reports have been a trace so far, with only
a couple of measured 0.01 inch.  RAP forecast soundings are not
optimistic for much measurable precipitation north of the Eastern
Ozarks in our forecast area tonight due to the dry air which will
continue to be pushed into the area from the north.  However, the
low levels do moisten up enough over our eastern Ozarks counties
that I do think measurable rain is likely (60-70%), mainly after 04-
05Z when the forcing will be strongest.  Rain should move southeast
of our area by 12Z Saturday as the 850mb front is pushed farther
south.

Carney

&&

.LONG TERM...  (Saturday through Next Friday)
Issued at 223 PM CDT Fri Sep 5 2025

The remainder of the forecast is dry and relatively uneventful
with a sprawling surface high dominating the weather at least
through Tuesday/Wednesday. Cool dry air brought into the Mid
Mississippi Valley by the high will slowly moderate from 8-10
degrees below normal in the mid to upper 70s on Saturday and
Sunday, to near and slightly above normal in the upper 70s to the
mid 80s on Monday and Tuesday. Medium range deterministic and
ensemble guidance continues to show a strong upper level ridge
building across the Central U.S. from the middle to the end of the
week. The deterministic NBM continues to advertise highs around
90 under the ridge which is still near the 75th percentile for
highs on the LREF. However the NBM`s temperature forecast has been
consistent, and fits the upper level pattern well, so I will
continue to go with them.

Carney

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1005 PM CDT Fri Sep 5 2025

Unimpactful light rain will continue through tonight for portions
of southeast Missouri and southwest Illinois. In central Missouri,
residual rain paired with clear skies, light winds, and cool
temperatures should result in patchy radiational and steam fog.
Therefore, I`ve added MVFR vsbys at KCOU and MVFR to IFR at KJEF
given it`s received more rain and is susceptible to steam fog.
Further east, clouds are forecast to clear quickly enough for
patchy MVFR to IFR steam fog to develop as far east at KSUS. Any
fog that does develop will burn off quickly after sunrise. Aside
from that, VFR conditions are forecast through the TAF period.


Jaja

&&

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

$$

WFO LSX