St. Peters, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

257
FXUS63 KLSX 030002
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
602 PM CST Mon Feb 2 2026

.KEY MESSAGES...

- There is a 20 to 40 percent chance of light freezing drizzle
  and light snow Tuesday morning in east-central, southeastern MO
  and southwestern IL. Only isolated impacts are expected with
  very light and localized accretions/accumulations.

- Varying temperatures are expected through the weekend with
  temperatures mostly above average after Wednesday. No
  precipitation is also forecast during that time.


&&

.SHORT TERM...  (Through Late Tuesday Night)
Issued at 249 PM CST Mon Feb 2 2026

Today is the warmest day in 1.5 weeks for most of the CWA with
temperatures warming into the mid-30s to mid-40s F, near 50 F to the
south of a stationary front in southeastern MO. The exception is
where stratus has lingered across much of IL, keeping temperatures
closer to the low-30s F. Most of tonight will be dry with
temperatures cooling into the 20s to near 30 F, beneath increasing
clouds ahead of an approaching upper-level shortwave trough.

Within upper-level northwesterly flow, a shortwave trough will pass
over the Mid-Mississippi River Valley Tuesday morning. Model
guidance varies slightly on when associated precipitation will begin
developing, but probabilities of measurable precipitation are much
higher to the east of the CWA (across the Ohio Valley). That being
said, HREF derived 6-hour probabilities of measurable precipitation
are still 20 to 40 percent across east-central, southeastern MO and
southwestern IL Tuesday morning. Confidence is high that any
precipitation that does fall will be very light and short-lived with
even the 90th percentile of QPF under 0.05". Precipitation would
likely be a variation of light freezing drizzle and light snow given
a 2 km-deep low-level layer of moisture, temperatures between -5 and
0 C, and weak ascent along with a period of potential seeder-feeder
mechanisms temporarily increasing the cloud ice. At this point,
confidence is low in impacts beyond isolated slick spots during the
morning commute with the precipitation being very light and only
highly localized ice accretion up to 0.01" and snow accumulation up
to 0.2" resulting. Clouds will decrease during the afternoon but low-
level CAA will only allow temperatures to warm into the 30s F,
except near 40 F in southeastern MO closer to the warm sector.

Pfahler

&&

.LONG TERM...  (Wednesday through Next Monday)
Issued at 249 PM CST Mon Feb 2 2026

The seasonably cool airmass will remain in place on Wednesday
beneath cyclonic flow within an overhead upper-level trough,
translating to high temperatures in the mid-20s to mid-30s F.
Thursday through the upcoming weekend, model guidance is in
agreement that upper-level flow will become northwesterly across the
Mid-Mississippi River Valley with multiple passing shortwave
troughs. Nearly 95 percent of ensemble model membership keeps the
CWA dry with the main impact of these troughs expected to be
associated periods of pronounced prefrontal low-level WAA and the
brunt of post-frontal airmasses passing to the northeast. NBM
interquartile temperature ranges increase to around 15 F by the
weekend with uncertainty in the exact timing and strength of one or
more passing cold fronts. There is still a signal for Friday to be
the warmest day of the work week, followed by varying degrees of
cooler temperatures over the weekend. Either way, even the 25h
percentile of temperatures remains at or above average Thursday
onward and certainly warmer than our previous stretch of cold
temperatures. The latest CPC temperature outlook and CIPS
temperature analogs also point to mild temperatures being dominant
beyond the 7-day forecast period.

Pfahler

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 601 PM CST Mon Feb 2 2026

A west to east oriented band of MVFR stratus that cleared KUIN in
the last hour is currently positioned over west-central Illinois as
it slowly drifts eastward. Model guidance is keying in on this MVFR
stratus advecting southward overnight, potentially impacting KUIN
again later this evening. A weather system is currently approaching
from the west with low-level moisture advection from the Gulf
ramping up tonight leading to lowering ceilings by the early
morning. The current expectation is that MVFR ceilings occur
tomorrow morning at both the St. Louis metro and central Missouri
terminals. There is still a 30% chance that tomorrow morning the St.
Louis metro terminals will receive a brief period of freezing
drizzle/light snow along with IFR ceilings and lowered visibilities.
Conditions across the region are expected to slowly improve through
the afternoon as the weather system departs to the east. Surface
winds will remain light and variable tonight with sustained
northeasterly winds returning tomorrow morning before turning more
northerly by tomorrow afternoon.

Peine/Elmore

&&

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

$$

WFO LSX