Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

070
FXUS63 KLSX 011126
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
526 AM CST Sun Mar 1 2026

.KEY MESSAGES...

- Wintry precipitation is expected along/north of I-70 tonight.
  Most locations will see no impacts, but there is the potential
  for a narrow swath of 2 to 4" of snowfall to cause minor travel
  impacts. It is uncertain where this heavier snowfall will be.

- There will be a series of opportunities for showers and some
  thunderstorms across the area Monday night through the end of
  the week. With above average temperatures, the chance of
  additional wintry precipitation is virtually zero.


&&

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 329 AM CST Sun Mar 1 2026

Low-level northerly CAA has cooled temperatures into the 20s and 30s
F this morning. With this cooler airmass, high temperatures today
will be around 15 to 25 F cooler than Saturday and mainly in the 40s
F as some patchy stratocumulus arrive and upper-level clouds
overspread the region ahead of an approaching upper-level shortwave
trough.

The aforementioned shortwave trough will aid in the development of
rain across eastern KS and western MO through midday/afternoon as
low-level WAA and isentropic ascent increases along a LLJ. This area
of precipitation will shift eastward into the CWA between 21z and
03z this evening as the parent forcing also translates eastward.
With a dry antecedent airmass, temperatures initially in the 40s F
are expected to quickly evaporatively cool/wetbulb into the 30s F
since precipitation will be persistent and rates will be increasing.

There is still a great deal of nuance to the subsequent
precipitation forecast tonight with questions in how much of the
area sees sufficient cooling of temperatures to see wintry
precipitation and what will the influence of a warm nose have on
precipitation type. Currently, the expectation for most locations
along/north of I-70 is that light rain will transition to a mixture
of wet snow and some sleet after onset. With warm ground
temperatures and air temperatures only marginally supportive of
accumulating snow (31 to 34 F), most areas should see only up to an
inch of snowfall on grassy and elevated surfaces with no impacts.
However, there has been some increasing concern for a quasi-
stationary corridor of strong low to mid-level FGEN to support
strong omega in the DGZ and snowfall rates high enough to overcome
melting and accumulate on roadways with minor impacts. It is not
completely clear where this narrow swath of heavier snow will be,
but the HREF LPMM of total snowfall and highest probabilities of
1"/hour rates highlight somewhere in northeastern MO toward the
east/southeast just north of I-70 in IL (perhaps near the St. Louis
metro) between 03 and 09z Monday. For this reason, a Winter Weather
Advisory has been issued for locally 2 to 4" of snowfall, but
impacts will be a much smaller subset of the advisory area.
Fortunately, any impacts will likely be limited to the time of
heaviest snow with temperatures warming slightly once rates decrease
and a strengthening warm nose favoring a transition back to rain
from south to north early Monday morning. Moisture will become more
shallow by sunrise Monday with some patch drizzle possibly
lingering. Isolated pocket of freezing drizzle cannot be ruled out
across northeastern MO and west-central/south-central IL, but
confidence is not high that it will be impactful.

After around 15z, most of the daytime Monday is anticipated to be
dry with widespread clouds limiting warming of temperatures to the
40s F in many areas amidst weak low-level WAA.

Pfahler

&&

.LONG TERM...  (Monday Night through Saturday)
Issued at 329 AM CST Sun Mar 1 2026

An overall wet and active weather pattern is evident this week
through the upcoming weekend as upper-level zonal flow transitions
to southwesterly flow across the central CONUS in response to
longwave troughing develops across over the Intermountain West.
Within this flow, a parade of shortwave troughs of varying amplitude
will traverse the Mid-Mississippi River Valley atop anomalous Gulf
of Mexico moisture streaming northward providing a series of
opportunities for showers and even some thunderstorms beginning as
early as Monday night. In fact, global ensemble model 24-hour
probabilities of measurable rainfall do not fall below 60 percent
anywhere in the CWA through Saturday, meaning it is unlikely that
the area goes more than 24 hours without seeing rainfall in this
period. The probabilities of 2"+ total rainfall are 50 to 80 percent
across the entire CWA through the next 7 days, which would help
substantial improve drought conditions. Above average temperatures
keep the chance of additional wintry precipitation virtually zero
and the NBM interquartile range of high temperatures generally
varies between the 60s and 70s F Tuesday onward.

The threats of flash flooding and severe thunderstorms are non-zero
in this pattern, but these threats will rely on smaller scale
details including the timing and amplitude of individual shortwave
troughs and the position/orientation of effective fronts and
boundaries permitting higher instability to extend northward into
the CWA. These details vary among global model guidance and likely
will not be better resolved until lead time further decreases.

Pfahler

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 526 AM CST Sun Mar 1 2026

Dry and VFR flight conditions will likely persist into the afternoon
across the area. There are some MVFR ceilings upstream to the
northeast of the region, but model guidance unanimously scatters
these ceilings after sunrise before reaching any of the terminals. A
weather system will bring widespread precipitation and MVFR to IFR
flight conditions to the region this evening through overnight with
generally rain south of I-70 and wintry precipitation along/north of
I-70. Therefore, snow is most likely at KUIN and rain is most likely
at KCOU and KJEF. However, at St. Louis metro terminals, the
precipitation type is more uncertain and could vary with time
between rain, snow, and even some sleet. There is potential for a
narrow corridor of 2 to 4" of snowfall, but it is uncertain if any
terminals will be directly impacted. Precipitation will end early
Monday morning, but there is a low chance that some patchy drizzle
lingers. Northeasterly winds this morning will gradually veer to
easterly tonight.

Pfahler

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Monday for Audrain MO-Knox MO-Lewis MO-Lincoln MO-Marion MO-
     Monroe MO-Montgomery MO-Pike MO-Ralls MO-Saint Charles MO-
     Saint Louis City MO-Saint Louis MO-Shelby MO-Warren MO.

IL...Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Monday for Adams IL-Calhoun IL-Greene IL-Jersey IL-Macoupin
     IL-Madison IL-Pike IL.

&&

$$

WFO LSX