Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

432
FXUS63 KLSX 282035
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
235 PM CST Sat Feb 28 2026

.KEY MESSAGES...

- A quick round of rain/snow is expected (60-90%) late Sunday
  through early Monday. Minor accumulations are possible with
  uncertainty in the location of a narrow band of 1-2" of wet
  snow by early Monday morning.

- Multiple rounds of widespread rainfall are likely (>80%)
  Tuesday through the end of the week. A few thunderstorms may
  accompany rainfall at times.

&&

.SHORT TERM... (Through Sunday Afternoon)
Issued at 230 PM CST Sat Feb 28 2026

Regional surface analysis reveals a small and disorganized low
pressure system working its way eastward along a stationary front
that is draped from central Missouri into southern Illinois. Doppler
radar is picking up on an area of light precipitation coinciding
with low-mid level frontogenesis that is now working its way into
eastern Missouri. Throughout the day, this precipitation has had a
tough time reaching the surface with dry low-level air in place. In
fact, reports of light rain at the surface have been limited to
locations generally underneath the heavier reflectivity signatures.
As this system continues to progress eastward along the stationary
front, scattered and brief periods of light rain can be expected for
some locations mostly along and south of I-70 this afternoon into
the evening.

Locally isolated elevated fire weather conditions were expected
across the area today and that has become a reality for locations
generally across far northern Missouri and southern Missouri. For
these locations, the lack of cloud cover has allowed relative
humidity values to reach the 20s with some lower 20s across the
Ozarks and near Mark Twain Lake. Sustained winds have been on the
lighter side which has resulted in very localized pockets of
elevated fire weather despite a larger spatial extent of lower
relative humidity. Where the mid-level clouds have been persistent
this afternoon, generally along and south of I-70, relative
humidity values have bottomed out in the lower 30s and will likely
flatten out or even moderate a bit as mid-level clouds look to
remain across this area until later this afternoon.

Once the weak surface low treks off to the east later this evening,
it will drag a cold front southward across the region. More
seasonable air will move in behind the FROPA with strong low-level
cold air advection in place later tonight and into the day on
Sunday. As a result, highs on Sunday will be about 20 degrees colder
than today with afternoon temperatures in the low 40s north of I-70
and upper 40s to the south. With colder air in place across the
region, this will help to set the stage for the weather system that
is expected to begin impacting the region with wintry precipitation
and rain Sunday evening into Monday.

Peine/Maples

&&

.LONG TERM...(Sunday Evening through Next Saturday)
Issued at 230 PM CST Sat Feb 28 2026

The slight northwest to southeast lean in the mean upper flow
will draw an upper level shortwave across the region Sunday night
through early Monday. Working down through the mid-level layer, it
becomes apparent that return flow will become oriented to set up
south to southwesterly flow, drawing moisture northward around
the western side of a ridge centered over the southeastern CONUS.
Though moisture is initially lacking, it is enhanced by the
development of a nocturnal LLJ aimed at southern sections of
Missouri Sunday night. Sunday evening through Monday morning will
be the prime time for potential winter hazards.

As the disturbance approaches the Mid-Mississippi Valley, dry air
ahead of the system is quite deep, extending upward through 600mb.
Precipitation chances are introduced over central Missouri around or
just shortly before 00z Sunday evening. Deterministic model
soundings show the dry layer is overcome and ultimately becomes
deeply saturated within about 3 hours. Surface temperatures have a
more natural distribution from north to south and dewpoint
depressions of 15-20 degrees. This puts several factors into play
for winter hazards to materialize: 1) How quickly the air saturates
for precipitation to reach the surface. 2) As air saturates, how
much will surface temperatures cool by Monday morning and where will
the higher precipitation rates set up for most efficient wet bulbing?
3) Road temperatures are likely to be warm with a short period of
near-freezing temperatures bookended by warmer air. 4) Although the
corridor of the more intense precipitation has shifted north over
the last few runs, convergence at the nose of the LLJ is
concentrated over southern Missouri, spreading north up through I-70
before intensities decrease to the north.

Current thinking is the there will be about a 6 hour window for
rain/snow or wet snow to accumulate under the heaviest banding where
where convergence and lift coincide with higher precipitation rates.
With surface temperatures near or just above freezing, precipitation
rates and type (snow) will determine whether impact become realized.
Even so, the suite of deterministic guidance show the DGZ gradually
becomes unsaturated 06z-12z from west to east. While cloud ice is
lost, precipitation rates drop and the wet bulbing factor is less of
an influence as we climb out of our diurnal lull. Freezing
rain/drizzle would be the primary concern if not for the greater
sensitivity (versus snow) to surface/air temperatures. Given the lack
of a truly strong, shallow cold layer near the surface and warm air
advection, the transient nature of the airmass and moisture is more
likely to keep freezing drizzle/rain confined to elevated surfaces.
Plus, WAA cases are not great setups with enough persistence for ice
accumulation. Therefore, I`m skeptical of impacts directly related
to ice accumulation, though the threat is not necessarily zero.

The most likely outcome at this point is for a brief period of wet
snow or rain/snow mix with profile temperatures huddled near
freezing in the surface/mid-level layer. West/east frontal forcing
is maximized near or just south of I-70 with precipitation further
north into the cold air moreso supported by mid/upper ascent of the
shortwave. A narrow corridor of 1-2" could fall where all caveats
mentioned above are overcome. This does not seem to be a system with
widespread hazards given the transient nature, WAA, and already mild
ground surface temperatures. Latest HREF data is even less
impressive with hourly QPF rates of 0.01-0.05" along and south of I-
70, where snowfall rates are best positioned to overcome warmer road
temps. To get into even higher rates, one must travel even further
south into warmer air, where the nose of the LLJ is focused over
southern Missouri. RAP seems to be the farthest north in spreading
precipitation up through the MO/IA border, while other guidance
tracks precipitation east-southeastward along the slowly-advancing
warm front. Therefore, RAP trends, along with other guidance will
bear watching and small scale details are made out by hi-res
guidance.

Any snowfall is expected to melt quickly Monday with mild
temperatures continuing throughout the remainder of the week. The
main story will shifts to the potential for multiple rounds of
rainfall and an opportunity to improve on current drought conditions.
The late Sunday/Monday system briefly reinforces cooler air to the
south before returning northward as a warm front late Monday into
Tuesday. Zonal upper level flow introduces several shortwaves into
the center of the country through next week with ridging over the
southeast CONUS serving compliment each round with moisture. It
won`t be raining all week, but multiple waves are possible. Another
consideration is how an upcoming sudden stratospheric warming event
pans out in early March. At this time, a weaker lobe focuses over
southern Canada with troughing focused over the Intermountain West.
This would favor warmer than normal temperatures with deepening
southwesterly flow through the end of the period. Considering the
scenario, initial rainfall may not pose as much of a flood threat,
but as soil moisture increases and tributaries rise, rounds of
rainfall in the late week period will raise interest should
preceding event over-perform.

Peine/Maples

&&

.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1205 PM CST Sat Feb 28 2026

A weak low pressure system, currently over the Central Plains, will
push east into the area this afternoon. Ahead of this system,
current radar reflectivity unveils an area of light rain across
central and southern Missouri. Throughout the morning, upstream
observations have shown that where precip is reaching the ground,
under the heavier showers, ceilings (6-10kft) and visibilities
(10SM) both remain unaffected, due to the light nature of the
precipitation. These light rain showers have the best chance to
impact the central Missouri terminals over the next few hours with
the impact being a wet runway for a few hours. These showers have a
low chance (30%) to reach the STL metro terminals, with the best
chance between 20-22Z, while confidence is high that KUIN will
remain dry today.

Otherwise, VFR flight conditions are expected for the entire period.
Surface winds will be variable today as the low center progresses
over the area this afternoon. Later this afternoon into the evening,
a cold front drops in from the north leading to northerly winds into
tomorrow with increasing clouds ahead of the system set to impact
the region beginning Sunday evening.

Peine/Maples

&&

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

$$

WFO LSX