Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

204
FXUS63 KLSX 140742
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
242 AM CDT Sat Mar 14 2026

.KEY MESSAGES...

- Showers and thunderstorms are forecast Sunday afternoon and
  early evening. There is a low chance that a few storms become
  capable of primarily damaging wind gusts and secondarily
  tornadoes across far southeastern Missouri and southern
  Illinois.

- Strong non-thunderstorm winds are expected through the day
  Sunday into Sunday night when they will peak. Then, the chance for
  gusts reaching and exceeding 45 mph is greatest (90%) north of
  I-70.

- Plummeting temperatures Sunday night will lead to rain changing
  to snow, with a 40-50% chance of minor impacts across
  northeastern Missouri.


&&

.SHORT TERM... (Through Sunday Night)
Issued at 241 AM CDT Sat Mar 14 2026

With the number and magnitude of impacts forecast for Sunday and
relatively calm weather today, the short term discussion will focus
solely on Sunday.

Through the early morning hours Sunday, an upper-level trough will
rapidly dig equatorward over the central CONUS as a surface low
deepens over the Central Plains. This will strengthen an expansive
low-level jet that will stretch from the Southern Plains
northeastward toward New England, pairing with a tight pressure
gradient at the surface to produce gusty southerly winds starting
Sunday morning. Probabilities from the 00z HREF for 45+ mph gusts
(Wind Advisory criteria) top out as high as 90% over IL during the
morning and early afternoon. However, my confidence is not as high,
as the southerly direction of the winds is unfavorable for advisory
criteria per local climatology, and it has been historically
difficult for our CWA to reach criteria while in the warm sector.
Gusts of up to 35-40 mph are a more reasonable solution.

At the very least, these winds will feed moisture into the region
ahead of a fast moving, strong cold front. The degree of moisture
return will be crucial for severe thunderstorm chances. Recent
guidance trends favor 1) a faster front and/or very little to no
surface-based instability materializing over the CWA, and 2) greater
capping and a stronger warm nose in the low to mid-levels thanks to
robust warm air advection. Shear will be ample, with guidance
consensus favoring approximately 60 kts of 0-6 km bulk shear - more
than enough for organized convection. The shear vectors` nearly
parallel orientation to the front, which will be the main forcing
mechanism, supporting a linear storm mode. Given all of this, a
reasonable higher-end solution is that storms ramp up as they depart
the CWA, favoring an isolated to scattered severe thunderstorm
threat over far southeastern Missouri and far south-central Illinois
during the afternoon and early evening - deeper into the SPC Day 2
Enhanced Risk. If this occurs, damaging wind gusts would be the main
threat, with a secondary threat for tornadoes on the northern
portion of any bowing segments. Confidence is very low right now
that a severe threat will materialize as far west as the St. Louis
metro area.

Winds will quickly shift to the northwest with the FROPA and
strengthen during the early overnight hours and gust through Monday
morning. This is when the CWA, particularly areas north of I-70,
have the greatest chance (80-90% per the 01z NBM) of seeing gusts
over 45 mph. These probabilities seem reasonable, as the prevailing
direction and post-frontal placement are more favorable for the CWA
reaching Wind Advisory criteria historically. Given the lead time,
headline decisions will be put off for now, with a determination
being made within the next 24 hours once details can be fine-tuned.

These northwesterly winds will mark the beginning of a dramatic drop
in temperatures behind the front. Model soundings show the entire
lower atmosphere dropping below freezing rapidly, supporting a
change over from rain to snow as the front departs the CWA and the
deformation zone pivots into the region Sunday night. This is tricky
snowfall forecast, as mitigating factors to accumulating snowfall
and SLR will be initially above freezing pavement temperatures,
shallow moisture in the dendritic growth zone (DGZ), and gusty winds
fracturing ice crystals as they fall. Brief periods of instability
and an isothermal layer within the DGZ favor greater SLRs, with
guidance varying greatly in all factors from source to source and
run to run. While confidence remains high (70-90% per the 01z NBM)
in at least a dusting of snow on grassy and elevated surfaces,
confidence is lower in accumulations that produce widespread
impacts. If snow is able to accumulate enough to produce notable
impacts, northeastern Missouri is the most favorable portion of the
CWA. Even with minor accumulations, gusty northwesterly winds would
cause snow to blow around, leading to slick spots on roadways mainly
north of I-70 where the WPC WSSI-P has at least a 20% chance of
minor impacts, topping out as much as 50% across northeastern
Missouri. Snowfall rates will gradually wane late Sunday night
through very early Monday morning as temperatures continue to free-
fall into the teens and twenties for lows.

Elmore

&&

.LONG TERM...  (Sunday Night through Friday)
Issued at 241 AM CDT Sat Mar 14 2026

Early Monday, guidance consensus is that the axis of the upper-level
trough will be over the Middle Mississippi Valley, with flow through
the depth of the atmosphere becoming increasingly northwesterly
through the day. With the surface low moving through the Great Lakes
and a very cold, dry air mass advecting into the region, the lower
atmosphere is expected to dry out during the morning. Guidance that
has a faster low and more aggressive drying of the lower atmosphere
supports snow ending for areas north of I-70 as early as sunrise
Monday, while slower guidance would lead to an exit of the snow
chances closer to noon. The main story will be the cold, however,
with strong cold air advection and cloud cover notably muting the
diurnal curve. Confidence remains high in temperatures failing to
warm above freezing for most locations on Monday thanks to narrow
ensemble spread. NBM probabilities of highs remaining below 32 top
out at 80%+ along and north of I-70, with the same threshold having
a 60-70% chance of failing to be topped south of that corridor. This
will set the stage for relatively bitter cold Monday night, though
how cold remains slightly uncertain. High pressure moving into the
region will allow for winds to weaken and skies to clear, but how
quickly that happens and allows for radiative cooling varies among
guidance. Regardless, the 75th percentile of ensemble guidance
Monday night is colder than the 25th percentile for Sunday night`s
lows, leading to high confidence in this being the coldest point of
the period.

While both deterministic guidance and ensemble clusters show
northwesterly flow holding over the Middle Mississippi Valley
through the remainder of the period, the consensus is also for the
trough to shift eastward and deamplify. This will allow for low-
level riding to build into the region as soon as Tuesday, with
southerly winds returning to the area. As a result, temperatures
will begin moderating on Tuesday and return to more seasonable
values on Wednesday per ensemble means. A clipper will quickly scoot
through the Midwest late Tuesday into Wednesday, providing a chance
(40%) for a glancing blow of light precipitation late Tuesday night
into early Wednesday morning. Low-level winds with this clipper will
briefly turn northwesterly for Wednesday, but they will be weak and
cold air advection meager, having a negligible impact to
temperatures and the warming trend that will continue through the
end of the workweek.

Elmore

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1211 AM CDT Sat Mar 14 2026

VFR flight conditions will prevail at all local terminals through
the forecast period. Winds will strengthen through the late
morning and remain elevated through the remainder of the period.

Elmore

&&

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

$$

WFO LSX