Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

968
FXUS63 KLSX 151123
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
623 AM CDT Sun Mar 15 2026

.KEY MESSAGES...

- There is a threat for isolated to scattered severe thunderstorms
  this afternoon across southeastern Missouri and southwestern
  Illinois. The primary threat is damaging wind gusts, with a
  secondary threat of tornadoes.

- Wind gusts as high as 45-50 mph are expected today through
  tonight. A Wind Advisory remains in effect.

- Minor snowfall is forecast late this evening and tonight, with accumulations
  of 1-3" forecast along and north of Hwy 36 and I-72 in
  northeastern Missouri and west-central Illinois.

- Unseasonable cold is expected Sunday night through Tuesday.


&&

.SHORT TERM... (Through Monday Night)
Issued at 244 AM CDT Sun Mar 15 2026

Early morning water vapor imagery shows an upper-level trough
digging southward over the western CONUS, with flow over the Middle
Mississippi Valley becoming increasingly southwesterly. A deepening
low can bee seen in surface observations over the Central Plains,
with a sharp cold front extending southward into the Southern
Plains. Through the day, this low and cold front will quickly drift
eastward, with the low`s center being directly north of the CWA and
the front entering the CWA around 18z. Within the warm sector, a
tight pressure gradient and strong low-level jet will lead to gusty
southerly surface winds. While gusts of 30-40 are the most
reasonable outcome, isolated occurrences of 45 mph or greater (Wind
Advisory criteria) are expected ahead of the front.

These winds will be transporting moisture northward, leading to
building instability ahead of the front as it passes through the CWA
this afternoon. Guidance is split into two camps: one where we fully
destabilize at the surface immediately ahead of the front, leading
to as much as 250-500 J/kg of SBCAPE, and one where surface-based
parcels remain mostly to completely capped. Either solution favors
convection begin tied to the fast moving front, leading to high
confidence in updrafts frequently being undercut and elevated. The
linear forcing from the front paired with the deep-layer shear
vectors have a parallel orientation will favor a linear storm mode.
Where cold pools can develop and localized surges occur, damaging
wind gusts will be a concern, as well as brief tornadoes given the
amount of shear. Given the degree of instability or lack thereof and
the concerns about the fast moving front, these severe weather
threats are expected to be isolated and primarily confined to far
southeastern Missouri and southwestern Illinois. If convection is
able to remain just ahead of the front and surface based and/or more
instability is realized than currently forecast, the threat for
severe thunderstorms will be more scattered across the SPC Day 1
Slight Risk.

In the wake of the front, winds will quickly shift to out of the
northwest and temperatures will plummet. The northwesterly winds will
remain elevated through the overnight hours with widespread 45-50
mph gusts expected. The most favorable area for gusts frequently
reaching this threshold is north of I-70, where the pressure
gradient is tighter and winds aloft stronger.

Mid-level frontogenesis will force a band of light precipitation in
the wake of the main front this evening into the early overnight
hours mainly across portions of Missouri. Thermal profiles aloft
favor this precipitation to be primarily snow that will have
increasing effectiveness at sticking as temperatures drop below
freezing. Snow chances will linger overnight across northeastern
Missouri and west-central Illinois as the deformation zone pivots
overhead. Surface temperatures will initially be above freezing with
pavement temperatures lagging slightly behind, limiting snow`s
ability to accumulate and produce impacts at first. The strong winds
will fracture dendrites, and shallow saturation within the dendritic
growth zone will limit SLR. All of these factors combined point to a
dusting of snowfall for most locations, with isolated pockets of 1-
3" across portions of central and northeastern Missouri as well as
west-central Illinois. Given the expected isolated nature of these
greater amounts and related impacts, a Winter Weather Advisory is
not being considered at this time.

With precipitation departing the CWA through the early morning hours
Monday, our attention turns to the anomalous, bitter cold that will
be moving into the region. Strong cold air advection will cause
temperatures to bottom out in the low 20s to teens, with the strong
winds producing wind chill values around 0 for most locations.
Temperatures will struggle to warm above freezing during the day
Monday despite clearing skies, with the NBM only having a 40-50%
chance of reaching 32 degrees for areas south of I-70. The clearing
skies and high pressure moving into the region will set the stage
for Monday night being the coldest point in the period, with
widespread teens and single digits expected for lows.

Elmore

&&

.LONG TERM... (Tuesday through Saturday)
Issued at 244 AM CDT Sun Mar 15 2026

On Tuesday, guidance consensus is that the axis of the aforementioned
upper-level trough will be pushing into New England, with
northwesterly flow persisting over much of the Midwest. Despite
this, low-level ridging will begin building into the Middle
Mississippi Valley, ushering in warmer temperatures aloft that will
correspond with surface temperatures moderating. However, given
Monday`s brutal cold, temperatures will not recover easily, with
ensemble means on Tuesday supporting temperatures still 15-20
degrees below seasonal normals.

Guidance consensus continues to depict a clipper quickly diving
southeastward through the Midwest Tuesday night into Wednesday
morning, though differences in the specific track and timing abound.
A majority of guidance has the clipper tracking just north of the
CWA, favoring the greater precipitation chances and amounts to be
well north of the CWA. Light precipitation will also have to fight
dry air over the CWA, with sufficient saturation for it reaching the
surface occurring briefly mainly for areas north of I-70.
Deterministic soundings support precipitation starting as snow
before transitioning to rain as the previously mentioned low-level
ridging continues to advect warm air into the region.

This clipper will only serve to slow our warming trend at most, with
nearly the entire global ensemble suite showing temperatures
continuing to trend upward through Friday as the CWA remains on the
eastern edge of deep ridging. Ensemble consensus breaks down
significantly next weekend on the handling of the eastern trough,
with a portion of guidance showing it deepening as a strong
shortwave digs into the East Coast. While these solutions keep the
core of the colder air east of the Middle Mississippi Valley, they
do provide a glancing blow of cold that could cut temperatures as
much as by 20 degrees per the 25th percentile of temperature
spreads. If this does not occur, then above normal temperatures will
continue through the weekend.

Elmore

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 622 AM CDT Sun Mar 15 2026

A potent system will bring a strong cold through the region late
this morning through this evening. High clouds are already
overhead as the front is extends north/south over eastern Kansas.
The primary issue will be increasing winds ahead of the front with
increasing thunderstorm potential from early afternoon through
this evening. KCOU/KJEF may avoid the convective nature of
activity as instability is limited. To the north, stratiform rain
is favored around KUIN. Each of these sites will drop to MVFR with
intermittent IFR possible this evening as colder temperatures move
in an lower cloud bases on the back side of the system.

Metro terminals will see the greatest potential for thunderstorms
as they become more organized and intensify along the cold front
this afternoon. This line poses a threat for damaging winds up to
70 mph (~60 kts) with the strongest thunderstorms. Tornadoes are
also possible, but the environment will be more favorable to the
southeast. Expect thunderstorms to last 1-2 hours before
stratiform rain continues behind the advancing line. MVFR/IFR
conditions are expected with LIFR possible in the heaviest
thunderstorms.

As the system pulls northeast, much colder air wraps into the
western side with chances for light snow. The best potential is at
KUIN, where some accumulations are likely. Central MO/metro sites
have lower chances, though a few hours of light snow is possible,
resulting minor visibility restrictions. Once snow ends,
conditions improve to VFR through Monday morning.

Maples

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Wind Advisory from 10 AM this morning to noon CDT Monday for
     Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-
     Franklin MO-Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis
     MO-Lincoln MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-
     Montgomery MO-Osage MO-Pike MO-Ralls MO-Reynolds MO-Saint
     Charles MO-Saint Francois MO-Saint Louis City MO-Saint
     Louis MO-Sainte Genevieve MO-Shelby MO-Warren MO-Washington
     MO.

IL...Wind Advisory from 10 AM this morning to noon CDT Monday for
     Adams IL-Bond IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-
     Greene IL-Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe
     IL-Montgomery IL-Pike IL-Randolph IL-Saint Clair IL-
     Washington IL.

&&

$$

WFO LSX