Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

361
FXUS63 KLSX 212053
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
253 PM CST Wed Jan 21 2026

.KEY MESSAGES...

- Confidence in accumulating snowfall and impacts continues to
  increase for areas roughly along and south of I-70, including
  the St. Louis metro, for Saturday into Sunday. The Winter Storm
  Watch has been expanded to include this area.

- Bitter to potentially dangerous cold is expected Friday through
  at least Saturday.


&&

.SHORT TERM...  (Through Late Thursday Night)
Issued at 250 PM CST Wed Jan 21 2026

An abundance of solar insolation has aided in a nice warmup today as
the current temperatures range from the upper 30s to the north with
even some low 50s across the southeastern CWA. The latest surface
analysis reveals a cold front currently draped across Iowa that
gradually tapers off to the southwest into Kansas. This cold front
will continue to push southeast reaching northern Missouri later
this evening and the STL metro around midnight. The front will bring
a wind shift from southwest to northwest along with some
intermittent gusts to 20-25kts that will be confined to areas north
of I-70. A weak surface high slides in behind the front from the
west resulting in calm winds later tonight that will stick around
until tomorrow afternoon. This will lead to good radiational cooling
after midnight, allowing temperatures to reach the upper teens to
lower 20s by sunrise tomorrow.

On Thursday, cooler morning lows and increasing upper-level clouds
will result in a cooler day than what we had today, with highs
reaching the mid 30s to lower 40s. By Thursday evening, a very
strong Arctic front will be knocking on our doorstep as it quickly
pushes southward from the Northern Plains. Current indications are
that this Arctic front will push through the region sometime around
midnight Thursday night with the much colder air and stronger winds
lagging behind the northerly wind shift by a few hours. Plenty of
mid to low-level dry air will be in place ahead of and behind the
Arctic front, resulting in no precipitation chances with this
frontal passage. Once the Arctic air arrives, temperatures will fall
rapidly, so much that temperatures in northern Missouri will likely
be near or below zero by sunrise on Friday. The remainder of the
area will be in the single digits and teens by that time on Friday
as well, setting the stage for this weekends winter storm.

Peine/Elmore

&&

.LONG TERM...  (Friday through Next Wednesday)
Issued at 250 PM CST Wed Jan 21 2026

At the start of the extended period, our expected Arctic air mass
will be well on its way southward and becoming further entrenched
over the Midwest beneath a very broad upper-level trough. Through
the day, our eyes will be set on two shortwaves: one digging
southward along the west coast, the other spinning as a cutoff the
California Baja. How exactly these two shortwaves phase together
over the Southwest on Saturday has major implications on how our
winter weather will play out this weekend. An initial surface system
is set to pass through the South during the day on Saturday,
followed by a second on Sunday. The phasing of the shortwaves will
impact the track of the surface systems and their strength as they
move through.

The GFS/GEFS has recently begun trending slightly northward to
converge with the solutions that the ECMWF/ENS and Canadian/GEPS
have been stubbornly holding to over the last several days. At this
point, confidence is high that at least some accumulating snowfall
will occur over much of the CWA - it`s just a matter of how much.
Snowfall will initially have to contend a very dry near-surface
layer that will cause snowfall to struggle northward on Saturday.
However, continuous moistening of the lower atmosphere from the
south and an impressive dynamics are expected to overcome this dry
air, particularly over southeastern Missouri where an earlier onset
of snowfall is expected on Saturday. Snowfall is expected to
gradually encompass the rest of the CWA through the day as the
initial system passes directly to the south of the region. There may
be a brief lull in snowfall (or more intense snowfall) Saturday
evening and overnight; though, how much of a lull depends on the
phasing of the shortwaves. This second round early Sunday has the an
increasing probability to be more potent that the first as another
shortwave converges with the first over the center of the CONUS,
with the potential for coupling upper-level jet streaks leading to a
rapidly deepening surface low as it moves east of the region.
Guidance consensus is that snowfall will wane of the CWA through
Sunday afternoon and evening as the lift from the shortwaves shifts
eastward.

Now for snowfall totals. The longevity and potential intensity of
snowfall leads to a relatively high ceiling for snowfall totals,
particularly over southeastern Missouri, while a more southerly
track and stronger dry air would lead to a more mild event. Our
confidence in the latter is decreasing, as the aforementioned model
trends support a more northerly track. Deterministic soundings at
times show a deep isothermal layer located within the dendritic
growth zone from Farmington, MO and surrounding areas and as far
north as the St. Louis metro and I-70 corridor. Even with meager
forcing and lift, this would support intense snowfall rates at times
reaching 1"/hr. The result would be as much as 8", if not more, of
snowfall for portions of southeastern MO and as much as around 5"
for the I-70 corridor. These amounts are best estimates, with the
spread between the 10th and 90th percentiles from the 13z NBM being
as much as 10-12" across much of the CWA. Regardless, where snow
does fall, surface and ground temperatures well below freezing will
allow for accumulation to readily form on all surfaces, and impacts
to travel are expected. Where confidence is greatest in accumulation
and impacts (50% or higher), the Winter Storm Watch has been
expanded. This includes the St. Louis metro area.

Speaking of below freezing temperatures, the potency of this Arctic
air mass is notable and dangerous, despite it seemingly receiving
lesser attention than the snowfall. As of now, the coldest
temperatures are expected Friday through Saturday night as the
Arctic high bottoms out over the Midwest. Highs during this stretch
will struggle to get out of the single digits for areas north of I-
70, with locations south of that corridor remaining in the teens.
Overnight lows will drop into the single digits, with portions of
northeastern Missouri and west-central Illinois seeing values below
0 Friday night. Coupled with persistent northerly winds, wind chills
will be at least around 0 for much of this stretch. Confidence is
medium in a Cold Weather Advisory being needed for portions of the
area at times this weekend, with headline decisions waiting until
confidence is higher in specific temperatures and wind speeds.
Temperatures Sunday into Monday may be too warm for areas that have
snowpack from Saturday and Sunday`s snowfall.

Given the extent of impacts expected this weekend, little attention
was given to next week, and the NBM will be left as is. Generally,
the Arctic air mass will shift eastward as the upper-level trough
weakens, allowing for temperatures to moderate gradually by some
degree early next week.

Elmore

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1142 AM CST Wed Jan 21 2026

VFR flight conditions will prevail for the entire period. Westerly
surface flow with weak intermittent gusts (20kts) will continue
today under a clear sky. A brief weakening of winds is expected to
occur after sunset for central Missouri and the STL metro before a
weak cold front approaches from the north early tonight. This front
will bring a round of gusty (20-25kts) northerly winds, which will
be more widespread across northern Missouri. Behind the front, winds
will weaken and back to a westerly direction by sunrise tomorrow as
a weak surface high slides into the area from the west. Upper-level
clouds will steadily be on the increase by tomorrow afternoon.

Peine/Elmore

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Storm Watch from late Friday night through Sunday morning
     for Cole MO-Crawford MO-Franklin MO-Gasconade MO-Iron MO-
     Jefferson MO-Madison MO-Moniteau MO-Osage MO-Reynolds MO-
     Saint Charles MO-Saint Francois MO-Saint Louis City MO-
     Saint Louis MO-Sainte Genevieve MO-Washington MO.

IL...Winter Storm Watch from late Friday night through Sunday morning
     for Bond IL-Clinton IL-Fayette IL-Madison IL-Marion IL-
     Monroe IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX