Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

511
FXUS63 KLSX 212348
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
548 PM CST Sat Feb 21 2026

.KEY MESSAGES...

- Temperatures will be well below normal through early Tuesday.
  The colder air centers on Monday morning, when wind chills
  range from -5 to 5 (F).

- Rain chances (30-40%) are limited to a quick-moving system that
  arrives Thursday. Temperatures rise above normal through late
  week, staving off concerns of wintry precipitation at this time.


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 240 PM CST Sat Feb 21 2026

Upper height patterns show troughing is expected to broaden and
deepen just off the northeast coastline by Sunday. Ridge
amplification to the west will place the Mississippi Valley in
strong northwesterly flow. During this evolution, multiple lobes of
vorticity rotate southeastward down the western side of the trough
and over the mid-Mississippi Valley.

RAP guidance shows the first shortwave over northern Illinois,
exiting the area as it moves into the southern territory of the
Great Lakes. Two additional lobes move overhead over the next 36
hours. The first arrives late this evening/overnight and second
coming Sunday afternoon/evening. Fortunately, both will be
relatively inconsequential as an inverted surface ridge extends
southward through the eastern Plains and begins to slowly build
eastward. RAP soundings show a very thin veil (~25-50MB) of
saturation centered around 850MB hugging the Mississippi River.
Moisture depth increases to around 100MB on the Illinois side of the
river. Considering the northwest/southeast orientation of the
pattern, the Mississippi River serves as a rough demarcation between
mostly clear skies to the south/west and partly/mostly cloudy skies
to the north/east this weekend.

Dry conditions and below normal temperatures are expected through
the period. Concerns are limited to the extent of cloud cover and
pressure gradient wind gusts as the Great Lakes system rotates into
the Ohio Valley. This setup supports the persistence of cold air
advection through Monday as each vort lobe acts as somewhat of a
reinforcement to the cold airmass, pulling -15C (850MB) air
southward into the Tennessee Valley. Locally, -10C to -18C air
remains locked in from central Missouri through Illinois,
respectively. The brunt of the coldest air arrives late Sunday into
Monday morning. Pressure gradient gusts of 20-25 knots appear late
this evening into tonight and persist through early Monday morning
before the gradient shifts eastward. When combined with low
temperatures Sunday and Monday morning, wind chills bottom out
between 0-15 degrees (F) Sunday morning and -5 to 5 (F) Monday
morning. While not cold weather headline worthy, proper attire
should be considered, if outdoors for an extended period of time.

Temperature will be well below normal with morning lows ranging
through the teens/low-20s. High temperatures range from the upper
20s to mid-30s.


Maples

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 240 PM CST Sat Feb 21 2026

The week starts off quite chilly with well below normal temperatures
extending through Monday as the inverted surface ridge undergoes an
evolution to two separate surface highs (north and south) by late
Monday. Much of the day is spent solidly in northwest flow, though
mid-level temperatures begin to warm slightly. This precedes what
looks to be greater promise for warming temperatures through the
remainder of the week.

Despite the fact that upper ridge to the west loses amplitude
Tuesday, it`s the surface/mid-level features that exhibit greater
influence on the mid-Mississippi Valley. A mid-level low just north
of the U.S./Canadian border extends as far south as the mid-
Mississippi Valley, increasing west-southwesterly pressure gradient
flow. Meanwhile, the surface ridge strengthen and broaden over the
Gulf State/Northern Gulf. Southerly return flow sets up early
Tuesday, eventually turning southwest by late in the day. Sub-
freezing mid-level temperature are evacuated to the east, climbing
to 4-7C during peak diurnal heating Tuesday afternoon. Considering
that mean flow turns from westerly to west-northwesterly from the
mid to upper levels, warmer air makes more of a modest attempt to
return northward. The most notable warming will come Tuesday with
high temperatures 15-20 degrees warmer than Monday. High return to
the upper 40s/low-50s (IL) to near 60 degrees east/northeast of the
Ozark Plateau.

The NBM remains tightly clustered through Tuesday (3-5 degrees), but
begins to spread Wednesday and the spread continues to increase
thereafter. By Wednesday, yet another mid-level shortwave and
surface low quickly track across the center of the U.S. on a
southeast trajectory toward the Midwest. The speed and position of
this feature has the potential to creating a north/south disparity
in temperatures with LREF diagnostics showing 8-12 degrees between
the IQR. The greatest uncertainty line up along and north of I-70,
where the reinforcing cold front arrives a little quicker. Median
temperatures still land near to above normal with low-60s covering
southeast Missouri and low-to-mid-50s extending along and north of I-
70. Should the system speed up/slow down, temperatures will respond
in kind with cool/warmer temperatures, respectively.

The aforementioned temperatures scenario Wednesday runs ahead of the
weeks only precipitation potential and consequently the week`s only
real cool down. IQR spreads are roughly cut in half as the front
progresses to the southeast of the CWA. This will be more of a short-
lived nuisance with temperatures cooling by around 10 degrees
Thursday. Another consideration is just how much rain potential
there is given the speed and limited moisture return. Dewpoints
climb to around 50 degree up through I-70 with the greatest moisture
depth remaining over the Bootheel of Missouri into southern
Illinois. Therefore, what short-live lift is provided by the fast-
moving clipper, will provide a limited, short duration potential.
LREF probs highlight this well with <30% chance for measurable
rainfall along and north of I-44 and I-70 (IL). Probabilities don`t
climb much higher across the southeastern portion of the CWA,
peaking at 35%. Suffice to say, spreads at this distance are likely
smearing PoPs too broadly with differences in the speed/time of the
clipper.

Beyond Thursday, warmer temperatures are favored with fairly tight
cluster on Friday suggesting widespread 60s, possibly a few low-70s.
However, certainty is very low heading into next weekend with
multiple systems crossing the northern U.S. This brings the
potential for additional reinforcing fronts. Their position and
timing is far from certain at this distance in time. NBM spreads
have been rather impressive with 30-35 degrees of separation between
the upper/lower quartiles in the prior release of data. The latest
shows 20-25 degrees of spread, which may signal a better grasp on
specifics with time. The general characteristic is for cooling
temperatures with 50th percentile near seasonal norms.


Maples

&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 548 PM CST Sat Feb 21 2026

Dry and largely VFR flight conditions are expected through the TAF
period, with the exception of a period of MVFR ceilings Sunday
morning. These ceilings are most likely at KUIN with lower
confidence in them occurring at the rest of the terminals.
Northwesterly winds will briefly become light this evening, but they
will increase overnight into the day Sunday, occasionally gusting 22
to 30 kt.

Pfahler

&&

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

$$

WFO LSX