Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

906
FXUS63 KLSX 271139
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
539 AM CST Sat Dec 27 2025

.KEY MESSAGES...

- Dense fog will persist across most of the forecast area through
mid-morning.

- A strong cold front will move through the area Sunday bringing a
marginal risk for severe thunderstorms followed by a strong but
brief Arctic airmass that will drop temperatures 40 degrees for
Monday.


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 333 AM CST Sat Dec 27 2025

Fog and low stratus continue to plague the forecast area this
morning, with many areas reporting 1/4 to 1/2 mile visibility. The
Dense Fog Advisory will remain in effect through mid-morning. As
daytime heating and low-level warm air advection kicks up fog is
expected to dissipate, and the stratus is expected to lift and
scatter through the morning. Highs today will once again peak in the
60s to low 70s across the area, with the coolest temperatures in
northeast Missouri and west-central Illinois where low clouds are
likely to linger the longest.

There is a 15-30% chance for showers tonight mainly along and north
of I-70 along a northward moving warm front associated with the
incoming system. There is a 15-20% chance for elevated thunderstorms
to develop within the overrunning precipitation late Saturday night,
though the risk for these to develop into severe thunderstorms is
low due to their elevated nature.

Delia

&&

.LONG TERM...  (Sunday Night through Friday)
Issued at 333 AM CST Sat Dec 27 2025

Sunday remains on track with a strong and dynamic cold front
dropping southeastward through the forecast area. There remains a 20-
50% chance for showers and thunderstorms to develop ahead of the
front Sunday morning, though the main concern for severe weather
remains along the front. The past 24 hours have seen changes in the
overall structure and timing of the system, mainly that the mid and
upper level support is now more closely tied to the surface front,
and that the whole system moves through the forecast area roughly 3
hours earlier than this time yesterday. Both are working to increase
confidence in the potential for severe weather along the front as it
moves through, though caveats still exist.

The amount of instability remains a major source of uncertainty,
with some guidance sources showing less than 100 J/kg of SBCAPE due
to weak low-level lapse rates. This would result in a severely
limited severe weather potential across our forecast area. Other
sources indicate 300-800 J/kg of SBCAPE ahead of the front, which
would result in a greater confidence in severe weather occurrence.
The greater the SBCAPE, the greater the potential for higher impact
severe weather. What is consistent across guidance sources,
regardless of the magnitude of the instability, is that any
instability that forms will initially surge northward from Arkansas
into Missouri and Illinois in the morning before being squeezed by
the front to the northwest and warming mid-levels to the southeast.
This will result in a narrowing corridor of conditions favorable for
severe weather during the late morning and through the afternoon.

The potential for ongoing showers and thunderstorms Sunday morning
may limit our ability to destabilize. But if instability is able to
grow larger than roughly 200-300 J/kg, over 50 kts of 0-6km shear
will be available to organize any thunderstorms that develop into
severe thunderstorms. With this shear parallel to the front, a
linear system is favored and damaging winds and quickly developing
tornadoes are the main concerns with severe portions of the line.

The front will exit the forecast area Sunday evening, though
precipitation will linger behind the front until the bulk of the dry
Arctic airmass barrels into the region overnight. This airmass will
help to push precipitation out of the forecast area, but the overlap
in precipitation and sufficiently cold air will be minimal if any.
So while a few snowflakes are possible as precipitation comes to an
end Sunday night, widespread snow is not expected.

The robust mid-level trough driving Sunday`s system will bring very
cold air to the region for Monday, dropping high temperatures nearly
40 degrees compared to Sunday. Windy conditions from a tight surface
pressure gradient will make it feel even colder, with wind chill
values struggling to make it out of the teens. Portions of northeast
Missouri and west-central Illinois will see wind chills remain in
the single digits during Monday afternoon. Thankfully this frigid
airmass will not linger, by Tuesday a low-level ridge will build in
to the west and increase warm air advection into the region. The
Arctic airmass will shift eastward and temperatures will moderate to
near normal by Wednesday. Another cold front is expected to drop
through the forecast area Thursday, though this front will be weaker
than Sunday`s with nearly no moisture associated with it.
Uncertainty still remains in how far south the front pushes, as well
as the strength of the surge of cold Canadian air into the mid-
Mississippi Valley. This results in a 15-20 degree spread of high
temperatures through the end of period. Despite this, confidence is
growing that temperatures will remain at or below seasonal normals
as the 75th percentile for high temperatures is near normal through
Friday.

Delia

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 530 AM CST Sat Dec 27 2025

Dense fog and low stratus continue to encompass the region,
impacting all terminals. Fog is expected to lift above 1/4-1/2
miles by mid-morning when the ongoing Dense Fog Advisory will
expire, though visibility reductions are expected to linger into
the late morning. IFR to MVFR ceilings will also linger through
much of the day. Confidence is low when the stratus deck will
exit the area, and there is a 50-70% chance that it will stick
around through the entire TAF period, particularly east of the
Mississippi River (including KUIN and KCPS).

Winds are becoming southeasterly to southerly this morning and
will become southwesterly by Sunday morning, picking up in speed
ahead of an approaching cold front that will bring showers,
thunderstorms, and gusty winds to the region beyond the current
TAF period.

Delia

&&

.CLIMATE...
Issued at 220 PM CST Fri Dec 26 2025

Well above normal temperatures continue. Record high temperatures
are within reach through Sunday. Daily record highs for each site
are listed below.

 St Louis    Columbia    Quincy
12/26   70(1942)    69(1942)    63(1942)
12/27   72(1971)    71(1946)    70(1946)
12/28   75(1928)    71(1984)    70(1984)

The all time December record highs are listed below.

St Louis - 76 most recently on Dec 3, 2021
Columbia - 76 most recently on Dec 15, 2021
Quincy - 75 on Dec 15, 2021


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Dense Fog Advisory until 9 AM CST this morning 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...Dense Fog Advisory until 9 AM CST this morning for Adams IL-
     Brown IL-Calhoun IL-Clinton IL-Jersey IL-Madison IL-Monroe
     IL-Pike IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX