Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

430
FXUS63 KLSX 191732
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1132 AM CST Thu Feb 19 2026

.UPDATE...
Issued at 424 AM CST Thu Feb 19 2026

As moisture continues its push north this morning, it has begun to
encounter an area of previously cooled air. The resulting surface
moisture inversion has led to areas of dense fog developing
primarily along and just north of an area of stratus from
southeast Missouri into southern Illinois. This does include
portions of the St Louis metro area. We`ve issued a Dense Fog
Advisory until 9AM in areas currently affected and in areas that
may soon be affected.

Kimble

&&

.KEY MESSAGES...

- A few thunderstorms are expected across the region today with
  the potential for hail, damaging wind, and perhaps a tornado.

- Drier air moves in from the west this afternoon leading to a
  period of critical fire weather conditions. A Red Flag Warning
  is in effect for areas impacted by this.

- A cold front tonight brings our warm weather to an end, with
  colder weather lasting through the weekend and into early next
  week.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 257 AM CST Thu Feb 19 2026

Low pressure is emerging out of the lee of the Central Rockies into
Kansas this morning in response to a shortwave trough embedded in
fast WSW flow aloft. Ahead of the low a complex situation is still
evolving. We saw dry air push eastward across the region yesterday,
but moisture is already beginning to push northward. Dewpoints early
this morning have still been in the upper teens to low 20s in such
locations as Columbia, Hannibal, and Quincy. However, not too far to
the south dewpoints have risen into the mid to upper 50s as far
north as the outskirts of the St Louis metro. A warm front is
setting up at the northern edge of this moist advection with light
southerly winds in the moist sector and light easterly winds to the
north of it. Further north still a cold front has settled south
through Iowa, stalling just south of the Missouri border. Northeast
winds north of this boundary have begun a significant cool down with
subfreezing temperatures noted across much of Iowa. Further west, a
north-south oriented boundary is moving east through central Kansas
and western Oklahoma to the south of the surface low track. This
boundary serves as a pseudo-dry line, the boundary between moist air
to the east and considerably drier air to the west.

Low pressure is expected to move ENE today roughly along the stalled
frontal boundary through northern Missouri. Ahead of it moisture
initially surges northward before dry air pushes in from the west.
In the moist sector we will be setting up instability for the
potential for thunderstorms in an environment characterized by high
wind shear. High resolution guidance is keying in on initial
thunderstorm activity developing shortly after daybreak in central
Missouri, tracking east roughly along I-70 through the morning and
exiting into central/eastern Illinois by early afternoon. This
activity should be elevated in nature as the low levels remain
inverted. Thus while this activity will have access to strong mid
level winds for some storm organization, any severe weather threat
should be limited to marginally severe hail. Parameters for hail are
fairly weak considering the depth of instability is somewhat shallow
and does not have much access to cold air aloft.

The more significant severe weather threat is in the afternoon and
early evening when surface-based instability becomes more
accessible. In this environment, supercell thunderstorms with
damaging winds and tornadoes would become a greater threat. However,
looking at the latest high resolution guidance, few members develop
additional thunderstorms this afternoon and evening due in part to
weak forcing to trigger storms and the potential for a warm layer
aloft to cap the instability. Thus our confidence in this second
more significant round of thunderstorms affecting our area is lower
than it has been in previous days. That said, if thunderstorms do
form in this environment they will be in a prime environment to
produce severe weather. And it may be the case that the initial
morning activity attempts to become surface based as it exits our
forecast area around noon. So while our severe weather outlook
remains very similar to what it looked like the last few days, it`s
a threat that is conditional upon storms forming in the afternoon.

Meanwhile, the prefrontal trough serving as an effective dryline
will enter our area from the west this afternoon, abruptly dropping
dewpoints in a much deeper mixed low level environment downsloped
from the southern Rockies. This not only ends the severe weather
threat as it arrives, it also introduces a renewed fire weather
threat. The combination of humidity falling to 25 percent or lower
and WSW winds near 15 mph will lead to near Red Flag conditions for
areas behind this boundary and south of the surface low track. The
Red Flag Warning largely remains for the same areas, although the
northern periphery was removed as these areas will be near or just
north of the surface low track and won`t have access to the extreme
dry air this afternoon. In this well-mixed environment we`ll see
temperatures climbing into the 70s again. While daily record highs
today are a bit warmer than yesterdays, if the more extreme mixing
materializes we could come close once again.

As the low pushes east this evening, the cold air just north of it
begins to wrap in behind it. This will finally shut off our recent
warmth and return us back to the reality of February weather. It
won`t be extremely cold by winter standards, but it will be back to
near or slightly below normal for the date, and some 20 degrees
colder than it has been. Look for highs mostly in the 40s and lows
below freezing in this air mass.

Kimble

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 257 AM CST Thu Feb 19 2026

This weekend we see the last gasps of the western US trough finally
exiting eastward through the Southern Plains and into the
Mississippi Valley. Guidance has largely consolidated around the
idea of a further south penetration of the surface front, cutting
off much of the available moisture when this trough moves through on
Saturday. So while Saturday remains our next best chance for
precipitation (snow), those chances have decreased relative to prior
forecasts. Among the 00Z ensemble guidance, only 20 to 30 percent of
members produce precipitation (mostly snow) in the 24 hours ending
Saturday night. This wave`s passage will introduce a reinforcing
shot of cold air with it, though. So temperatures actually get even
a bit colder Sunday into Monday with highs mainly in the 30s.
Dewpoints dropping into the low teens set a low floor for
temperatures if we`re able to see a clear, calm night.

Surface high pressure shifts east on Tuesday allowing us access to
warmer air beneath an expanding ridge aloft. Thus we`ll see another
warm up heading into the middle of next week. Although there`s still
considerable uncertainty on just how warm it gets in this warm up,
NBM probability of 60 degrees rises to 50 percent or more by
Wednesday with probability of 70 reaching 20 to 30 percent Wednesday
into Thursday.

Kimble

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1125 AM CST Thu Feb 19 2026

Showers and thunderstorms are moving eastward through the CWA this
afternoon, producing small hail and reduced visibilities as low as
2SM as they pass. Thunderstorms are forecast to strengthen as they
enter south-central IL, and may become capable of producing
tornadoes and damaging winds as well as severe hail. After the
storms exit, gusty winds will become impactful with gusts up to 30
kts expected at times. Low MVFR ceilings will also make a return
in locations north of I-70 for a few hours tonight before exiting
in the morning.

Jaja

&&

.CLIMATE...
Issued at 257 AM CST Thu Feb 19 2026

Today is the last day of the very warm weather. Although record
highs are higher than yesterday, there remains an outside chance
that these records may be challenged if all variables line up.
Here are record highs at our three official climate stations:

        Thursday 2/19
KSTL       77/2016
KCOU       77/2017
KUIN       72/2017


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Red Flag Warning until 8 PM CST this evening for Audrain MO-
     Boone MO-Callaway MO-Cole MO-Crawford MO-Dent MO-Franklin
     MO-Gasconade MO-Iron MO-Moniteau MO-Monroe MO-Osage MO-
     Reynolds MO-Washington MO.

IL...None.
&&

$$

WFO LSX