Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

763
FXUS63 KLSX 172339
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
539 PM CST Tue Feb 17 2026

.KEY MESSAGES...

-Elevated fire weather conditions are expected north of I-70 on
Wednesday and across central and southeast Missouri on Thursday
afternoon.

-A few severe thunderstorms are possible Thursday afternoon and
evening, largely along and east of the Mississippi River. Tornadoes
and damaging winds are the main threats.

-A cold front will move through Thursday evening, bringing cooler
temperatures back to the region.


&&

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 134 PM CST Tue Feb 17 2026

A surface low currently positioned near the Dakotas is progressing
eastward today, and southerly flow ahead of the system combined with
a warm start to help temperatures largely into the 50s by 1 PM.
Clouds have effectively stunted temperatures, particularly across
southeast Missouri and south-central Illinois where low clouds have
persisted through the day. This low will continue to progress
eastward, driven by a mid-level shortwave caught within the flow of
a broad trough over the western half of the CONUS. An associated
dryline/Pacific front will slide through the forecast area
overnight, passing through largely dry. While some hi-res cams spit
out a few showers, confidence is low that convergence along the
front will be enough to generate any rain. Any rain that does occur
will be very light, a hundredth or two at most.

Gusty winds will continue overnight, keeping temperatures elevated.
Lows are forecast in the upper 40s to mid 50s, which is above normal
for high temperatures this time of year, let alone low temperatures.
The very warm start Wednesday combined with deeper mixing to access
850mb temperatures in the upper single digits and warming from
downsloping off the Ozarks will push high temperatures near record
values area wide (see Climate Section). These warm temperatures and
the dry airmass behind the dryline/Pacific front will generate low
RH values through the day. HREF probabilities indicate a 70-100%
chance for RH values to drop below 30% across most of the forecast
area, with the greatest probabilities across central and northeast
Missouri and west-central Illinois. This is also where winds are
expected to remain elevated, above 12 mph through the afternoon,
resulting in Elevated Fire Danger from roughly 10 AM to 6 PM. For
more information please see our Fire Weather Planning Forecast.
Delia

&&

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 134 PM CST Tue Feb 17 2026

Elevated fire conditions are expected again on Thursday afternoon
across central and southeast Missouri where southwesterly flow will
once again produce locally warmer and drier conditions, combined
with increased winds from the approaching system.

Focus now turns to the threat for severe weather Thursday afternoon
and evening ahead of and along a cold front that will push through
the region associated with another surface low and mid-level wave
spinning through the mid-level trough. Confidence is growing that
instability will develop along and east of the Mississippi River
Thursday ahead of the approaching front. NBM guidance (which is
starting to include some of the short term guidance) indicates 150-
450 J/kg of surface based CAPE within the interquartile spread. With
60-90 kts of 0-6 km shear, this range indicates a lower potential
(low end instability) to more confident potential (high end
instability) for severe thunderstorms. The best instability is
across central Illinois, with lower confidence in high surface based
CAPE values as we get closer to the Mississippi River. This is
reflected in the SPC Day 3 outlook. The shear is largely parallel to
the front, and low-topped supercells are favored from this pattern.
In addition to uncertainty in how much instability will generate
across the eastern forecast area, soundings have been highlighting
a low-level warm nose around 850mb that could stunt convective
growth unless we`re able to mix it out. Recent guidance has trended
the surface low 100 miles or so northward, allowing for surface
winds to become more backed and introducing more curvature in the
low-level hodographs. This increases confidence that a few tornadoes
could result in addition to damaging winds from any severe
thunderstorms that develop.

The surface cold front will push through the area overnight Thursday
into Friday, ushering in cold air that will bring temperatures
closer to normal for the weekend. At the same time the mid-level
trough responsible for all these waves and associated fronts will
kick east and weaken, bringing one final wave through the central
CONUS this weekend. There are differences in timing of this feature
and that translates to differences in the timing of the
precipitation Saturday into Sunday, and also what kind of
precipitation falls. If precipitation falls overnight, it`s more
likely to fall as snow, but day time temperatures have a 50-80%
chance of exceeding 34 degrees, increasing confidence that daytime
precipitation would fall as rain or a rain/snow mix. More is still
to come in terms of details with this system, but probabilities of
exceeding 0.1" of liquid QPF peak in southeast Missouri and southern
Illinois at 30%. This increases confidence that even if wintry
precipitation does fall, amounts are not currently expected to be
impactful.

The mid-level trough will exit the forecast area over the weekend,
allowing a mid-level ridge to begin building back into the central
CONUS. Temperatures are expected to warm in response, a trend that
is apparent in the NBM high temperature interquartile spread despite
the 10 degree interquartile spread.

Delia

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 511 PM CST Tue Feb 17 2026

MVFR and IFR clouds largely east of the Mississippi River have
been slow to exit to the east, with some backbuilding even
affecting KSTL and KCPS. These fringe terminals should expect
intermittent MVFR ceilings through this evening. Gusty southerly
winds will continue into tonight. The potential for LLWS is
contingent on how elevated these winds remain tonight. Maintained
them in the TAFs, but this may need to be amended out later.
Otherwise, tonight`s gusty southerly winds will shift to westerly
and diminish tomorrow, and VFR conditions will prevail as soon as
the aforementioned MVFR/IFR cloud deck exits.

Jaja

&&

.CLIMATE...
Issued at 232 AM CST Sat Feb 14 2026

Daily record high temperatures may be threatened this week. Here
are records between Tuesday 2/17 and Thursday 2/19 at our three
official climate stations:

        Wednesday 2/18      Thursday 2/19
KSTL       74/1971             77/2016
KCOU       71/2017             77/2017
KUIN       68/2017             72/2017


&&

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

$$

WFO LSX