Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

129
FXUS63 KLSX 141904
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
204 PM CDT Wed Oct 14 2026

.KEY MESSAGES...

- Widespread showers and thunderstorms are expected late
  tonight into Thursday morning.

- Additional, potential shower and thunderstorm development
  during the afternoon and evening could include a severe
  thunderstorm or two with isolated damaging winds and,
  conditionally, a brief tornado.

- Behind a cold front Thursday night, temperatures will become
  much cooler and seasonable, with a warming trend early next
  week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 203 PM CDT Wed Oct 14 2026

Waves of widespread showers and thunderstorms have shifted much
further southward into southern MO and AR this afternoon--most of
which will remain to the south/southwest of the CWA through this
evening aside from a few light showers or sprinkles. The effective
front has also been pushed south of the CWA by this activity,
leading to a much cooler day beneath considerable cloud cover, but
high temperatures in the upper 60s and 70s F are still above average
for mid-October. Not only that, but dewpoints are still running
above the 90th climatological percentile, leading to an atypical
mugginess.

In response to the northeastward ejection of an upper-level trough
currently over the Four Corners Region, the aforementioned front
will advance northward tonight into Thursday as surface cyclogenesis
ensues near the NM-TX border. A wing of associated low to mid-level
isentropic ascent/WAA will drive a broad area of showers and
thunderstorms that lifts northeastward through the CWA late tonight
into Thursday morning. With thunderstorms anticipated to be quite
progressive, flash flooding is unlikely but brief high rainfall
rates are anticipated from near-record breaking PW around 2".

The majority of morning showers and thunderstorms will continue to
lift northward and end from south to north Thursday morning ahead of
a surface cyclone tracking northeastward across MO through the day.
There is variability in model guidance on how deep/mature the
cyclone gets and how far the warm front lifts and warm sector
expands across the CWA. These details along with the amount of
lingering cloud cover will have ramifications on temperatures,
instability, and more importantly how thunderstorms redevelop during
the afternoon. With 40 to 50 kt of deep-layer wind shear, there is a
concern for severe thunderstorms if enough instability becomes
available. Upward trends in successive runs of the HREF and REFS
SBCAPE is slowly increasing confidence in sufficient instability
with the interquartile range now around 1000 to nearly 2000 J/kg in
the warm sector. Timing, coverage, and location of thunderstorms is
not clear, but the most favored location would be near east-central
MO into IL where convergence is greater near the surface cyclone.
Surface winds are projected to be veering in the warm sector, but
backed winds near the warm front just ahead of the cyclone could
increase low-level hodograph curvature enough for a brief tornado.
Otherwise, isolated damaging winds are the greatest threat in a
mixed mode of QLCS segments and supercells, with potential
additional development along the trailing cold front southward
through the evening.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 203 PM CDT Wed Oct 14 2026

The cold front will progress eastward Thursday evening into
overnight, but some showers could linger behind the front well into
into the night along/east of I-44/I-55. The primary impact of the
front will be the onset of strong low-level CAA that persists
through the day Friday. In fact, Friday`s calendar day high
temperature will be at midnight with temperatures falling and then
wavering in the 40s and 50s F through the day Friday beneath
insolation limited by extensive stratocumulus and even isolated
showers in the cyclonic flow region beneath the main upper-level
trough. Occasional northwesterly winds gusting 25 to 35 mph will
further exacerbate the chill of these much cooler temperatures.

The seasonable cool airmass will support high temperatures in the
50s and low-60s F on Saturday and low temperatures in the mid-30s to
low-40s F Saturday morning and Sunday morning. Uncertainties in
lingering cloud cover Friday night and the positioning of a surface
anticyclone decrease confidence in how widespread frost will be
those mornings, dependent on how optimal radiational cooling and BL
decoupling are. It is worth noting that global ensemble model and
NBM-based probabilities of low temperatures below 36 F, a reasonable
proxy for initial frost formation, have been slowly increasing for
low-lying and rural areas.

Global model guidance is in good agreement that a warming trend back
to above average will take place Sunday through early next week as
the anticyclone migrates to the east and weak but persistent low-
level WAA begins. In the southwesterly upper-level flow pattern,
model guidance is having a more difficult time resolving a potential
passing upper-level trough that only a small amount (<15 percent) of
ensemble membership has producing light showers in minimal moisture
return. Therefore, dry conditions are more than likely to prevail
through the weekend and early next week.

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1240 PM CDT Wed Oct 14 2026

Mainly dry conditions aside from a few sprinkles are expected
through this evening with some gradual decrease in MVFR ceilings.
These ceilings will be most persistent at KCOU and KUIN. An area of
showers and thunderstorms will lift northward through the area late
tonight into Thursday morning, accompanied by MVFR to IFR flight
conditions in the heaviest rainfall. Flight conditions will improve
from north to south on Thursday as a warm front lifts northward,
likely to VFR during the afternoon at St. Louis metro terminals.
Showers and thunderstorms are forecast to redevelop during the
afternoon and evening as well, but with uncertainties in the details
and them being near or beyond the end of the TAF period preclude
inclusion. Outside of thunderstorms, winds will be light.

&&

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

&&

$$

SHORT TERM...Pfahler
LONG TERM...Pfahler
AVIATION...Pfahler