Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

134
FXUS63 KLSX 140759
AFDLSX

Area Forecast Discussion
National Weather Service St Louis MO
259 AM CDT Wed Oct 14 2026

.KEY MESSAGES...

- Weakening thunderstorms continue to move through the area this
  morning with activity on the downward trend my late morning.

- Another round of thunderstorms moves into the area late
  tonight into Thursday. There is isolated damaging wind
  potential with the strongest cells.

- A strong cold front brings much cooler and drier conditions
  late week into the first half of next weekend.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 216 AM CDT Wed Oct 14 2026

Thunderstorms will continue to move through the area early this
morning. The airmass was recently worked over by an initial cluster,
which sent outflow well south of I-70 between 06z-07z. A second line
has entered the area and is expected to impact on southern sections
of the CWA before overall activity wanes later this morning into the
afternoon.

The second cluster of thunderstorms continues to move west to east
with ASOS observations at KCOU reporting gusts of 32 knots (0615z)
and KJEF peaking at 26 knots (0623z). Radar trends show the line
becoming increasingly broken and outflow dominant. IR satellite
also indicates warming in the cloud tops along with a decrease in
lightning frequency. A few embedded thunderstorms remain possible
with some gusty winds and locally heavy rainfall, along with a
general southward shift in the better convective potential. The
airmass remains undisturbed over parts of southeast MO and southwest
IL with MUCAPE values of 1100-1300 J/kg and 30-35 knots of shear.
Severe weather is not anticipated, however, as what remains is
likely to be elevated.

Trends continue to show precipitation potential exiting a little
quicker as air become more stable over central/northeast MO and west-
central IL around 12z and the remainder of the area trends in that
direction as outflow shunts instability toward the AR border. An
isolated shower remains possible, though much of the remainder of
the day trends drier. Latest PoPs may still be a little high with
further adjustment needed to lower probabilities, especially along
and north of I-70. HREF ensemble guidance shows a wide range in
total cloud coverage as upper ascent remain over the area. The
question is whether we clear out enough and/or recover enough to
produce addition, diurnally charged instability for afternoon
thunderstorms along the front. As of now, the severe potential looks
limited at best with low CAPE, less shear, and exit of early day
upper ascent that supported the morning activity. Therefore, the day
1 marginal is not being messaged.

Tonight into Thursday brings another round of thunderstorms,
initially from the southwest, as a more potent vort
max/shortwave tracks northeast from eastern KS through northern
MO. This draws the warm sector back toward Hwy 36 (MO)/I-72
(IL) along with higher CAPE advecting northeastward into
southeast and east-central MO and southwest IL. Timing looks to
be key here, too, as the northward advancement of warm air
gives rise to a broad area of showers and thunderstorms. The
warm sector includes 40-50 knots of shear, though individual
short range guidance varies on the magnitude of instability and
mid-level lapse rates are weak. HREF shows the uncertainty with
a wide IQR spread, but even the 75th percentile is around
1000-1200 J/kg. If thunderstorms can intensify enough, isolated
damaging winds are the primary threat. Tornadoes look unlikely
as the warm air advances north of the CWA little to no backing
in the wind. Latest RAP guidance shows almost no turning in the
hodographs with unidirectional flow as the cold front quickly
advances west to east through late evening. Short/medium range
guidance is in good agreement with the cold front advancing from
KUIN/KCOU around 02z to the metro around 05z and east of the
area around 08z or so.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 228 AM CDT Wed Oct 14 2026

Much cooler and drier air will begin spilling into the region
through Thursday night. Seasonably cool, below normal
temperatures extend through the upcoming weekend before
moderating back above normal early next week.

A long wave trough advances east-southeast from the southern
Canadian Provinces and over the Great Lakes Thursday night into
Friday morning. RAP guidance shows strong cold air advections
with a 15-20C drop in mid-level temperatures as the axis over
the trough crosses the region between 06z-12z. Behind the
trough a strong surface high sets the the stage for
northwesterly flow and rapidly cooling temperatures through
Friday morning. Friday morning temperatures may even be somewhat
deceiving for early-risers as southeast sections of the CWA
remain in the 50s/low-60s, only to continue to cool as we
progress through Friday morning. Temperatures aren`t likely to
recover much from there with partial cloud cover and cold air
advection. While both Friday and Saturday temperatures are
fairly similar (mid-50s/low-60s). The primary focus will be on
Saturday and Sunday morning lows as NBM guidance is likely too
cold with mid-30s being too broadly represented. This is due in
part to prior guidance showing the surface high overhead
Saturday morning, which now is further west, centered over the
eastern Plains. The surface high moves east into the Ohio Valley
and mid-Atlantic Region by Sunday morning. Suffice to say, some
of the coolest fall temperatures will still be felt and the
narrowing in the IQR data for each morning lends better
confidence for low-40s being well represented with mid-30s
confined to micro climate behavior that is typically more
isolated. I would not be surprised to see NBM guidance inch
upward with morning low over the next couple of days.

The moderating trend continues into early next week, though
there is enough spread (5-7 degrees) in the long range guidance
to lower confidence in the magnitude of warmth. That said, most
areas do return to the 70s Monday into Tuesday.

&&

.AVIATION /00Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1118 PM CDT Tue Oct 13 2026

Showers and thunderstorms will affect the area for the remainder
of the night. Thunderstorms will be capable of producing wind
gusts to 35-40kts and IFR visibilities in locally heavy rain.
The cold front which triggered these storms will drift southeast
into the area and stall near the I-70 corridor by late Wednesday
morning. Ceilings are expected to fall to below 2000 ft
Wednesday morning across much of the area, and some scattered
IFR ceilings are also possible, but confidence in widespread
IFR remains low. Some improvement in ceiling heights is possible
Wednesday afternoon, though bases will likely remain at or below
3000 ft.

&&

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

&&

$$

SHORT TERM...Maples
LONG TERM...Maples
AVIATION...Carney