Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

281
FXUS63 KLSX 161919
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
219 PM CDT Thu Apr 16 2026

.KEY MESSAGES...

- The threat of isolated to scattered showers and thunderstorms
  will continue across southeastern Missouri through early this
  evening. A storm or two will be capable of primarily large hail.

- Widespread thunderstorms are expected Friday afternoon and evening
  along a cold front. Several thunderstorms will be capable of
  damaging wind gusts, with large hail and tornadoes being
  secondary threats.


&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 217 PM CDT Thu Apr 16 2026

Thunderstorms have formed across southeastern Missouri this
afternoon roughly at the nose of a wing of warm air advection.
Subtle forcing from this advection paired with lift from the axis of
a weak shortwave aloft will lead to a low threat (20-40% chance) for
showers and thunderstorms centered on southeastern Missouri through
early this evening. Instability in this part of the area continues
to build, with SPC mesoanalysis showing 2,000-2,500 J/kg of MLCAPE
present along and south of I-70. Continuing warm air advection
through this evening will sustain this instability and advect it
slightly east-northeastward through this evening. Deep-layer shear
is progged to remain around 30 kts, favoring multicells with brief
supercellular structures. This environment favors large hail as the
primary threat, with DCAPE right around 1,000 J/kg leading to
damaging wind gusts being a secondary threat. Weak low-level shear
and meager SRH are expected to mitigate a threat of tornadoes.
Weakening lapse rates and a strengthening cap later this evening (8-
9pm) will end the threat of convection.


Tomorrow, an upper-level trough will eject out into the Great
Plains, enhancing southwesterly flow over the Middle Mississippi
Valley. At the surface, a low will deepen over the Central Plains
and move into the Upper Midwest, sweeping a cold front across the
Plains and Midwest. Ahead of this front during the afternoon over
the Middle Mississippi Valley, guidance continues to point to a very
unstable airmass characterized by 3,000-4,000 J/kg of SBCAPE. The
approaching trough and a low-level jet ramping up over the region
will increase deep-layer shear through the day, with generally 30-40
kts forecast among hi-res guidance.

While model soundings show capping through much of the afternoon,
the approaching front paired with lift via a leading shortwave and
jet streak coupling will spawn updrafts across western and northern
Missouri during the mid to late afternoon along and ahead of the
front. Given the amount of shear and instability, a multicellular
and supercellular storm modes are anticipated. The degree of forcing
will lead to numerous updrafts forming in close proximity, favoring
storm interaction and upscale growth into a convective line quickly.
While storms are discrete, the large hail threat will be greatest,
with the strongest updrafts capable of hail up to around 2.5" in
diameter. Relative to our CWA, this threat is greatest across far
northeastern Missouri where a minority of guidance produces discrete
convection prior to upscale growth.

Confidence is high that storms will grow upscale into a squall line
prior to entering the rest of the CWA. Steep low-level lapse rates
favor a damaging wind threat with both discrete storms and bowing
segments within the squall line. With guidance consensus favoring 20-
25 kts of 0-1 km shear and a little over 150 m2/s2 of SRH within the
same layer, there is a low tornado threat with either storm mode.
Bulk 0-3 km shear of 30-35 kts will favor mesovortex development
within the squall line, though guidance differs on the orientation
of the vector. A more west-east orientation would favor a greater
QLCS tornado threat, while a southwest-northeast orientation limits
the threat to the northern periphery of bowing segments.

The threats are expected to peak late afternoon into the early
evening across central and northeastern Missouri. As the line moves
further eastward, diminishing instability will lead to a weakening
trend during the late evening and overnight hours. The aforementioned
robust forcing will continue overnight, leading to an expansive area
of stratiform rainfall that will continue through early Saturday
morning.

Elmore

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 217 PM CDT Thu Apr 16 2026

Early Saturday, the aforementioned trough will continue to edge
eastward through the Midwest per guidance consensus, pushing
Friday`s front deeper into the Ohio Valley. With upper-level flow
not becoming northwesterly until Sunday and the core of the post-
frontal airmass remaining north of the CWA, we will miss out on the
coldest temperatures. However, the majority of ensemble guidance
favors values below climatology through the weekend, with a low
chance for frost for portions of the area Saturday night and Sunday
morning.

Ridging quickly builds into the region Monday per both ensemble
clusters and deterministic models, with southwesterly low-level flow
returning to the Middle Mississippi Valley. Guidance supports this
pattern continuing through midweek, corresponding with temperatures
gradually warming to and then above normal by Wednesday-Thursday.

Elmore

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1239 PM CDT Thu Apr 16 2026

Dry and VFR flight conditions are expected through a majority of
the period at all local terminals. Showers and thunderstorms this
afternoon and evening are expected to remain south of the local
terminals. Another round of showers and thunderstorms is expected
tomorrow evening along a cold front, just beyond the end of the
current period.

Elmore

&&

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

$$

WFO LSX