Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

726
FXUS63 KLSX 141736
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1236 PM CDT Thu May 14 2026

.KEY MESSAGES...

- Warm and humid conditions are expected Friday through the
  weekend. Although occasional rounds of thunderstorms are
  expected, the severe weather threat is low.

- A cold front early next week will bring a more focused regional
  threat for severe thunderstorms Monday or Tuesday.


&&

.SHORT TERM...  (Through Late Friday Afternoon)
Issued at 307 AM CDT Thu May 14 2026

Surface high pressure moves east today opening us up to a southerly
return flow. For today, those winds just bring recycled cool, dry
air, but with another day of May sunshine temperatures will rise 1
to 3 degrees over yesterday`s highs despite the chilly start.
Moisture return doesn`t begin until tonight when a low level jet
begins to advect moisture in from the southwest. Guidance is in
pretty good agreement that this will trigger some showers and
thunderstorms mainly across northern Missouri around midnight, with
these moving east or southeast through the early morning hours.
Given this setup, these storms will be elevated in nature with their
strength dependent on how much instability (moisture) can get here.
In a worst case scenario, stronger updrafts could produce marginally
severe hail or a localized downburst, but the overall severe weather
threat is low.

Kimble

&&

.LONG TERM...  (Friday Night through Wednesday)
Issued at 307 AM CDT Thu May 14 2026

Friday through Sunday we will find ourselves in a warm, humid air
mass beneath a flat topped ridge. Dewpoints rise through the 60s and
daytime temperatures warm into the 80s. This warm and humid combo
will provide for plenty of instability daily, though the available
wind shear remains weak. Thunderstorms will likely be focused around
subtle shortwave troughs tracking through the nearly zonal flow atop
the ridge. While guidance is starting to better hone in on the
favored timing and location for these rounds of storms, there`s
still a lot of uncertainty around that. While I wouldn`t be
surprised to see our area highlighted in a Marginal (level 1) severe
risk nearly every day during this period due to the instability
available, the weak shear will limit the potential for organized
severe storms. Locally severe hail or brief downbursts would be the
primary threats.

As we head into early next week, the pattern begins to shift. A
trough digging in the Intermountain West sets up a southwesterly mid
level flow from the Southern Plains to the Great Lakes. With the
warm and humid air mass in place at the surface and increasing shear
aloft, the severe weather potential will increase. The greatest
uncertainty revolves around that trough. Will the trough push
eastward fairly quickly or will it linger and instead send out
smaller pieces of energy each day for a few days?

In the quicker scenario (generally represented by the operational
GFS), a stronger trough pushes east on Monday along with a surface
cold front. This would produce a round of severe thunderstorms in
the vicinity of the front, with the front moving through our region
Monday night. In this scenario, the primary threat area would be
focused over the Plains just to our west, with the front moving
through our area as diurnal instability is waning.

In the slower, piecemeal scenario (represented partially by the
operational ECMWF), multiple weaker waves eject from the broader
trough which gives the front a much slower progression eastward.
This would lead to a multi-day severe weather threat, with the
threat locally focused on when the front finally moves through our
area Tuesday or even Wednesday. This scenario would also tend to
have less available wind shear, so the overall severe threat may be
a bit less.

While there`s still a lot of uncertainty on how this evolves, it`s
clear that early next week represents our next best threat for
severe thunderstorms. The overall threat does not look as high as
what we saw a couple of weeks ago with the April 27 outbreak. Our
shear won`t be as strong and the forcing likely won`t be as focused
on our area during peak heating. That said, depending on how things
evolve there could develop a locally greater threat with large hail,
damaging winds, and tornadoes all possible. A local flash flood
threat may also develop if storms linger in this very humid air
mass.

Kimble

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1235 PM CDT Thu May 14 2026

Dry and VFR flight conditions will continue until overnight tonight
when showers and thunderstorms are expected to develop across
northern MO and progress east/southeastward toward/along and east of
the Mississippi River early Friday morning, possibly growing into a
cluster/complex. Confidence is highest in impacts at KUIN but is
also high enough at KCOU and St. Louis metro terminals for PROB30
groups. In the strong/most intense thunderstorms, IFR flight
conditions and small hail are likely. Otherwise, southeasterly
winds will eventually become southerly on Friday as a warm front
lift northward.

Pfahler

&&

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

$$

WFO LSX