207
FXUS63 KLSX 022330
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
630 PM CDT Mon Jun 2 2025

.KEY MESSAGES...

- Thunderstorm chances return to the region on Tuesday. While the
  severe weather threat is limited, thunderstorms may produce
  locally heavy rainfall in central to northeast Missouri.

- A stalling front keeps rain chances in the forecast through at
  least Friday.


&&

.SHORT TERM...  (Through Late Tuesday Night)
Issued at 234 PM CDT Mon Jun 2 2025

Our stretch of dry weather and high altitude smoke is coming to an
end. The mid level ridge axis is currently shifting overhead in
response to a trough moving east across the Rocky Mountains. The
shift in wind direction aloft will finally push the smoky skies off
to the east, while the approach of the trough will initiate our next
period of wet weather.

Moist advection has already begun over the Southern Plains in
advance of the approaching trough. Mid to upper 60s dewpoints have
spread well into Kansas with 70+ dewpoints into central Oklahoma.
Convective initiation is expected this evening within this moisture
plume with moisture being advected northeastward on a low level jet
toward our area as early as Tuesday morning. Thunderstorms will be
decreasing in intensity and organization as they head toward our
area, but their presence across central Missouri Tuesday morning
will herald the arrival of the better moisture. Where clouds are
more extensive on Tuesday (mainly central to northeast MO),
temperatures will be a bit more limited. But where we see more sun
we`ll see temperatures rise into the upper 80s to near 90, the
hottest day of this air mass.

While there may be a break in the showers and storms around midday
into the afternoon, a cold front approaching from the northwest will
provide a greater focus for convective development Tuesday evening
and into the overnight. Instability and shear Tuesday evening will
be just enough to produce at least a minor severe weather threat.
Steering flow parallel to the initiating boundary suggests lots of
storm interaction with convective clusters or a broader line of
storms being the primary storm mode. Shear is strongest in the low
levels, so if any storms can remain a bit more isolated they may
pose a brief tornado and hail threat, but the primary severe weather
threat will be damaging winds during the evening hours.

Moisture will be maximizing near the front Tuesday night with HREF
mean precipitable water values around 1.8 inches. This suggests that
storms will be capable of producing heavy rainfall rates of 1 to 2
inches per hour. With the front slowing with time we may see some of
these heavier rain producing storms linger over the same areas for 2
to 3 hours producing a greater threat for flash flooding. This is
most likely across central to northeast Missouri where a Flash Flood
Watch has been issued. Convection decreases in intensity and
coverage by Wednesday morning as convergence on the low level front
decreases.

Kimble

&&

.LONG TERM...  (Wednesday through Next Monday)
Issued at 234 PM CDT Mon Jun 2 2025

Tuesday night`s front stalls in the central to southern parts of our
area Wednesday and lingers into Thursday. This front will serve as a
focus for additional thunderstorms, though convergence along the
front will be decreasing leading to more scattered and perhaps
diurnally driven activity. Wind shear will be lower as well, keeping
the severe weather threat low. While the area of convection remains
relatively stationary with the remnant front, precipitable water
values decrease a bit and convection is expected to be more
scattered rather than persistent, limiting the flash flood threat
Wednesday and Thursday.

The next more organized shortwave trough moves through the region on
Friday and is likely to produce a more widespread area of showers
and storms as it moves through. Depending on how this organizes we
could see an uptick in the severe weather or flash flooding threat,
but guidance is still honing in on this wave so our confidence in
these threats remains low.

Flow remains somewhat zonal behind Friday`s trough, with additional
waves potentially bringing new opportunities for showers and storms
through the weekend. However, with Friday`s trough being a bit
stronger it could shove the frontal boundary southward behind it,
shifting the weekend rain chances south as well. So while we do
still have at least some minor PoPs this weekend due to the
uncertainty with the next several waves moving through the zonal
flow, we do stand a better chance of seeing some drier weather this
weekend.

Temperatures the rest of this week and this weekend will vary based
on where the front lands and how much cloud cover lingers, but with
the ridge having flattened out our high end potential will be lower.
On the warm side of things we`ll reach the mid 80s, but with more
clouds we may not rise out of the 70s.

Kimble

&&

.AVIATION...  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 626 PM CDT Mon Jun 2 2025

Scattered showers and a few thunderstorms are expected to approach
parts of central Missouri early Tuesday morning. This activity
should weaken and dissipate with time and eastward extent. Brief
reductions in visibility are expected with any thunderstorms that
directly impact any terminal. Chances for showers and
thunderstorms hit a lull in the afternoon before increasing again
along/ahead of a cold front Tuesday evening.

Gosselin

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch from Tuesday evening through Wednesday morning for
     Audrain MO-Boone MO-Callaway MO-Cole MO-Knox MO-Lewis MO-
     Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike
     MO-Ralls MO-Shelby MO.

IL...None.
&&

$$

WFO LSX