975
FXUS63 KLSX 300811 CCA
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
301 AM CDT Thu May 30 2024

.KEY MESSAGES...

- The next best chance of rain will be Friday evening through
  Saturday, with limited thunderstorm potential.

- The region returns to a warm and active pattern for the work
  week.


&&

.SHORT TERM... (Through Late Friday Night)
Issued at 253 AM CDT Thu May 30 2024

Mid-level water vapor imagery shows a trough over the Great Lakes
region, extending into the Ohio River Valley, and a ridge across the
central CONUS. A shortwave is evident in the western side of the
ridge, and a weak surface low has formed across western Kansas this
morning. The current northwesterly mid-level flow will turn
southwesterly today with the approach of the ridge axis and the
shortwave. The southwesterly flow will push a warm front northeast
through the forecast area today, bringing warm, moist air into
the region ahead of the surface low and associated precipitation.
Today will be a few degrees warmer than yesterday, while the
approach of the ridge axis will keep the area dry.

The surface low will approach the region overnight tonight into
tomorrow morning, and warm air advection precipitation is possible
as early as late morning Friday across central Missouri. The best
chance for rain will be near the surface low as it pushes through
Friday evening into Saturday, as this is where the best ascent
will be. Thunderstorms will be largely isolated as instability
will be greatly limited (generally less than 200 J/kg of MUCAPE),
but I can`t rule out a few rumbles of thunder. Given the lack of
widespread instability, I expect rain to be more uniform in
distribution rather than showery. QPF amounts will be beneficial but
not concerning, given the lack of instability. By Sunday evening the
probability of 0.5 inches of total precipitation is 50-80%, while
the probabilities of 1 inch of rain or more peak near 40% across
central Missouri.

MRM

&&

.LONG TERM... (Saturday through Wednesday)
Issued at 253 AM CDT Thu May 30 2024

The surface low and associated precipitation will continue its
march northeastward in step with the movement of the mid-level
shortwave. Mid- and low-level subsidence in the wake of the
shortwave will help to clear precipitation from the region
Saturday, but showers could still linger into the afternoon hours.
A weak surface high will build into the region overnight, but it
will quickly move east and put the region back into southerly
surface flow. Southerly flow and daytime heating may be enough to
generate some instability across the region during the day Sunday,
deterministic global guidance shows anywhere from 100-1400 J/kg
(that`s not a typo) of MUCAPE Sunday afternoon. Areas that see
instability on the higher end of that wide spectrum could see a
few pop-up showers and thunderstorms during the afternoon hours.
Despite this chance for isolated precipitation, most areas will be
dry through the day Sunday.

In the wake of the weekend shortwave the mid-level pattern will
become quasi-zonal, leaving the region open to multiple shortwaves
to move through the mid-Mississippi Valley. There are differences in
the timing, location, and intensity of these shortwaves across the
ensembles, which accounts for the isolated to numerous mention of
showers and thunderstorms in the forecast through the work week.
While there is uncertainty in the timing of precipitation,
confidence is high that under this flow regime temperatures will
warm to near or above normal and instability will return to the
region. This reintroduces the potential for strong to severe
thunderstorms across the region, which is highlighted in the CIPS
and CSU guidance, which begin to highlight the mid-Mississippi
Valley for severe thunderstorm potential on days 6 and 7.

MRM

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1043 PM CDT Wed May 29 2024

VFR flight conditions expected through the forecast period.
Otherwise, light and variable winds will become southeasterly by
mid morning on Thursday with scattered diurnal cu developing.

Byrd

&&

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

$$

WFO LSX