019
FXUS63 KLSX 081741
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1241 PM CDT Tue Jul 8 2025

.KEY MESSAGES...

- There is a chance (30-60%) of showers and thunderstorms today.
  Isolated severe thunderstorms are possible capable of producing
  damaging wind gusts to 60 mph and a localized threat for heavy
  rainfall.

- There will be additional chances for showers and thunderstorms through
  the weekend with the best chance (40-60%) on Friday night and
  Saturday.


&&

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 336 AM CDT Tue Jul 8 2025

An MCS currently over northwest Missouri is expected to continue to
move east and southeast and weaken early this morning as they move
into an environment that is increasingly stable over eastern MO.
This is reflected in the latest CAMS runs which show this line
diminishing before thunderstorms regenerate over the CWA this
afternoon.  This will occur as an upper trough currently over the
middle Missouri Valley will drops southeast into the Missouri and
Illinois later today.  The outflow and potentially an MCV from the
remnant MCS may also aid in the redevelopment of thunderstorms this
afternoon.  While MLCAPES will be in the 1500-2500 J/kg range, deep
layer shear will only be in the 20-30 knot range with most of the
shear in the lower part of the hodograph.  Forecast soundings do
support the potential for isolated damaging winds to 60 mph per the
SPC marginal risk.  In addition, PWATS will be in 1.75 to 2.0"
range, so any slow moving thunderstorms could produce locally heavy
rainfall. It still appears the most likely time for any severe
weather or heavy rainfall will be between 2 and 8 pm.

The rain chances will diminish tonight with the loss of daytime
heating.  The southern end of the upper trough will linger over the
Middle Mississippi Valley on Wednesday bringing additional chances
(20-40%) of showers and thunderstorms over the southeast half of the
CWA on Wednesday afternoon.  High temperatures the next two days
will be seasonably warm in the 85 to 90 degree range as 850 mb
temperatures are in the 15-20C range.

Britt

&&

.LONG TERM...  (Wednesday Night through Monday)
Issued at 336 AM CDT Tue Jul 8 2025

The LREF is showing that the upper pattern from mid week into early
next week will be highlighted by a large high over the southwest
CONUS with Missouri and Illinois on the southern edge of the active
westerlies.   While there will be on and off chance of showers and
thunderstorms over the Midwest as troughs move through the
aforementioned westerlies, the best chance (40-60%) over our area
will be Friday night into Saturday when there is good agreement in
the global models that a upper trough and attendant cold front will
move across Missouri and Illinois.  While the weekend does not look
like a washout, I can`t rule out heavy downpours with some of the
thunderstorms given PWATS around 2".

Temperatures through the period will be close to July normals
ranging from the mid 80s to around 90 degrees.  The NBM is showing
the warmest day on Friday when most areas will see highs in the low
90s and heat indexes near 100 degrees ahead of the front.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1232 PM CDT Tue Jul 8 2025

The primary focus will be the potential for showers and
thunderstorms this afternoon into this evening, a few of which
could be strong to marginally severe. The primary threats will be
locally heavy rain and gust winds, including isolated gusts
approaching 60 mph in the strongest thunderstorms. A few showers
have already developed around KUIN with potential trending
southward as more robust convection initialized across central and
east-central Missouri into southwestern Illinois. Considering the
slight difference in hi-resoultion guidance and scattered nature
of convection, TEMPO groups were utilized to convey the period of
greatest impact. This may be adjusted in later amendments should
initialization of activity be departed from current thoughts. The
strongest cells are likely to result in MVFR ceilings/visibility
for brief periods.

Outside of the thunderstorm potential, VFR conditions are
expected. A few showers and thunderstorms may linger into this
evening, but generally speaking, thunderstorms will move south of
the terminals and weaken after sunset. Light/variable surface
winds will persist into Wednesday.

Maples

&&

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

$$

WFO LSX