941
FXUS63 KLSX 050400
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1100 PM CDT Wed Jun 4 2025

.KEY MESSAGES...

- There is a chance of strong to marginally severe thunderstorms this
  afternoon. Damaging winds will be the primary threat.

- Our active pattern continues through this weekend with our next
  chance of thunderstorms occurring on Friday.


&&

.SHORT TERM...  (Through Late Thursday Night)
Issued at 141 PM CDT Wed Jun 4 2025

The cold front responsible for forcing last night`s thunderstorms
currently splits Missouri and Illinois and extends from about Joplin
to Chicago. Moisture remains plentiful in the vicinity of the front
with dewpoints in the 60s and PWATs of around 1.8". Forcing from the
system`s parent mid-level trough and the low-level jet have kept
precipitation going, but coverage of showers and thunderstorms have
decreased through the early afternoon as influence from these
features has waned through the day. Although coverage has been
lesser than this morning, strength of thunderstorms is increasing as
SBCAPE reaches near 1000 J/kg ahead of the front and despite the
abundant cloud cover. Even so, only some thunderstorms are expected
to become strong to severe. Model soundings show very shallow, very
short-lived mixed boundary layers underneath tall, skinny CAPE
profiles and modest shear. This is not a good set-up for severe
hail. Thunderstorms that do become strong would be capable of
marginally severe winds and perhaps a brief tornado owing to
backed surface winds and thus curved hodographs. Updraft
interaction will have a negative impact on tornado development,
but it can`t be ruled out.

The front will push southeast of the area tonight and will carry the
greatest chance for showers and thunderstorms in that direction.
Portions of southeast Missouri and southern Illinois will still have
a 60 - 80% chance of precipitation as they`ll be closer to the
boundary. Otherwise, Thursday will be drier and a few degrees
warmer (mid-70s to low-80s) for most locations than what we`ve
seen today.

Jaja

&&

.LONG TERM...  (Friday through Next Wednesday)
Issued at 141 PM CDT Wed Jun 4 2025

The chance for showers and thunderstorms ramps up Friday morning as
an MCS passes to our southwest. CAMs show additional thunderstorm
development to the northeast of the feature, which would enter our
CWA around sunrise. With the instability gradient lying well to the
south of this development and the MCS scouring out the rest, these
thunderstorms would likely have a hard time becoming severe unless
they develop or rush out ahead of the MCS within the better
environment. In any case, southeast Missouri has the highest chance
at seeing severe weather on Friday with damaging winds as the
primary threat.

The active pattern is expected to continue through early next week
as the front remains stationed just south of us. Rain and
thunderstorm chances, though still existent, will decrease Sunday
and Monday since the most favorable environment will be to our
south. A cold front is forecast to shove the stationary boundary out
of the Ohio Valley early next week and usher in a period of drier
weather. Temperatures until then will gradually moderate with highs
on Friday in the 70s to 80 degrees warming to widespread low-80s by
Sunday. The cold front is not expected to be potent due to weak,
short-lived cold air advection behind the front. Thus, low 80s are
still forecast for early next week.

Jaja

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1100 PM CDT Wed Jun 4 2025

IFR ceilings are expected to cover much of the region overnight,
accompanied by additional scattered showers and patchy drizzle and
fog that could lower visibilities at times. KUIN will likely remain
at the northern edge of lower ceilings with flight conditions
varying between MVFR and VFR. Gradual improvement in flight
conditions is expected Thursday morning through the afternoon via
scattering/lifting of lower ceilings. The quickest improvement will
be at KUIN, followed by KCOU and KJEF with VFR flight conditions
forecast by late afternoon. At St. Louis metro terminals, VFR flight
conditions may not be achieved before the end of the TAF period.

Pfahler

&&

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

$$

WFO LSX