561
FXUS63 KLSX 030955
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
455 AM CDT Wed Jun 3 2026

.KEY MESSAGES...

 - Dry weather continues today and Thursday with temperatures
   warming from the low 80s today to the mid 80s on Thursday.

- Temperatures continue to warm into the mid and upper 80s this
  weekend, and more early summer-like humidity returns along with
  the chance for showers and thunderstorms.


&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 324 AM CDT Wed Jun 3 2026

A surface high centered over the Great Lakes region combined
with ridging aloft will continue to produce calm and dry weather for
the Mid Mississippi Valley today. The light wind and mostly clear
sky this morning will allow temperatures to sink into the mid and
upper 50s in most locations by sunrise, and even the lower 50s in
some of our cooler spots. Despite this morning`s lows being 3-5
degrees below normal, strong early June sunshine will raise
temperatures 25+ degrees this afternoon into the low 80s.

The blocky high amplitude pattern with an upper ridge over the
central U.S. and troughs to the east and west will slowly attenuate
and shift east tonight through Thursday.  This will move the surface
high from the Great Lakes to the Atlantic Coast by late Thursday
afternoon.  Surface winds become more southerly across the Mid
Mississippi Valley tonight as this eastward shift happens which will
keep temperatures a few degrees warmer in the mid 50s to around 60.
Highs Thursday afternoon will be correspondingly warmer in the mid
80s.

Carney

&&

.LONG TERM...  (Thursday Night through Tuesday)
Issued at 324 AM CDT Wed Jun 3 2026

The pattern shift causes the western trough to fracture and the
resulting northern stream short wave drifts into the Plains Thursday
into Thursday night.  This short wave gets attenuated somewhat as it
encounters the ridge, but it`s strong enough to force weak low level
cyclogenesis over the Plains, thus enhancing south-southwest flow
and moisture return over the Midwest Thursday night into Friday.
Deterministic guidance develops convection Friday afternoon over
eastern Nebraska and Kansas into northwest Missouri and Iowa, then
moves the storms east into the evening.  Storms will likely be
weakening as they move into our area Friday night with the loss of
daytime heating and overall weaker instability over the Mid
Mississippi Valley.

Rain chances continue as the short wave aloft migrates east and
pushes a weak cold front into northern Missouri and central Illinois
Saturday.  Then, the southern stream upper low left over from the
earlier trough fracture drifts northeast into the Plains on Sunday
bringing more moisture and instability to the region.  The upper
pattern re-amplifies as this happens and another blocking ridge sets
up over the Ohio Valley and Great Lakes which slows and nearly stops
the wave over the Midwest. The majority of LREF members (60-75%)
produce precipitation at some point Sunday through Tuesday, primarily
during the daytime hours which points toward diurnal showers and
thunderstorms.  However the cluster analysis also shows variance in
the amplitude of the wave as well as the position of the blocking
downstream ridge, so there is still some uncertainty in this
forecast.  Temperatures through the period look seasonably warm in
the mid to upper 80s, but afternoon convection could suppress
temperatures any day.

Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 454 AM CDT Wed Jun 3 2026

VFR flight conditions are expected to prevail through the period.
Light east-southeast winds will turn to the southeast and then to
the south by early Thursday morning.

Carney

&&

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

$$

WFO LSX