882
FXUS63 KLSX 170901
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
401 AM CDT Mon Jun 17 2024

.KEY MESSAGES...

- Today will be another hot day with heat index values ranging from
95-103. There is a chance for isolated to scattered afternoon
showers and thunderstorms along and south of the I-44 corridor (20-
40%).

- Summer-like temperatures will continue Tuesday through the
  weekend with periodic shower and thunderstorm chances (20-30%).


&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 349 AM CDT Mon Jun 17 2024

Water vapor imagery shows that mid-level ridging and high pressure
has begun to dominate the eastern CONUS with southerly low level
flow into the Mid-Mississippi River Valley. This deep southerly flow
favors warm and moist air to be transported into the Mid-Mississippi
River Valley through at least midweek.

There is agreement in the deterministic guidance that a weak mid-
level vorticity maximum, currently seen in water vapor imagery over
northeast Louisiana, will round the mid-level high and traverse
across far southeast Missouri and southern Illinois this afternoon.
With the abundant available low-level moisture, this area will be
the focus of diurnally-driven scattered showers and thunderstorms
this afternoon and evening. Deterministic model soundings are
indicating DCAPE values 1000+ J/kg, SBCAPE values between 2000-3000
J/kg, and mid-level lapse rates around 6 C/km. This favors pulse
thunderstorms capable of gusty winds and heavy downpours.

Today will be another hot and humid day amidst deep southerly flow,
however not as hot as yesterday. Dewpoints across the area are
forecast to be in the upper 60s - low 70s. These high dewpoints
combined with highs in the upper 80s - mid 90s will keep heat index
values between 95-103 degrees area wide. The main factor for
temperatures not being as hot as yesterday is that guidance is
hinting at increased mid-level cloud cover with the passing
vorticity maximum. Another factor that would keep high temperatures
on the "cooler" side is the shower and thunderstorm potential across
southeast Missouri and southern Illinois. Should an area see a
shower and thunderstorm, expect for high temperatures to be
suppressed. Despite the slightly less warm temperatures today, it
is important to still take necessary heat precautions such as
taking frequent breaks if outside and drinking plenty of water.

Tuesday will be another hot day with highs in the mid 80s - low 90s
in the persistent deep southerly flow. Deterministic guidance is in
agreement that additional weak vorticity maxima will round the mid-
level high Tuesday afternoon and evening and be the focus for
another chance (20-30%) of diurnal showers and thunderstorms.
Similar to today, areas that see a shower or thunderstorm could see
highs on the "cooler" side.

MMG/Glass

&&

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 349 AM CDT Mon Jun 17 2024

There is agreement among guidance that hot temperatures will
continue Wednesday onward as the mid-level high retrogrades westward
through Saturday. As it shifts westward, there will be periodic
chances (20-30%) of afternoon showers and thunderstorms associated
with the rounding of additional vorticity maxima around the high.
The areas that will see these chances for convection will be across
north-central and northeast Missouri on Wednesday. Shower and
thunderstorm chances diminish even more on Thursday and Friday as
surface high pressure dominates the Mid-Mississippi River Valley and
favors dry conditions. Dewpoints will remain in the 60s through
the end of the work week and with convection chances decreasing
Thursday and Friday, temperatures will rebound into mid to upper
90s area wide.

By late Saturday, ensemble guidance is in consensus that a mid-level
trough will traverse across the Upper Mississippi River Valley.
As it propagates east-southeastward into Sunday, a surface cold
front will move across the region and be the focus for showers and
thunderstorms. There is uncertainty in the exact timing of
convection as there are timing and amplitude differences amongst
deterministic guidances of the trough and thus the cold frontage
passage.

MMG/Glass

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1048 PM CDT Sun Jun 16 2024

Light winds expected overnight under continued mostly clear sky.
Winds pick up a bit out of the south Monday morning with some
afternoon cumulus expected as well. Winds don`t die off as much
Monday night but VFR should continue.

Kimble

&&

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

$$

WFO LSX