276
FXUS63 KLSX 061919
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
219 PM CDT Thu Jun 6 2024

.KEY MESSAGES...

- Dry weather is expected to continue through tomorrow before a chance
  of showers and thunderstorms returns late Friday night into
  Sunday. The greatest chance (60-80%) is now late Friday night
  into Saturday morning across much of the area.

- Temperatures will remain at or below normal through early next
  week.

&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 214 PM CDT Thu Jun 6 2024

We`re seeing another dry afternoon as we are in deep northwest flow
between a deep low over Ontario and a large high over the
southwestern CONUS. There is a area of showers and scattered
thunderstorms over southwest Missouri, but it will continue to move
to the southeast and away from the CWA.  Our dry weather will
continue through early Friday evening as the high currently over the
Plains will move east across the area.  There has been a consistent
signal in the models the past two days that the MCS will develop
over the Plains and move east into Missouri on Friday night. The
HREF is showing a low level jet developing over eastern Kansas by
Friday evening with MUCAPES over 1000 J/kg which will likely help
initiate a MCS over eastern Kansas/southwest Nebraska/western
Missouri late in the evening or overnight on Friday. Compared to
past runs, this initiation is a bit farther north and will likely
move into at least the western parts of the CWA after midnight on
Friday night. There is some potential for a few strong storms
given initial amounts instability and shear, but the airmass it
will be moving into over eastern Missouri late Friday night will
be increasingly stable. There may be some areas that may see
locally heavy rainfall as PWATS will be near 1.8" per the LREF,
but this system will also be fairly progressive which will cutback
on the overall potential.

Temperatures will drop below normal tonight with the dry air and
good radiation cooling.  Temperatures will climb back above normal
on Friday with a sunny sky and 850mb temperatures climbing to around
15C.

Britt

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 214 PM CDT Thu Jun 6 2024

The latest runs of the NAM/GFS/ECMWF has the MCS farther north
across the heart of the CWA on Saturday morning. While there will be
impressive deep layer shear, it will likely weaken as it will be
encountering less instability and a veering low level jet as it
moves east southeast.  How quickly this MCS exits the area will
determine how quickly we will be able to destabilize ahead of an
afternoon front that both the NAM/GFS are bringing southeast through
the area.  If the MCS is progressive, both the NAM/GFS are showing
MLCAPES in the 1000-2000 J/kg range with deep layer shear near 40
knots, so couldn`t rule out a few strong to severe storms with this
front. The front will then become elongated under the west-
northwesterly flow aloft just to the south of the CWA on Saturday
night and another MCS will develop and move along it late Saturday
night into Sunday morning. Will keep high chance or likely PoPs
for the scenario. The LREF is then showing the upper ridge and a
surface high moving across the area early next week which will
bring drier weather to the area early next week followed by an
upper trough and an attendant cold front dropping down out of the
northern Plains by the middle of next week which will bring a low
chance (20%) to parts of the area by Wednesday.

Temperatures will be close to normal on Saturday, but then fall a
bit below normal behind the cold front Sunday into Monday before
starting a warming trend through the middle of next week that will
approach 90 degrees by this time next week.  Confidence in the
warmup is trending higher as the deterministic NBM is siding toward
the 75th percentile of the NBM IQR at STL, COU, and UIN on Wednesday
and Thursday.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1209 PM CDT Thu Jun 6 2024

Dry and VFR conditions are expected through the period. Northwest
to west winds will gust above 20 knots this afternoon before
decreasing after sunset. Winds will pick up again tomorrow
afternoon at St. Louis.

Britt

&&

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

$$

WFO LSX