837
FXUS63 KLSX 271941
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
241 PM CDT Mon May 27 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms will be possible mainly
  along and north of I-70 through early this evening and again on
  Tuesday afternoon.

- Wednesday and Thursday is expected to be dry before an unsettled
  weather pattern brings a chance of showers and thunderstorms
  beginning Thursday night through the weekend. Temperatures will
  be close to normal.

&&

.SHORT TERM...  (Through Late Tuesday Night)
Issued at 238 PM CDT Mon May 27 2024

Scattered showers and thunderstorms have developed across north
central Missouri this afternoon and are moving to the east.  Expect
them to continue to move to the east along and north of I-70 as the
latest RAP is showing MLCAPES of around 1000 J/kg ahead of a subtle
shortwave trough.  Convection will likely diminish after after 00Z
with loss of daytime heating and as the shortwave moves off to the
east of the CWA.  We will see a second round tomorrow afternoon
across the northern CWA as NAM/GFS is showing another shortwave
moving across the Upper Midwest.  This weak ascent combined with
forecast SBCAPES of 500-1000 J/kg suggests the potential for a
slight chance of showers and thunderstorms.

Temperatures will be at or just be normal for late May through
Tuesday night as we will be in neutral or weak cold air advection.

Britt

&&

.LONG TERM...  (Wednesday through Next Monday)
Issued at 238 PM CDT Mon May 27 2024

Generally dry weather is expected mid-late week before the weather
becomes more active as we enter next weekend.  There is general
agreement between the global models and LREF that a upper trough
over Great Lakes will move east and off the East Coast at the same
time that a Great Plains ridge will move into the Midwest by Friday.
This will set up northwesterly flow aloft Wednesday into Thursday at
the same time a surface high moves across Missouri and Illinois. The
pattern will begin to change next weekend once the upper ridge moves
past the area and the pattern become quasi-zonal over the Midwest.
There is good agreement between the global models with timing and
strength of the lead shortwave on Friday night, but less so with
subsequent troughs that will move through the area into early next
week.  The LREF is showing that about 50 percent of it members
having rain on Friday night with at least some chance (20-30
percent) through the rest of next weekend.

Temperatures will be at are a bit below normal into Friday as winds
will have a north to east component which favor cooler weather
before turning out of the south over the weekend.  At the same time,
850mb temperatures will climb from around 10C to 15C.  I have higher
confidence mid-late week as the NBM IQR is 5 degrees or less
Wednesday through Friday before becoming larger under the zonal flow
over the weekend.

Britt

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1240 PM CDT Mon May 27 2024

Scattered showers and thunderstorms have developed over north
central Missouri and will move east southeast. This most likely
airport to be affected is UIN between 21-23Z, so have added a
VCTS. There is a low chance of JEF/COU to be affect between 19-21Z
and the St. Louis area terminals between 23-01Z, but chances are
too low to include at this time. Any of the heavier showers or
thunderstorms could produce MVFR or possible IFR ceilings and
visibilities in brief downpours. Winds will remain out of the
west to northwest.

Britt

&&

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

$$

WFO LSX