554
FXUS63 KLSX 272328
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
628 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 00z TAFs through 00z Tuesday Evening)
Issued at 628 PM CDT Mon May 27 2024

Sub-severe thunderstorms will continue to move southeast of the St.
Louis metro area this evening, weakening with time. Isolated
thunderstorms in northeast Missouri may impact KUIN, but will more
likely split the terminal. Thunderstorms have had a history of
producing wind gusts of up to 43 kts and, upon a direct hit, IFR
visibilities. Convective activity is expected to diminish this
evening. Otherwise, winds will decrease to <10 kts tonight before
becoming gusty (20-25 kts) tomorrow afternoon. There is another
slight chance of scattered showers and thunderstorms in northeast
Missouri to south central Illinois tomorrow afternoon, but
confidence in exact location is too low to mention at this
issuance.

Jaja

&&

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

$$

WFO LSX