Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 010417
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1117 PM CDT MON AUG 31 2015

.UPDATE:
ISSUED AT 858 PM CDT MON AUG 31 2015

THE ISOLATED SHOWERS/STORMS ACROSS PARTS OF SOUTHEAST AND EAST
CENTRAL MO AND SOUTHWEST IL HAVE DISSIPATED THIS EVENING DUE TO THE
LOSS OF DAYTIME HEATING WITH MUCH OF THE CONVECTIVE CLOUD DEBRIS
ALSO DISSIPATING AS WELL. MAY HAVE SOME NOCTURNAL DEVELOPMENT OF
CONVECTION LATE TONIGHT/EARLY TUESDAY MORNING ACROSS PARTS OF
SOUTHWEST IL...OVER THE EASTERN PORTION OF THE FORECAST AREA JUST
WEST OF AN UPPER LEVEL LOW. THE LATEST HRRR MODEL RUN DOES
GENERATE CONVECTION IN THIS AREA...ALTHOUGH THE LATEST NAM MODEL
RUN DOES NOT HAVE ANY QPF IN THIS AREA LATE TONIGHT AS THE
PREVIOUS RUN OF THIS MODEL DID. WILL JUST KEEP THE SLIGHT CHANCE
POPS OVER THE EASTERN PORTION OF THE FORECAST AREA BEGINNING AT
11Z TUESDAY. A MILD MUGGY NIGHT CAN BE EXPECTED WITH SOUTH-
SOUTHEASTERLY SURFACE WINDS AND HIGH SURFACE DEW POINTS. THERE MAY
BE SOME PATCHY LIGHT FOG/HAZE. THE LOWS TONIGHT SHOULD BE SIMILAR
TO THE PREVIOUS NIGHT AND ABOUT 5 TO 10 DEGREES ABOVE NORMAL FOR
EARLY SEPTEMBER.

GKS

&&

.SHORT TERM:  (THROUGH LATE TONIGHT)
ISSUED AT 304 PM CDT MON AUG 31 2015

THUNDERSTORMS THAT PRODUCED HEAVY RAINFALL OVER THE EASTERN CWA THIS
MORNING DISSIPATED WITH THE LOSS OF THE WEAK LOW LEVEL MOISTURE
CONVERGENCE ON THE WEST SIDE OF THE UPPER LEVEL LOW CURRENT CENTERED
OVER INDIANA.  MORE RECENTLY...ATMOSPHERE HAS BECOME VERY UNSTABLE
WITH MLCAPES OF 2000-3000 J/KG WITH LITTLE CIN.  SHEAR AXIS HAS
MOVED DOWN INTO SOUTHERN MISSOURI...SO THINK BEST CHANCE FOR
THUNDERSTORMS WILL BE OVER THE EASTERN OZARKS...PARTICULARLY SINCE
THAT IS TRADITIONALLY WHERE OROGRAPHIC LIFT HAS HELPED GENERATE LATE
AFTERNOON/EARLY EVENING THUNDERSTORMS IN THE PAST.  WOULD EXPECT ANY
CONVECTION TO DIMINISH WITH LOSS OF DAYTIME HEATING.

ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE ONCE AGAIN LATE TONIGHT
OVER THE EASTERN CWA AS BOTH THE NAM AND GFS ARE POINTING TOWARD TO
SOME WEAK 925-850MB MOISTURE CONVERGENCE DEVELOPING ONCE AGAIN ON
THE WEST SIDE OF THE UPPER LEVEL LOW.  WILL GO WITH A SLIGHT CHANCE
OF THUNDERSTORMS LATE TONIGHT THROUGH TOMORROW MORNING.

BRITT

.LONG TERM:  (TUESDAY THROUGH NEXT MONDAY)
ISSUED AT 304 PM CDT MON AUG 31 2015

(TUESDAY THROUGH THURSDAY)

PLAN TO GO WITH A DRY FORECAST FROM TUESDAY AFTERNOON THROUGH
THURSDAY AS FORCING FOR THUNDERSTORMS LOOKS WEAK AS UPPER LOW MOVES
EAST AND UPPER RIDGE AXIS BUILDS OVER THE AREA WHICH SHOULD SUPPRESS
THUNDERSTORM DEVELOPMENT.  DON`T EXPECT MUCH CHANCE IN THE WARM AND
HUMID CONDITIONS. BASED HIGHS ON MIXING DOWN 850MB TEMPERATURES
WHICH ARE CLOSE TO +20C.

(FRIDAY THROUGH MONDAY)

FORECAST STILL LOOKS ON TRACK FOR MAINLY DRY WEATHER EARLY ON FOR
THE HOLIDAY WEEKEND AS THE UPPER LEVEL RIDGE AXIS MOVES OVER THE
AREA WHICH WILL SUPPRESS THUNDERSTORMS ACTIVITY ON FRIDAY AND
SATURDAY.  THIS RIDGE AXIS WILL BEGIN TO BREAK DOWN BY SUNDAY...SO
WILL KEEP THE SLIGHT CHANCE OF THUNDERSTORMS OVER NORTHEAST MISSOURI
ON SUNDAY.  WILL GO WITH A WIDER CHANCE OF THUNDERSTORMS ON LABOR
DAY AS BOTH THE GFS AND ECMWF SHOW THE RIDGE AXIS MOVING SOUTH OF
THE AREA AT THE SAME TIME A COLD FRONT ENTERS THE AREA FROM THE
NORTH.  STILL WENT ABOVE NORMAL THROUGH THE HOLIDAY WEEKEND AS WE
WILL STAY IN THE SAME WARM AND HUMID AIRMASS UNTIL THE COLD FRONT
MOVES THROUGH.

BRITT

&&

.AVIATION:  (FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1105 PM CDT MON AUG 31 2015

WEAK UPPER LOW/SHEAR AXIS WILL BECOME CENTERED OVER INDIANA BY
MIDDAY TUESDAY. SUSPECT THAT WILL KEEP MOST OF THE TSRA DEELOPMENT
EAST OF THE TERMINALS. WHILE A ISOLATED STORM POSSIBLE, NO REASON
TO PUT IT IN THE FORECAST. PATCHY FOG OVERNIGHT, BASICALLY A
PERSISTENCE FORECAST.

SPECIFICS FOR KSTL: VFR DRY FORECAST CONTINUES. HIGH PRESSURE
BEGINS BUILDING THUS THE THE ISOLATED AFTERNOON THUNDERSTORMS WILL
BECOME EVEN MORE ISOLATED. WOULD NOT BE SURPRISED TO SEE SOME
MORNING FOG/HAZE START APPEARING THE NEXT COUPLE OF DAYS.

JPK

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX



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