Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 300140
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
840 PM CDT SAT AUG 29 2015

.UPDATE:
ISSUED AT 838 PM CDT SAT AUG 29 2015

NO BIG CHANGES TO THE FORECAST. VERY ISOLATED SHOWERS CONTINUE TO
PERCULATE ACROSS THE CENTER OF THE CWA NEAR A SHEAR AXIS/WEAK
FRONT. THIS WILL PROBABLY CONTINUE MOST OF THE NIGHT AS A WEAK LOW
LEVEL JET DEVELOPS AND AIDS THE LIFT OVERHEAD.

CVKING

&&

.SHORT TERM:  (THROUGH LATE TONIGHT)
ISSUED AT 333 PM CDT SAT AUG 29 2015

SHOWERS HAVE MOVED OUT OF THE CWA FOR THE MOMENT AS WATER VAPOR
IMAGERY IS CURRENTLY SHOWING THAT A WEAK UPPER LOW IS MOVING EAST
ACROSS SOUTHEAST MISSOURI. THERE IS ALSO A SHORTWAVE TROUGH
EXTENDING FROM THE GREAT LAKES INTO FAR NORTHEAST MISSOURI AND
A VORT MAX OVER SOUTHWEST MISSOURI THAT IS MOVING EASTWARD. THE
RAP SHOWS SOME WEAK ASCENT ALONG THE TROUGH AXIS AS IT MOVES EAST
SOUTHEAST THIS EVENING ACROSS NORTHEAST MISSOURI AND WEST CENTRAL
ILLINOIS WHILE THERE IS ALSO SOME INCREASED ASCENT ACROSS AREAS
SOUTH OF I-70 ASSOCIATED WITH THE VORT MAX. IN ADDITION...THE RAP
IS SHOWING SOME INCREASE IN LOW LEVEL MOISTURE CONVERGENCE
ASSOCIATED WITH THE VORT MAX. WILL GO WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS OVER THE SOUTHEASTERN HALF OF THE CWA THIS
EVENING...WITH LESSENING CHANCES OVERNIGHT AS THE MOISTURE
CONVERGENCE WEAKENS AND MOVES OFF TO THE EAST.

BRITT

.LONG TERM:  (SUNDAY THROUGH NEXT SATURDAY)
ISSUED AT 333 PM CDT SAT AUG 29 2015

(SUNDAY THROUGH TUESDAY)

THE UPPER LEVEL TROUGH AXIS WILL BE SLOW TO MOVE OUT OF THE AREA AS
AN UPPER LEVEL RIDGE BUILDS OVER IT ACROSS THE UPPER MIDWEST ON
SUNDAY AND MONDAY. THIS WILL KEEP THE UPPER LEVEL TROUGH OVER THE
AREA AT LEAST THROUGH SUNDAY WHICH WILL SUPPLY SOME LIFT OVER THE
AREA THROUGH THE DAY. RUNS OF THE CAMS SUGGEST THAT CONVECTIVE
COVERAGE WILL BE SCATTERED DURING THE DAY SO HAVE UPPED POPS TO 30
PERCENT IN MOST AREAS. GFS AND NAM BEGIN TO BECOME MORE UNCERTAIN
ON LOCATION OF TROUGH AXIS BY MONDAY...SO WENT WITH DRY FORECAST
THOUGH IT IS POSSIBLE THAT THE TROUGH AXIS COULD WELL END UP IN
SOUTHERN MISSOURI AND BRING THE SOUTHERN CWA A SLIGHT CHANCE OF
THUNDERSTORMS. WILL ALSO KEEP TUESDAY DRY FOR NOW...THOUGH THE NAM
WOULD BRING A WEAK SHORTWAVE TROUGH ACROSS THE AREA DURING THE DAY
THAT MAY BEAR WATCHING.

WENT ON THE WARM SIDE OF GUIDANCE THROUGH THE PERIOD AS WE WILL BE
MIXING DOWN AIR FROM THE 800-850MB LAYER...PARTICULARLY ON MONDAY
AND TUESDAY WHICH HAS TEMPERATURES AROUND +20C WHICH FAVORS
TEMPERATURES GOING BACK ABOVE NORMAL.

(WEDNESDAY THROUGH NEXT SATURDAY)

AREA WILL BE MAINLY DRY LATE WEEK INTO NEXT WEEKEND AS UPPER
RIDGE AXIS THAT EXTENDS FROM THE CENTRAL PLAINS INTO THE UPPER
MIDWEST ON THURSDAY WILL SHIFT OVER MISSOURI AND ILLINOIS BY
SATURDAY. CONSEQUENTLY...SURFACE RIDGE WILL LINGER OVER MISSOURI
AND ILLINOIS THROUGH THE MEDIUM RANGE PERIOD. TEMPERATURES WILL BE
AT OR SLIGHTLY ABOVE NORMAL AS WE GO INTO THE HOLIDAY WEEKEND AS
850MB TEMPERATURES REMAIN CLOSE TO +20C.

BRITT

&&

.AVIATION:  (FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 624 PM CDT SAT AUG 29 2015

SPECIFICS FOR KUIN, KCOU: SH/TS HAVE DEVELOPED NEAR KUIN,
THEREFORE WILL MAINTAIN VCTS FOR THE FIRST HOUR OF THE TAF
PERIOD. LOSS OF DAYTIME HEATING SHOULD END THE SH/TS CONCERN FOR
THE REST OF THE EVENING. NEXT FORECAST ISSUE IS EITHER FOG OR
STRATUS OVERNIGHT. SINCE THERE HAS BEEN LITTLE CLEARING OF THE
EXISTING CLOUD DECK TODAY, STRATUS APPEARS MORE LIKELY THAN FOG.
WINDS WILL REMAIN LGT/VAR OVERNIGHT INVOF A DECAYING FRONTAL
BOUNDARY, THEN BECOME SOUTHERLY TOMORROW MORNING.

SPECIFICS FOR KSTL, KSUS, KCPS: SH/TS HAVE DEVELOPED NORTHWEST OF
THE ST. LOUIS METRO AREA, THEREFORE IT SEEMS PRUDENT TO KEEP VCTS
IN THE TAFS AT KSUS AND KSTL FOR THE NEXT HOUR. LOSS OF DAYTIME
HEATING SHOULD END THE SH/TS CONCERN FOR THE EVENING. NEXT ISSUE
IS EITHER FOG OR STRATUS OVERNIGHT. ATTM IT LOOKS LIKE MVFR TO IFR
STRATUS IS MORE LIKELY TO OCCUR NORTH AND WEST OF THE TERMINALS,
BUT THE POTENTIAL WILL NEED TO BE REASSESSED AT THE 06Z ISSUANCE
BASED ON SATELLITE TRENDS.

KANOFSKY

&&

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

$$

WFO LSX



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