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000
FXUS63 KFSD 200920
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
420 AM CDT MON MAY 20 2013

.SHORT TERM...(TODAY)
ISSUED AT 417 AM CDT MON MAY 20 2013

STACKED UPPER LOW WILL MAKE LITTLE HEADWAY EAST WITH SYSTEM CUTOFF
FROM UPPER FLOW.  COLD FRONT LOCATED IN THE JAMES RIVER VALLEY...AND
WITH UPPER WAVE MOVING THROUGH...SERVING AS A FOCUSING MECHANISM FOR
SHOWERS AND THUNDERSTORMS. FOCUS FOR SHOWERS AND THUNDERSTORMS
SHOULD LIFT NORTH THROUGH THE MORNING HOURS FOLLOWING THE UPPER
WAVE.  THEREAFTER...ISENTROPIC LIFT SHOULD LEAD TO WIDESPREAD
SHOWERS BEHIND THE FRONT...WITH SCATTERED THUNDERSTORMS DEVELOPING
IN THE WARM SECTOR AHEAD OF THE FRONT. CAPE IS FAIRLY WEAK AROUND
1000 J/KG...BUT NICE VEERING PROFILE MAY BE JUST ENOUGH TO ALLOW
STRONGER STORMS EAST OF THE FRONT TO ORGANIZE ENOUGH TO PRODUCE
MARGINALLY SEVERE HAIL THIS AFTERNOON.  FORECAST HIGHS APPEARED TO
BE FAIRLY REASONABLE AND ALTERED LITTLE.

.LONG TERM...(TONIGHT THROUGH SUNDAY)
ISSUED AT 417 AM CDT MON MAY 20 2013

ACTIVE WEATHER PATTERN PERSISTS THROUGHOUT THE UPCOMING WEEK WITH
ONLY A BRIEF PAUSE IN THE ACTION AROUND MID WEEK. EARLY WEEK WILL
REMAIN UNDER THE INFLUENCE OF THE VERY LARGE AND SLOW MOVING UPPER
LOW WHICH GRADUALLY WOBBLES EAST-SOUTHEAST INTO THE GREAT LAKES
THROUGH WEDNESDAY.

WITH THE UPPER LOW CENTER TEETERING NEAR THE FORECAST AREA...IT
LOOKS LIKE THE BEST POTENTIAL FOR PRECIPITATION DURING THE PERIOD
WILL BE ACROSS OUR NORTHWESTERN THIRD WHERE TROWALING WILL LIKELY
SET UP ACROSS CENTRAL AND NORTHEAST SOUTH DAKOTA. THIS WILL LIKELY
PLACE MUCH OF THE CENTRAL AND EASTERN FORECAST AREA IS THE DRY
SECTOR OF THE LOW...ESPECIALLY AS THE SYSTEM SINKS SOUTHWARD A BIT
LATE TONIGHT AND TUESDAY. IT IS STILL A BIT DIFFICULT TO REALLY
PINPOINT POPS WITH SEVERAL WAVES EXPECTED TO ROTATE AROUND THE LOW
AND CREATE OCCASIONAL PERIODS OF MORE PERSISTENT SHOWERS...SO HAVE
OPTED TO KEEP HIGH CHANCES AND LIKELIES GOING IN THE WEST WHILE
CENTRAL AND EAST WILL SEE MORE SCATTERED TO ISOLATED SHOWERS. BY
TUESDAY NIGHT AND WEDNESDAY...THE LOW PULLS FURTHER AWAY FROM THE
FORECAST AREA AS IT GRADUALLY WEAKENS. SCATTERED SHOWERS WILL
PERSIST OVERNIGHT AND TAPER OFF FROM WEST TO EAST WEDNESDAY.
TEMPERATURES WILL REMAIN COOL UNDER MOSTLY CLOUDY SKIES WITH HIGHS
MAINLY IN THE UPPER 50S AND LOWER 60S.

UPPER LEVEL RIDGING BUILDS INTO THE HIGH PLAINS WEDNESDAY AFTERNOON
WHILE SURFACE HIGH PRESSURE SINKS SOUTHWARD WEDNESDAY NIGHT. RETURN
FLOW DEVELOPS ON THURSDAY WHICH...ALONG WITH CLEARING SKIES WILL
WARM TEMPERATURES BACK INTO THE MID 60S TO NEAR 70. SOUTHWEST UPPER
LEVEL FLOW WILL BRING A RETURN TO THE ACTIVE WEATHER PATTERN FRIDAY
THROUGH THE WEEKEND AS SEVERAL WAVE TRACK INTO THE AREA. MODELS
SHOWING UNCERTAINTY IN THE TIMING OF THE WAVES BUT IT DOES LOOK LIKE
THE STEADY INFLUX OF MOISTURE AND WAVES IS ENOUGH TO KEEP MENTION OF
SCATTERED THUNDERSTORMS EACH PERIOD THROUGH THE WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 1045 PM CDT SUN MAY 19 2013

AREA OF SHOWERS AND THUNDERSTORMS CONTINUES TO WEAKEN ACROSS THE
AREA THIS EVENING. THERE COULD BE SOME ISOLATED THUNDER THAT LINGERS
THROUGH THE NIGHT...BUT FOR NOW WILL KEEP IT JUST SHOWERS IN THE
TAFS...AND EVEN THE SHOWER ACTIVITY SHOULD BE SCATTERED AND PRETTY
LIGHT. MAINLY VFR CONDITIONS THIS EVENING...ALTHOUGH SOME MVFR
STRATUS AND FOG IS SCATTERED ABOUT. LATER TONIGHT INTO TOMORROW
MORNING LOOKS LIKE A BETTER CHANCE OF MVFR STRATUS FORMING AS SOME
SOME WEAK LOW LEVEL COLD AIR ADVECTION OVERRUNS OUR MOIST LOW
LEVELS. THE CLOUD BASES SHOULD TEND TO LIFT INTO THE VFR RANGE BY
LATE MORNING OR EARLY AFTERNOON...ESPECIALLY EAST OF THE JAMES
RIVER. TO THE EAST...RAIN CHANCES LOOK ON THE LOW SIDE THROUGH THE
DAY TOMORROW...ALTHOUGH THERE COULD BE SOME ISOLATED
ACTIVITY...ESPECIALLY ACROSS NORTHWEST IOWA. COULD EVEN BE A RUMBLE
OF THUNDER THERE DURING THE AFTERNOON. TO THE WEST OF THE
JAMES...LOWER CIGS AND SHOWERS MAY VERY WELL LINGER FOR MOST OF THE
DAY.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...
LONG TERM...
AVIATION...CHENARD