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000
FXUS63 KFSD 121545
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1045 AM CDT WED JUN 12 2013

.UPDATE...
ISSUED AT 1045 AM CDT WED JUN 12 2013

POST FRONTAL SHOWERS AND STORMS INTO MID AFTERNOON SHOULD STAY
NORTH AND EAST OF FSD WHERE BEST SUPPORT IS TO KEEP SOME
CONVECTION FIRING ALONG AN EVIDENT UPSTAIRS BOUNDARY. THE MOST
CONCENTRATED ACTIVITY SHOULD STAY NORTH OF OUR FORECAST AREA. HAVE
UPDATED TO SHOW THAT DECREASE IN PRECIPITATION MENTION. CLOUDS AT
SEVERAL LEVELS WILL CONTINUE INTO EARLY AFTERNOON...THEN SKIES
SHOULD GRADUALLY CLEAR FROM THE WEST AND SOUTHWEST. TEMPERATURES
WILL CONTINUE TO BE TAMED BY COOLING AND SOME ADJUSTMENTS WILL BE
NEEDED ACCORDING TO THE STRENGTH OF THE COOLING AND THE TIMING OF
THE CLEARING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 508 AM CDT WED JUN 12 2013

TWO MAIN AREAS OF CONVECTION PRESENTLY ONGOING ACROSS THE CWA VERY
EARLY THIS MORNING. THE FIRST IS LOCATED THROUGH OUR SOUTHEASTERN
ZONES IN CONJUNCTION WITH A LEADING SHORTWAVE AHEAD OF MAIN WAVE...
WHERE CONVERGENCE ON THE NOSE OF THE LOW LEVEL JET IS MAXIMIZED.
THESE STORMS HAVE REMAINED TAME THROUGHOUT THE NIGHT WITH CAPPING
REMAINING ACROSS THE AREA. SECOND AREA OF CONVECTION POISED TO ENTER
OUR NORTHWESTERN ZONES OVER THE NEXT HOUR OR SO...THIS IN A FORM OF
LINE WHICH HAS BEEN MARCHING ACROSS SOUTH DAKOTA THROUGH THE NIGHT
AS THE MAIN WAVE TRACKS EASTWARD. THE SOUTHERN PORTION OF THE LINE
HAS WEAKENED THROUGH THE NIGHT WHERE CAPPING IS STRONGEST...AND WILL
CONTINUE TO WATCH THIS AREA WITH THE POSSIBILITY OF STRONG WINDS
WITH THIS LINE...THOUGH SEVERE REPORTS HAVE BEEN FAR AND FEW IN
BETWEEN THROUGH THE NIGHT. CONFIDENCE ON EVOLUTION AND TIMING OF
CONVECTION THROUGH THE DAY IS RATHER LOW...WITH NOT A SINGLE MODEL
HANDLING CURRENT CONVECTION WELL...THOUGH THINK BETTER CHANCES OF
CONVECTION WILL REMAIN NORTH OF INTERSTATE 90 ALONG THE NORTHERN
EDGE OF THE CAP. DOES APPEAR TO BE A GENERAL TREND TO THE EAST
THROUGH THE DAY AS THE UPPER LEVEL WAVE TRACKS EASTWARD...WITH
CONVECTION TAPERING OFF FROM WEST TO EAST INTO THE AFTERNOON. THERE
WILL BE COOLER AIR ADVECTING IN BEHIND THE WAVE...AND THIS WILL BE
REFLECTED IN HIGHS A GOOD 10 DEGREES COOLER THAN YESTERDAY...TOPPING
OUT IN THE MID TO UPPER 70S ACROSS THE AREA.

QUIET WEATHER SHOULD PREVAIL TONIGHT AS UPPER LEVEL AND SURFACE RIDGE
BEGIN TO MOVE INTO WESTERN PARTS OF THE AREA. WITH CLEARING SKIES AND
LIGHT WINDS TONIGHT...WOULD NOT BE SURPRISED TO SEE SOME PATCHY FOG
DEVELOP GIVEN THE WET GROUND OF LATE. HOWEVER...RELATIVELY DRIER AIR
WORKS SOUTHWARD INTO THE AREA BEHIND THE DEPARTING FRONT...SO DO NOT
EXPECT ANYTHING TOO WIDESPREAD OR DENSE AND HAVE NOT MENTIONED IN THE
FORECAST AT THIS TIME. SHOULD BE A FAIRLY COMFORTABLE NIGHT WITH LOWS
IN THE LOWER TO MID 50S.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 508 AM CDT WED JUN 12 2013

RIDGE AXIS SHIFTS SLOWLY EASTWARD THROUGH THE CWA THURSDAY...WITH
RETURN SOUTHEASTERLY FLOW DRAWING WARMER AND MORE HUMID AIR BACK INTO
WESTERN PARTS OF THE FORECAST AREA THURSDAY NIGHT/FRIDAY. INCREASING
THUNDERSTORM CHANCES WILL ACCOMPANY THE WARMTH/HUMIDITY...AS SUBTLE
MID-UPPER LEVEL WAVES SLIDE INTO THE AREA IN SOUTHWEST FLOW ALOFT.
SLIGHT CHANCE OF THUNDERSTORMS IN OUR SOUTHWEST THURSDAY EVENING AS
LOW LEVEL JET BEGINS TO INCREASE INTO CENTRAL SD. HOWEVER BEST CHANCE
THURSDAY NIGHT LOOKS TO HOLD OFF UNTIL AFTER 06Z...AS ELEVATED WARM
FRONT LIFTS NORTHEAST THROUGH THE WESTERN/CENTRAL PORTIONS OF THE
FORECAST AREA. NOT EXPECTING SEVERE STORMS BUT STEEP MID LEVEL LAPSE
RATES LEADING TO STOUT ELEVATED CAPE VALUES...SO SMALL HAIL POSSIBLE
WITH THE MORNING ELEVATED ACTIVITY.

BETTER SEVERE CHANCE MOVES ACROSS THE AREA FRIDAY AFTERNOON/EVENING AS
DEEP LAYER SHEAR INCREASES WITH APPROACHING UPPER TROUGH AND SURFACE
BOUNDARY PUSHING INTO OUR WESTERN CWA. EXPECT LATE NIGHT ELEVATED
ACTIVITY TO PUSH EAST OF THE AREA BY MIDDAY...ALLOWING FOR DECENT
HEATING AHEAD OF THE BOUNDARY IN THE WEST. GFS/NAM BOTH INDICATING
0-6KM BULK SHEAR OF 40-50KTS WITH CONSERVATIVE CAPE VALUES ON THE
ORDER OF 1500-3000J/KG WITH DECREASING CIN JUST AHEAD OF THE BOUNDARY.
SHOULD SEE SCATTERED STORMS DEVELOPING ALONG/WEST OF THE JAMES VALLEY
BY LATE AFTERNOON...WITH STORMS REMAINING ORGANIZED AS THEY MOVE EAST
INTO MN/IA FRIDAY NIGHT. LARGE HAIL/DAMAGING WINDS APPEAR TO BE THE
PRIMARY THREATS FROM POTENTIAL SUPERCELLS FRIDAY AFTERNOON/EVENING...
THOUGH ISOLATED TORNADOES POSSIBLE WITH STORMS THAT DEVELOP ON THE
BOUNDARY. AS THE STORMS SHIFT EASTWARD OVERNIGHT...EXPECT THEM TO
BECOME MORE ELEVATED WITH LARGE HAIL A GREATER THREAT.

CHANCE OF STORMS WILL LINGER INTO THE WEEKEND...WITH FAVORED LOCATION
DEPENDENT ON WHERE RESIDUAL BOUNDARIES END UP. GFS HOLDS THE BOUNDARY
ACROSS THE SOUTHEAST CORNER OF OUR FORECAST AREA SATURDAY AFTERNOON
WHILE OTHER MODELS PUSH IT A LITTLE FARTHER SOUTHEAST. WITH UPPER
LEVEL JET JUST NORTH OF THE AREA AND VERY MOIST LOW LEVEL AIR ALONG
AND SOUTH OF THE BOUNDARY...CONTINUE TO SEE STRONG SHEAR AND HIGH
CAPE VALUES SUPPORTIVE OF ISOLATED SEVERE STORMS. HOWEVER WITH THE
UNCERTAINTY REGARDING BOUNDARY LOCATION...WILL NOT HIGHLIGHT THREAT
IN THE HWO AT THIS TIME.

SUNDAY EVEN MORE MUDDLED WITH LITTLE AGREEMENT AMONG THE LONGER RANGE
MODELS. BROAD CONSENSUS SHOWS UPPER TROUGH AND ASSOCIATED SURFACE LOW
IN NORTHERN MINNESOTA/SOUTHWEST ONTARIO WITH WEAK SURFACE FRONT INTO
WESTERN IOWA/SOUTHEAST NEBRASKA. WILL CARRY ONLY LOW POPS FOR THIS
PERIOD AS MAIN UPPER SUPPORT LOOKS TO BE NORTH OF THE AREA...ALTHOUGH
ECMWF WOULD INDICATE GREATER POTENTIAL AND WILL HAVE TO WATCH.

DRIER SURFACE HIGH THEN SETTLES INTO THE REGION FOR EARLY NEXT WEEK
AND WILL KEEP MONDAY/TUESDAY DRY. TEMPERATURES THROUGH THE LONGER
RANGE LOOK NEAR NORMAL WITH HIGHS IN THE UPPER 70S-LOWER 80S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 615 AM CDT WED JUN 12 2013

CONFIDENCE IN CONVECTIVE DEVELOPMENT AND TIMING LOW TODAY WITH
MODELS HANDLING PRESENT CONVECTION POORLY. THAT BEING
SAID...BETTER CHANCE OF CONVECTION WILL BE THROUGH SOUTHWESTERN
MINNESOTA DURING THE MORNING...THEN GENERALLY EAST OF INTERSTATE
29 DURING THE AFTERNOON BEFORE TAPERING OFF BY EVENING. THINK
THAT MOST OF THE CONVECTION WILL REMAIN EAST OF TAF SITES...THOUGH
DID INCLUDE TEMPO GROUPS FOR THUNDER AT KHON AND KFSD DURING THE
LATE MORNING. NORTH/NORTHEASTERLY WINDS WILL BE GUSTY INTO THE
AFTERNOON BEFORE DYING OFF THIS EVENING.


&&

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

$$

UPDATE...
SHORT TERM...JH/JM
LONG TERM...JH
AVIATION...JM