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000
FXUS63 KFSD 131055
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
555 AM CDT THU JUN 13 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 436 AM CDT THU JUN 13 2013

LOOKS TO BE A DECENT DAY ACROSS THE AREA AS A SURFACE RIDGE AXIS
PRESENTLY SITUATED THROUGH THE WESTERN HIGH PLAINS SLIDES TO THE
EAST. THIS WILL PLAY OUT WITH LIGHT WINDS THROUGH MUCH OF THE
DAY...PICKING UP A BIT AND TRANSITIONING TO SOUTHEASTERLY IN OUR
WEST LATER IN THE AFTERNOON ON THE BACKSIDE OF THE EXITING HIGH.
WILL ALSO HAVE MOSTLY SUNNY SKIES...GIVING WAY TO SOME INCREASE IN
MID AND HIGH CLOUDS IN OUR WEST LATER IN THE AFTERNOON WITH THE
APPROACH OF A SHORTWAVE INTO THE CENTRAL PORTIONS OF SOUTH DAKOTA
AND NEBRASKA. THINK THAT ANY POTENTIAL PRECIPITATION WITH THIS
FEATURE WILL REMAIN TO THE WEST OF OUR AREA INTO AT LEAST EARLY
EVENING. 850 MB TEMPERATURES LOOK TO WARM OVER YESTERDAY...YIELDING
AFTERNOON HIGHS IN THE MID 70S TO NEAR 80.

SHOULD START TO SEE ELEVATED CONVECTION DEVELOP LATE THIS EVENING AS
NARROW ZONE OF FAIRLY STRONG ISENTROPIC LIFT DEVELOPS ACROSS CENTRAL
PORTIONS OF FORECAST AREA AHEAD OF WARM FRONT AND WEAK ASSOCIATED MID
LEVEL WAVE. MODELS SIMILAR IN SHOWING THE LIFT FOCUSED ALONG/EAST OF
THE JAMES RIVER VALLEY...WITH MID LEVEL CAPE VALUES OF 500-1000J/KG
AND MINIMAL CIN AS WELL AS EFFECTIVE SHEAR OF 30-45KT. THIS COULD
PRODUCE ISOLATED MARGINAL SEVERE HAIL LATE TONIGHT AND WILL ADD
MENTION OF THIS POTENTIAL TO THE HWO.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 436 AM CDT THU JUN 13 2013

FRIDAY KIND OF A TRICKY DAY AS FAR AS SEVERE POTENTIAL...AS DEEP LIFT
FROM WARM ADVECTION/BROAD ISENTROPIC LIFT PERSISTS ACROSS THE EASTERN
CWA MUCH OF THE DAY. WARM ADVECTION ALOFT COMBINED WITH LIMITED SURFACE
HEATING DUE TO EXPECTED CLOUD COVER SHOULD STRENGTHEN CAP TO SURFACE
BASED CONVECTION ACROSS THE EAST MUCH OF THE DAY. HOWEVER...AT LEAST
SCATTERED ELEVATED STORMS LIKELY TO CONTINUE AND THESE STORMS WILL
HAVE PLENTY OF INSTABILITY TO WORK WITH ABOVE THE CAP...KEEPING A
THREAT OF ISOLATED SEVERE HAIL IN THE EAST THROUGH THE DAY. MID LEVEL
WAVE MOVES INTO THE AREA FRIDAY AFTERNOON...AND QUESTION IS WHETHER
THIS WAVE WILL BE STRONG ENOUGH TO BREAK THE AFOREMENTIONED CAP AND
ALLOW FULL DEPTH OF STRONG SHEAR TO BE UTILIZED. IF IT DOES SO...HIGH
CAPE AND STRONG SHEAR ACROSS THE WEST SUPPORTIVE OF SUPERCELLS...WITH
THREAT OF LARGER HAIL AND DAMAGING WINDS. GIVEN LOWER CONFIDENCE IN
THIS DEVELOPMENT...WILL STICK WITH LOW-MID RANGE CHANCE POPS IN THE
WESTERN CWA...WITH HIGHER POPS ACROSS THE EAST WHERE SCATTERED MID
LEVEL ACTIVITY EXPECTED TO BE MORE DOMINANT. HIGHS FRIDAY EXPECTED TO
VARY FROM MID 70S IN THE EAST...TO MID 80S NEAR THE SURFACE BOUNDARY
WEST OF THE JAMES RIVER.

FRIDAY NIGHT...SURFACE FRONT BECOMES SOMEWHAT ILL-DEFINED DUE TO
ONGOING CONVECTION...BUT APPEARS THAT UPPER WAVE TRIES TO DRAG THE
NORTHERN PORTION OF THE BOUNDARY EASTWARD INTO MINNESOTA WHILE THE
SOUTHERN END REMAINS ANCHORED BACK IN WESTERN KANSAS. WILL KEEP HIGH
POPS OVER THE SOUTHEAST PARTS OF THE CWA...ESPECIALLY FRIDAY EVENING
AS NAM/GFS SHOW CONTINUED LOW LEVEL MOISTURE TRANSPORT INTO NORTHWEST
IOWA AS LOW LEVEL FLOW VEERS TO THE SOUTHWEST AHEAD OF BOUNDARY. GEM
AND ECMWF NOT AS BULLISH WITH THIS...INSTEAD SHIFTING BETTER MOISTURE
EAST OF THE AREA AND KEEPING OUR CWA LARGELY DRY FRIDAY NIGHT. FOR
NOW WILL KEEP LIKELY POPS GOING ACROSS OUR EAST...BUT WILL HAVE TO
WATCH MODEL TRENDS ON EVOLUTION OF THIS SYSTEM AS COULD TURN OUT TO
BE A DRIER PERIOD THAN CURRENTLY INDICATED.

BY SATURDAY...GENERAL CONSENSUS SHOWS THE SURFACE BOUNDARY SOUTH OF
OUR CWA. HOWEVER 850MB FRONT LINGERS NEAR THE SOUTHEAST CORNER OF THE
FORECAST AREA AND DEEP LIFT PERSISTS IN RIGHT ENTRANCE REGION OF 90+
KT UPPER LEVEL JET ACROSS NORTHERN MINNESOTA. WITH THIS WILL KEEP A
CHANCE OF PRECIPITATION ACROSS NORTHWEST IOWA THROUGH THE DAY...WITH
CHANCES TAPERING QUICKLY TO THE NORTH OF KYKN-KMWM LINE AS DRIER AIR
PUSHES SOUTHWARD INTO THE AREA. SEVERE CHANCES CONDITIONAL ON STORM
DEVELOPMENT...THOUGH MODELS SHOWING 1000-2000J/KG SBCAPE ALONG WITH
DECENT DEEP LAYER SHEAR DUE TO STRONG WINDS ALOFT...SO COULD NOT RULE
OUT ISOLATED SEVERE STORMS. HIGHS SHOULD BE NEAR SEASONAL NORMAL IN
THE UPPER 70S-LOWER 80S.

WILL CONTINUE CHANCE POPS ACROSS MAINLY WESTERN/SOUTHERN PARTS OF THE
AREA SUNDAY/SUNDAY NIGHT AS STRONGER NORTHERN STREAM TROUGH SLIDES
THROUGH MINNESOTA. SOME QUESTION AS TO HOW EXTENSIVE PRECIP WILL BE
AS MOISTURE SOMEWHAT LACKING IN AREA OF WEAK SURFACE RIDGING BETWEEN
NORTHERN LOW PRESSURE IN SOUTHERN MANITOBA AND WEAKENING FRONTAL
BOUNDARY ACROSS THE CENTRAL PLAINS...AND MAY BE ABLE TO TRIM THESE
POPS FURTHER IF THE TREND TOWARD DRYING CONTINUES IN LATER MODEL
RUNS.

SURFACE RIDGING BECOMES MORE DOMINANT THROUGH THE EARLY PART OF NEXT
WEEK...KEEPING THE AREA DRY WITH SEASONAL TEMPERATURES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 549 AM CDT THU JUN 13 2013

VFR CONDITIONS THROUGH THE TAF PERIOD. MAY SEE SCATTERED
CONVECTION DEVELOP LATE TONIGHT...POSSIBLY EFFECTING KFSD AND KSUX
AFTER 06Z.

&&

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

$$

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