180 
FXUS63 KFSD 291104
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
604 AM CDT SUN JUN 29 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 433 AM CDT SUN JUN 29 2014

ELEVATED INSTABILITY CARE OF DECENT MID AND UPPER LEVEL LAPSE RATES 
HELPING DRIVE INCREASING THREAT FOR THUNDERSTORMS EARLY THIS 
MORNING. STRONG JET MAX SPREADING ACROSS NEBRASKA AIDING ON 
INCREASING SHEAR AS THE LOW LEVELS ARE BEGINNING TO RESPOND WITH 
INCREASED 925MB TO 850MB WINDS AND CONVERGENCE. OVERALL WHEN COUPLED 
WITH ELEVATED CAPE VALUES OF ABOUT 1500 J/KG AN EFFECTIVE BULK SHEAR 
OF CLOSE TO 40 KNOTS SHOULD SUPPORT ISOLATED SEVERE THUNDERSTORMS IN 
THE SOUTHERN CWA THROUGH MID MORNING. THE INSTABILITY THEN REMAINS 
LOCKED UP IN THE SOUTHERN CWA BUT AS THIS WAVE MOVES THROUGH THE LOW 
LEVEL CONVERGENCE WEAKENS QUITE A BIT SO POTENTIAL FOR NOT TOO MUCH 
ACTIVITY FROM LATE AFTERNOON INTO THE EARLY EVENING. HOWEVER THE 
WAVE WILL MOVE INTO THE AREA LATE EVENING AND THE LOW LEVEL FLOW 
INCREASES AND EXPECT STORMS TO STRENGTHEN AND EXPAND IN COVERAGE. A 
FEW SEVERE STORMS WOULD BE POSSIBLE AS WELL AS POCKETS OF HEAVY 
RAIN...ALTHOUGH WITH PRECIPITABLE WATER ABOUT 1.25 INCHES NOT 
EXPECTING WIDESPREAD PROBLEMS. TEMPERATURES SHOULD BE A BIT WARMER 
TODAY WITH A LOT LESS LOW CLOUD COVER SO AIMING FOR MAINLY 80 TO 85 
MOST SPOTS. LOWS TONIGHT MILD AGAIN AND MAINLY LOWER TO MID 60S. 

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 433 AM CDT SUN JUN 29 2014

925-850 HPA CONVERGENCE LINGERS THROUGH MOST OF MONDAY MORNING
ACROSS THE SOUTHEASTERN CWA...AND ADDITIONAL FORCING FOR LIFT FROM
STRONG LOBE ROTATING AROUND UNSEASONABLY STRONG UPPER LOW SHOULD
HELP TO ENHANCE ACTIVITY A BIT FOR THE FIRST FEW HOURS IN THE
MORNING BEFORE STRONGER PUSH ALOFT BEHIND MID LEVEL WAVE SHOVES
BOUNDARY SOUTHEAST AND OUT OF THE AREA. DECENT AMOUNT OF ELEVATED
CAPE SOUTHEAST OF A SPENCER IOWA TO CONCORD NEBRASKA LINE...WHERE
HIGH RESOLUTION SOLUTIONS INDICATE BEST POTENTIAL FOR DEVELOPMENT
THRU 18Z. AS SYSTEM PULLS OUT...STRONG GRADIENT ALOFT 25 TO 35
KNOTS WILL BE AVAILABLE TO MIX OUT ACROSS THE WESTERN/NORTHERN CWA
WITH GREATER SUNSHINE...AS TEMPS REACH FROM JUST SHY OF 80 IN THOSE
AREAS LONGEST TO CLEAR...TO SOME MID 80S WITH DECENT WESTERLY
MIXING COMPONENT.

TUESDAY CONTINUES TO LOOK A BIT MORE MORE DYNAMIC AS MAIN UPPER
LOBE SWINGS SOUTHWARD. WITH TEMPS ALOFT COOLING TO AROUND 2C AT
700 HPA AND SHARP CYCLONIC FLOW...WOULD EXPECT STRONG DIURNAL
ENHANCEMENT TO SHOWER COVERAGE PUSHING SOUTHEAST ACROSS THE CWA.
WILL PLAY UP DIURNAL TREND WITH MIDDAY THROUGH LATE AFTERNOON
MAX COVERAGE...THEN WINDING DOWN QUICKLY IN THE EVENING. SOME OF
THE WARMER TEMPS ARE EXPECTED AHEAD OF THE SHOWERY PRECIPITATION...
SO MAY ACTUALLY SEE HIGHS REACHED BY LATER MORNING/MIDDAY FOR SOME
AREAS...AND MORE OR LESS A LONG TERM OSCILLATION THROUGH THE
AFTERNOON WITH SCATTERED SHOWERS. DID ADD IN ISOLATED THUNDER EAST
AND SOUTH WITH EVEN THE LOWER END OF FORECASTED DEWPOINTS LIKELY
TO KEEP A FEW HUNDRED MLCAPE GOING IN THE AFTERNOON...WITH ENOUGH
CLOUD DEPTH TO GET SOME CHARGE SEPARATION INITIATED.

LAST UPPER ENERGY SWEEPS SOUTHWARD TO OUR EAST ON WEDNESDAY...WHICH
WILL HELP TO KEEP MORE CLOUDS IN THE MIX ALONG/EAST OF I29 ON
WEDNESDAY...ALONG WITH LOCKING IN COOLER AIR JUST A BIT LONGER.
HAVE NUDGED SOME HIGHS DOWN AGAIN...BUT WOULD THINK EVEN A FEW
MORE DEGREES TRIMMING MIGHT BE NECESSARY...ESPECIALLY EAST.

SOMEWHAT MORE CERTAIN THAT WARMER AIR WILL BE A BIT SLOWER TO
BUILD IN NEXT WEEKEND...BUT SHOULD BE A CONSISENT TREND TOWARD
WARMER AND MORE HUMID. LINGERING LOW LEVEL RIDGE TO THE EAST
SHOULD SLOW UP MEANINGFUL PRECIP THREAT WELL INTO FRIDAY NIGHT
WITH WEAK WAVE IN NW FLOW COLLOCATING WITH WARM AIR ADVECTION...
BUT PERHAPS A LITTLE ELEVATED ACTIVITY IN THE NORTH LATER THURSDAY
NIGHT...AND ACROSS THE NORTHEAST ON FRIDAY. MAIN CONVERGENCE ZONE
STILL TO THE NORTH/NORTHEAST...BUT CLOSE ENOUGH TO KEEP IN POPS.
DIRECTIONAL SHEAR WOULD BE APPRECIABLE SHOULD ANYTHING TRY TO
HEAD TOWARD NEAR SURFACE BASED...SO WOULD HAVE TO MONITOR FOR 
A SEVERE WEATHER POTENTIAL OVER THE HOLIDAY WEEKEND. GFS LOOKS TO
HAVE A LITTLE FEEDBACK WITH SPONTANEOUS UPPER LOW DEVELOPMENT...AND
HAVE SIDED MORE TOWARD A CANADIAN/ECMWF PROGRESSION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 603 AM CDT SUN JUN 29 2014

MAINLY VFR THROUGH THE PERIOD. THERE WILL BE A THREAT FOR
THUNDERSTORMS OVER ESPECIALLY NORTHWEST IOWA LATER THIS AFTERNOON
INTO THE OVERNIGHT HOURS. MOST OF EASTERN SOUTH DAKOTA INTO
SOUTHWEST MINNESOTA WILL REMAIN DRY WITH THE BEST CHANCES FOR
THUNDERSTORMS ACROSS IOWA AND NEBRASKA.

&&

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

$$

SHORT TERM...08
LONG TERM...CHAPMAN
AVIATION...08