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000
FXUS63 KFSD 301753
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1253 PM CDT WED JUL 30 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 413 AM CDT WED JUL 30 2014

ANOTHER UNSEASONABLY COOL BUT PLEASANT DAY ON TAP FOR THE REGION
WITH WEAK NORTHWEST UPPER FLOW LOCKED INTO NORTHERN AND CENTRAL
PLAINS. SOME MINOR THETA E ADVECTION SETS UP ACROSS CENTRAL SOUTH
DAKOTA AND NOSES TOWARDS OUR WESTERN BOUNDARY THIS AFTERNOON. EXPECT
THE MAIN IMPACT OF THIS FEATURE TO BE AN INCREASE IN MID AND HIGH
CLOUDS MAINLY ALONG AND EAST OF THE JAMES RIVER. TO THE EAST...SKIES
WILL BE MOSTLY SUNNY SOME WIDELY SCATTERED DIURNAL CUMULUS POPPING
UP BY AFTERNOON. WITH A SLIGHT BOOST IN MID LEVEL TEMPERATURES AND
DECENT MIXING UNDER MOSTLY SUNNY SKIES...TEMPERATURES SHOULD BE A
FEW DEGREES WARMER THAN YESTERDAY WITH HIGHS IN THE UPPER 70S AND
LOWER 80S.

LIGHT AND VARIABLE WINDS TONIGHT...CLEARING SKIES AND THE PERSISTENT
COOL AIRMASS WILL ALLOW FOR ANOTHER CHILLY NIGHT. FOLLOWING RECENT
FORECAST TRENDS...DID NUDGE TOWARDS THE COOLER END OF GUIDANCE FOR
LOWS. THE EXCEPTION WILL BE ACROSS SOUTH CENTRAL SD WHERE THE
THERMAL BOUNDARY AND MID LEVEL CLOUDS PERSIST OVERNIGHT. A VERY
SUBTLE MID LEVEL WAVE DROPS SOUTHWARD AND CLIPS THIS AREA LATE
TONIGHT...SO WILL LEAVE VERY LOW END POPS IN PLACE - ISOLATED SHOWER
MENTION. QPF WILL BE VERY LIGHT WITHOUT MUCH MOISTURE TO WORK WITH
AND DRY LOW LEVELS...AND MAY BE MORE AKIN TO SPRINKLES THAN SHOWERS.
LOWS TONIGHT FALL INTO THE LOW 50S TO NEAR 60.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 413 AM CDT WED JUL 30 2014

NOISY NORTHERLY FLOW INTO THE START OF THE WEEKEND DOES POSE THE
POSSIBILITY OF GETTING A FEW HARD TO RESOLVE PERIODS OF
CONVECTION. WAVE SLIDING DOWN ON THURSDAY THROUGH THE EASTERN
PLAINS HAS GAINED QUITE A BIT OF CONSISTENCY OVER THE LAST SEVERAL
RUNS. WATER VAPOR LOOP VERIFIES LOCATION AND STRENGTH OF
WAVE...AND SEVERAL OTHER SUBTLE UPSTREAM IMPULSES SET TO CROSS
RIDGE AND DIVE INTO THE NORTHERN PLAINS.

BEST THERMODYNAMICS IN TERMS OF THETA E ADVECTION SEEM TO FOCUS
THROUGH THE WESTERN CWA EARLY IN THE DAY THURSDAY...BUT EVENTUALLY
AS SOME COOLER MID LEVEL AIR WORKS SOUTHWARD...AND WEAK AND ILL
DEFINED LOW LEVEL CONVERGENCE BOUNDARY SINKS SOUTHWARD...POSSIBLE
TO FIND AT LEAST A FEW SHOWERS OR THUNDERSTORMS DURING THE PEAK
DIURNAL HEATING CYCLE ACROSS MOST OF THE AREA. FAR FROM A
WASHOUT...AND MOST LIKELY TO REMAIN DRY.

ON FRIDAY...ANOTHER WAVE INDICATED...MORE FORMIDABLE IN THE NAM
AND SREF THAN OTHER SOLUTIONS. COULD EASILY ARGUE THAT WITH THE
WEAK LOW LEVEL FLOW...BOUNDARIES FROM ANY EARLIER CONVECTION
DURING THIS DIURNAL CYCLE MAY FOCUS A LITTLE DEVELOPMENT ACROSS
THE CWA WITH DISTINCT MID LEVEL THERMAL BOUNDARY IN PLACE...BUT
START TO SEE WARMING ALOFT WITH BUILDING HEIGHTS...AND EXPECT
A SOLUTION TOWARD MORE OF A CAP DEVELOPING...AND WILL NOT ADD
IN ANY ADDITIONAL PRECIP CHANCE FOR THIS PERIOD AT THIS TIME
WITH TEMPS PROBABLY NUDGING JUST A TOUCH WARMER THAN THURSDAY.

WEEKEND SHOULD BE DRY WITH WEAKENING RIDGE SHIFTING TOWARD THE
NORTHERN PLAINS...ALLOWING A SOUTH TO SOUTHWEST FLOW TO DEVELOP
WITH FALLING PRESSURE NORTH AND WEST. WARMEST OF THE AIRMASS WILL
POSITION WEST OF THE CWA ON SUNDAY...BUT THIS WILL BE THE MOST
LIKELY DAY OF HAVING TEMPS AT OR ABOVE NORMAL...BUT SATURDAY NOT
TOO FAR BEHIND.

THE PROSPECT FOR PRECIPITATION LOOKS TO FINALLY IMPROVE AT THE
START OF NEXT WEEK...AS RIDGE BREAKS DOWN WITH WAVE PUSHING INTO
THE PLAINS AROUND TUESDAY. SHOULD BE LED INTO BY A PERIOD OF
INCREASING LOW LEVEL MOISTURE/DEW POINT...AND POTENTIAL FOR
SLIGHTLY ABOVE NORMAL TEMPS SOUTH OF INCREASINGLY FRONTOGENETIC
BOUNDARY. COULD EVEN START TO CONSIDER AT LEAST A SMALL HEAVY RAIN
AND SEVERE WEATHER THREAT WITH INCREASING DIRECTIONAL SHEAR AND
INSTABILITY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1250 PM CDT WED JUL 30 2014

VFR CONDITIONS EXPECTED THROUGH THE PERIOD. A WEAK LOW PRESSURE
SYSTEM DROPPING SOUTH SHOULD BRING AN INCREASE IN MID LEVEL
CLOUDINESS SOMETIME LATER TONIGHT INTO TOMORROW. COULD ALSO SEE AN
ISOLATED SHOWER OR THUNDERSTORM...BUT PROBABILITY TOO LOW TO INCLUDE
IN TAFS AT THIS TIME.

&&

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

$$

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