Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 252307
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
607 PM CDT FRI JUL 25 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 323 PM CDT FRI JUL 25 2014

STRATO-CU FIELD CONTINUES TO FILL IN AND DRIFT SOUTH AHEAD OF AN
APPROACHING FRONTAL BOUNDARY.  THIS BOUNDARY CONTINUES TO SLOWLY
WASHOUT AS IT MOVES THROUGH THE CWA...WITH DRIER BOUNDARY LAYER AIR
FAILING TO ADVECT INTO THE AREA. INCREASED CLOUDS...BOUNDARY LAYER
MOISTURE...AND LIGHT WINDS ARE HAMPERING AFTERNOON MIXING/HEATING
AND TEMPERATURES MAY FALL A FEW DEGREES SHORT OF EXPECTATIONS BY
LATE AFTERNOON.

TONIGHT...MID-UPPER LEVEL JET STREAK WILL EJECT INTO THE PLAINS AS
INFLUENCE OF SOUTHERN ALBERTA TROUGH BECOME MORE PRONOUNCED.  SUBTLE
SHORTWAVE ENERGY CROSSING THE DAKOTAS WILL INDUCE A BRIEF PERIOD OF
RETURN FLOW AND MODEST MID-LEVEL THETA-E ADVECTION TOWARDS MIDNIGHT.
MODELS STILL SHOWING STRONG SIGNALS FOR THE DEVELOPMENT OF HIGH
BASED ELEVATED CONVECTION ACROSS SOUTH CENTRAL SD AFTER
MIDNIGHT...MUCAPE PLOTS SUGGEST 2000 J/KG AVAILABLE...BUT DOUBTFUL
GIVEN ELEVATED LIFTING LEVEL THAT MUCH OF THIS WOULD BE REALIZED.
STILL...COULD NOT RULE OUT SMALL HAIL IN STORMS ESPECIALLY ALONG AND
WEST OF THE MISSOURI RIVER VALLEY.  WITH MOISTURE HANGING AROUND AND
LIGHT WINDS...MAY HAVE TO WATCH FOR A BRIEF PERIOD OF LIGHT FOG
TOWARD DAYBREAK.  PROBABILITY PLOTS CONTINUE TO POINT TO A NIL
EVENT...SO HAVE LEFT OUT FOR NOW.

SATURDAY...MORNING CONVECTION WILL SLIDE SOUTH SOUTHEAST IN THE
MORNING...AS MORE STABLE AIR ADVECTS SOUTHEAST.  TEMPERATURES AGAIN
WILL BE TRICKY WITH MODELS PLACING A FAIRLY SUBSTANTIAL MID-LVL DECK
OVER THE CWA THROUGH MID-DAY AND QUESTIONS ABOUT HOW LONG
PRECIPITATION COULD LINGER IN THE MORNING.  WINDS WILL AGAIN REMAIN
LIGHT...PROHIBITING DEEP MIXING AND THUS WILL KEEP WITH A NEAR
NORMAL TEMPERATURE FORECAST.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 323 PM CDT FRI JUL 25 2014

OVERALL PATTERN IN THE EXTENDED PD IS HIGH OVER THE SOUTHERN/SW US
WITH RIDGING AND WELL ABOVE NORMAL TEMPS OVER THE WEST COAST AND AND
H5 LOW NEAR THE US/CANADA BORDER THAT WILL DIVE SOUTHEAST AND BRING
ANOTHER ROUND OF BELOW NORMAL TEMPS FROM THE PLAINS TO THE EAST
COAST.

BOTH THE GFS/ECMWF ARE SIMILAR ENOUGH WITH LARGER SCALE DETAILS THAT
A BLEND OF THE TWO WILL BE SUFFICIENT. AFOREMENTIONED H5 LOW IS
FORECAST TO BE NEAR THE WESTERN GREAT LAKES BY SUNDAY AND BY MONDAY
IS EAST OF THE GREAT LAKES AND IS ABSORBED INTO THE LARGER LOW THAT
HAS BEEN HANGING OVER EASTERN CANADA. AS THIS LOW MOVES THROUGH THE
NORTHERN PLAINS FLOW ALOFT TURNS NORTHWEST AND COOLER AIR SETTLES
IN.  THIS PATTERN REMAINS FAIRLY STEADY THROUGH MID WEEK NEXT WEEK
WHICH WILL RESULT IN TEMPS NOT EVEN GETTING OUT OF THE 70S UNTIL
LATE NEXT WEEK.  TOWARD THE END OF THE EXTENDED PD TEMPS START
SLOWLY WARMING INTO THE LOW 80S BUT WILL STILL BE BELOW NORMAL.

AS FAR AS PRECIP GOES...NO BIG PRECIP EVENTS ARE EXPECTED AT THIS
TIME.  THERE COULD BE SOME ISOLATED SHOWERS AT TIMES LATE NEXT WEEK
BUT CHANCES ARE VERY LOW AND HAVE NOT INCLUDED POPS AT THIS TIME.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 602 PM CDT FRI JUL 25 2014

LIGTH AND VARIABLE WINDS OVERNIGHT. THERE WILL BE A CHANCE OF
THUNDERSTORMS THROUGH THE MISSOURI RIVER CORRIDOR AFTER 09Z...WITH
LINGERING CHANCES THROUGH MID MORNING ON SATURDAY. CONFIDENCE TOO
LOW TO INCLUDE IN TAFS.

&&

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

$$

SHORT TERM...DUX
LONG TERM...SALLY
AVIATION...JM





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