205 
FXUS63 KFSD 220256
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD...CORRECTION
955 PM CDT THU JUN 21 2012

.DISCUSSION.../ISSUED AT 826 PM CDT/
LITTLE CHANGE TO PREVIOUS FORECAST. WITH DEW POINTS AROUND 
50...WINDS GOING LIGHT FAIRLY QUICKLY AFTER SUNSET AND CLEAR SKIES 
FOR A FEW HOURS...HAVE LOWERED MINS A COUPLE OF DEGREE EAST OF THE 
JAMES RIVER. OTHERWISE...STILL LOOKS LIKE THERE WILL BE ISOLATED 
SHOWERS AND THUNDERSTORMS LATE TONIGHT AND TOMORROW MORNING ALONG 
AND NORTH OF I-90 AS PARCELS LIFTED FROM AROUND 700 MB HAVE CAPES OF 
100-300 J/KG.

UPDATED ZFP...PFM...AND GRIDS AVAILABLE./SCHUMACHER

&&

.AVIATION.../FOR 00Z TAFS/
VFR CONDITIONS EXPECTED THROUGH THE FORECAST PERIOD. LIGHT AND 
VARIABLE WINDS OVERNIGHT...WILL PICK UP OUT OF THE SOUTHEAST AFTER 
14Z ON FRIDAY BECOMING SUSTAINED AROUND 12KTS IN THE LATE AFTERNOON. 
THERE WILL BE A POSSIBILITY OF ISOLATED THUNDERSTORMS DEVELOPING 
OVER CENTRAL SOUTH DAKOTA LATE TONIGHT...THEN TRACKING TO THE 
EAST...GENERALLY NORTH OF INTERSTATE 90...INTO THE MID MORNING HOURS 
OF FRIDAY BEFORE DISSIPATING. IF STORMS DEVELOP...THEY WILL BE VERY 
ISOLATED IN NATURE AND THUS DID NOT INCLUDE IN THE KHON OR KFSD TAFS.

&& 

.PREV DISCUSSION.../ISSUED AT 320 PM CDT/
THE FAIR WEATHER CUMULUS ACROSS THE NORTHERN PART OF THE CWA WILL 
DISSIPATE AS THE SUNS SETS THIS EVENING AND HIGH PRESSURE BUILDS IN. 
WITH CLEAR SKIES AND LIGHT WINDS...SHOULD SEE LOWS DROP INTO THE 
50S. WILL SEE A MID LEVEL FRONT AND ASSOCIATED STRONG THETAE 
ADVECTION APPROACH AFTER MIDNIGHT TONIGHT. THIS WILL BRING AN 
INCREASE IN MID LEVEL CLOUDS FROM WEST TO EAST BEGINNING AFTER 
MIDNIGHT. ALSO LOOKS LIKE WE SHOULD SEE A THIN LAYER OF 
INSTABILITY...MAINLY BETWEEN 700-500 MB WITH THIS FEATURE. THIS MAY 
BE ENOUGH TO GET A FEW ELEVATED SHOWERS...AND MAYBE AN ISOLATED 
THUNDERSTORM TO FORM LATE TONIGHT INTO TOMORROW MORNING. ALTHOUGH 
THE ATMOSPHERE IS RATHER DRY BELOW 700MB WHICH MAY PREVENT ANY RAIN 
FROM REACHING THE SURFACE. DECIDED TO LEAVE THE ISOLATED POPS IN THE 
GRIDS...MANLY FROM INTERSTATE 90 AND NORTH...JUST MOVED THE TIMING 
UP A BIT. ANY SHOWERS THAT DO FORM WILL HAVE PUSHED EAST OF 
INTERSTATE 29 BY NOON...AND OUT OF THE CWA SHORTLY AFTER. HIGHS IN 
SOUTHWEST MINNESOTA MAY BE HELD DOWN A BIT FROM THE CLOUDS...BUT 
ELSEWHERE WE SHOULD SEE THEM CLEAR IN TIME FOR GOOD HEATING. WENT 
CLOSER TO THE WARMER GUIDANCE FOR HIGHS...RANGING FROM AROUND 80 IN 
SOUTHWEST MINNESOTA TO AROUND 90 WEST OF THE JAMES RIVER. WINDS WILL 
TURN SOUTH SOUTHEASTERLY ON FRIDAY...AND BECOME GUSTY WEST OF THE 
JAMES RIVER...WITH GUSTS AROUND 30 MPH. /CHENARD

BY FRIDAY NIGHT...A MID LEVEL SHORTWAVE EJECTS FROM THE CENTRAL 
ROCKIES AND IS EXPECTED TO MOVE THROUGH THE RIDGE OVERNIGHT AND INTO 
EARLY SATURDAY. COULD SEE AN INITIAL WAVE OF SCATTERED ELEVATED 
THUNDERSTORMS FIRE ACROSS THE BLACK HILLS AREA AND WESTERN NEBRASKA 
LATE AFTERNOON ON FRIDAY WHILE THE LOW LEVEL JET PICKS UP AND STARTS 
TAPPING INTO BETTER MOISTURE. THESE STORMS MAY WORK THEIR WAY INTO 
OUR WESTERN BORDER BY LATE EVENING INTO THE EARLY OVERNIGHT HOURS.  
AS THE SHORTWAVE APPROACHES AFTER MIDNIGHT...STORMS WILL BECOME MORE 
LIKELY OVERNIGHT. STILL SEEING QUITE A BIT OF DIFFERENCE IN THE WAY 
MODELS ARE HANDLING THIS WAVE...WITH THE LATEST RUN OF THE NAM 
FOCUSING THE WAVE OVER THE MISSOURI VALLEY AND INTERSTATE 90...THE 
ECMWF ACROSS THE INTERSTATE 90 CORRIDOR AND THE GFS SPLITTING THE 
ENERGY WELL NORTH AND SOUTH OF THE FORECAST AREA. WILL CONTINUE TO 
FOCUS THE BEST POTENTIAL FOR STORMS ACROSS THE MISSOURI VALLEY WITH 
CONCERN THAT MOISTURE MAY HAVE DIFFICULTY BUILDING NORTHWARD IF 
CONVECTION MANAGES TO FIRE ACROSS NEBRASKA ON FRIDAY EVENING. 

SHORTWAVE KICKS OUT OF THE AREA SATURDAY AFTERNOON AS THE UPPER 
LEVEL RIDGE BUILDS BACK INTO THE HIGH PLAINS. THE RIDGING BECOMES 
MORE AMPLIFIED AND EXPANDS A BIT EASTWARD INTO THE FIRST HALF OF THE 
WEEK. EXPECT MAINLY DRY WEATHER DURING THIS PERIOD WITH MOSTLY CLEAR 
TO PARTLY CLOUDY SKIES. COULD SEE A FEW WEAK IMPULSES EJECT FROM THE 
DEEP TROUGH OVER THE INTERMOUNTAIN WEST AND TRY TO TOP THE SHARP 
RIDGE. COULD SEE SOME VERY MINOR POPS CREEP INTO OUR FAR WESTERN CWA 
MONDAY EVENING THROUGH TUESDAY...BUT WITHOUT MUCH MOISTURE TRANSPORT 
AND WITH MODELS NOT ENTIRELY IN AGREEMENT...WILL LEAVE OUT MENTION 
OF POPS FOR NOW. GFS REMAINS MORE AGGRESSIVE WITH BREAKING DOWN THE 
RIDGE TOWARDS MID WEEK WHILE INTRODUCING A DECENT POTENTIAL FOR 
PRECIPITATION. HOWEVER...THIS SOLUTION CONTINUES TO BE SOMEWHAT OF 
AN OUTLIER COMPARED TO THE ECMWF AND ENSEMBLES. TEMPERATURES LOOK TO 
REMAIN NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD WITH WINDS 
GENERALLY EAST TO SOUTHEAST PREVENTING THINGS FROM BECOMING TOO MIXY.

&&

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

&&

$$