000
FXUS63 KFSD 221723
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1223 PM CDT WED MAY 22 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CDT WED MAY 22 2013

UPPER LEVEL LOW CONTINUES TO SPIN ACROSS THE AREA EARLY THIS
MORNING...FAIRLY CLOSE TO KYKN...BUT WITH SOME UNCERTAINTY GIVEN
WHAT IS HOPEFULLY A TEMPORARY LOSS OF THE GOES-EAST DATA DUE TO
LATE EVENING MALFUNCTION /ESTIMATED RETURN TOWARD 18Z TODAY/.
BULK OF PRECIPITATION CONTINUING TO OCCUR JUST ON BACK SIDE OF THE
MID LEVEL CENTER WHERE TENDENCY TO FOCUS A BIT OF LOWER TO MID LEVEL
FRONTOGENESIS AND ISENTROPIC LIFT IN THE 295-300K LAYER. RETURNS
HAVE REALLY VARIED OVERNIGHT...SOMETIMES NEARLY DISSIPATING...ONLY
TO REFORM AND BECOME QUITE WIDESPREAD JUST AN HOUR LATER. AT CURRENT
TIME...ABOUT THE BEST COVERAGE OF THE NIGHT SO FAR ALONG AND WEST OF
I29 AS PULSE IN THE ISENTROPIC LIFT WORKS WESTWARD NORTH OF THE
CYCLONE CENTER. TREATING LIKE A CLASSIC HIGH POP/LOW QPF EVENT AT
LEAST THROUGH THE EARLY MORNING HOURS...WITH SIGNS IN SEVERAL MODELS
OF A WEAKENING OF THIS TROWAL-LIKE FEATURE THROUGH THE MORNING...
BUT PERHAPS A RESURGENCE IN COVERAGE BY EARLY TO MID AFTERNOON NEAR
AND JUST E OF I29 IF SOLUTIONS TAKEN LITERALLY. GENERALLY...EXPECT A
DAY WITH OCCASIONAL SHOWERS...STARTING TO DWINDLE FROM THE WEST. NOT
EXPECTING TO SEE MUCH IN THE WAY OF CLEARING TODAY...PERHAPS A
PARTIAL BIT LEAKING INTO THE FAR NORTH/NORTHWEST. THUS WITH CLOUDS
AND EXPECTED PRECIPITATION...ANOTHER CHILLY DAY WITH FAIRLY LIMITED
RECOVERY FROM CURRENT READINGS...MEANING HIGHS 10 TO 15 DEGREES
BELOW NORMAL.

PRECIPITATION SHOULD WIND DOWN THROUGH THE EVENING HOURS TONIGHT
AS ISENTROPIC DOWN GLIDE INCREASES ACROSS THE AREA. ADDED MENTION
OF PATCHY FOG ACROSS CENTRAL SOUTH DAKOTA WHERE SKIES CLEAR AND
WINDS DECREASE. CONSIDERED EXPANDING FURTHER EAST...BUT FOG IS
CONDITIONAL ON TIMING OF CLEARING AND WIND POTENTIAL.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 340 AM CDT WED MAY 22 2013

RELATIVELY QUIET WEATHER IS EXPECTED ON THURSDAY WITH SURFACE
RIDGE PASSING THROUGH THE REGION TO THE NORTH. MODELS SUGGEST
RETURN FLOW SETS UP FAIRLY QUICKLY THURSDAY AFTERNOON INTO
THURSDAY NIGHT...THOUGH NO DIRECT TAP TO THE GULF IS PRESENT SO AM
NOT EXPECTING A SUBSTANTIAL INCREASE IN MOISTURE UNTIL FRIDAY NIGHT
INTO SATURDAY WHEN LOW LEVEL JET SETS UP ACROSS THE CENTRAL
PLAINS. MODELS SEEM TO SUGGEST A FAIRLY WEAK CAPPING
INVERSION...WITH THE POTENTIAL FOR STORMS TO DEVELOP AS A LEADING
SHORT WAVE BREAKS OFF UPPER LOW SPINNING ACROSS THE NW US. THE
ECMWF SUGGESTS THE UPPER WAVE MAY SHEAR OUT TO THE NORTH AND WEST
OF THE CWA AS IT TRIES TO WORK EAST INTO THE UPPER RIDGE ACROSS
THE CENTRAL PLAINS...WHILE THE GFS SUGGESTS A SERIES OF PHASED
WAVES TRAVELING ACROSS THE AREA. THE WAVES IN THE GFS SOLUTION
APPEAR TO BE CONVECTIVE DRIVEN...AND HAVE THEREFORE SIDED CLOSER
TO AN ECMWF SOLUTION. WITH THAT SAID...WAS NOT THAT EXCITED ABOUT
PRECIPITATION CHANCES AND LOWERED POPS SLIGHTLY...ESPECIALLY
DURING THE DAY ON FRIDAY. WITH BETTER MOISTURE RETURN FRIDAY
NIGHT...PRECIPITATION CHANCES APPEAR TO BE MORE SIGNIFICANT WITH
LITTLE CAPPING INVERSION FROM A LIFTING LAYER BETWEEN 700-800 MB.

OFF AND ON CHANCES OF PRECIPITATION CONTINUE TO PLAGUE THE
EXTENDED WITH DIRTY WEST TO SOUTHWEST FLOW ALOFT WITH WAVES
BREAKING OFF IN A PIECEMEAL FASHION AND MOVING THROUGH THE PLAINS.
WITH UPPER LOW REMAINING TO THE WEST...LOW LEVEL FLOW REMAINS
SOUTHEAST TO SOUTH THROUGH MUCH OF THE EXTENDED. THIS WILL RESULT
IN AN OVERALL GRADUAL WARMING TREND...ALONG WITH AN INCREASE IN
MOISTURE. WITH LITTLE AGREEMENT ON TIMING OF UPPER WAVES...LEFT
GUIDANCE POPS AS IS WITH CHANCES OF THUNDERSTORMS THROUGHOUT THE
EXTENDED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1223 PM CDT WED MAY 22 2013

WIDESPREAD MVFR CIGS THIS EARLY AFTERNOON ALONG WITH SCT TO
NUMEROUS SHOWERS WILL CONTINUE THROUGH LATE AFTERNOON. SHOWERS
WILL DIMINISH FROM WEST TO EAST THIS EVENING TONIGHT ALTHOUGH LOW
LEVEL MOISTURE WILL REMAIN IN PLACE. IFR CIGS ARE EXPECTED
TO REDEVELOP WITH DECOUPLING LATER THIS EVENING AT SUX/FSD.
CLEARING IS EXPECTED TO PUSH IN FROM THE NORTH OVERNIGHT FIRST AT
HON AND THEN FSD...HOWEVER RESIDUAL MOISTURE WILL LIKELY RESULT IN
SOME AREAS OF RADIATIONAL BR/FG...ESPECIALLY IN HON VICINITY.
CLEARING OF LOW LEVEL STRATUS MAY ALSO OCCUR SLOWER THAN FORECAST
BY A FEW HOURS DUE TO VEERING WINDS IN A MOISTURE FAVORED ENE
DIRECTION. HOWEVER...BEFORE THE END OF THE TAF
PERIOD...HON/FSD/SUX SITES SHOULD ALL BE VFR.

&&

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

$$

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