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000
FXUS63 KFSD 161132
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
632 AM CDT SUN JUN 16 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 348 AM CDT SUN JUN 16 2013

PLUME OF MOISTURE AND 850MB THETAE RIDGING ADVECT INTO WESTERN AND
CENTRAL SD AS THE MORNING PROGRESSES...THEN EVENTUALLY AFFECT OUR
WESTERN ZONES BY LATE MORNING AND MIDDAY. MODERATE ML CAPE VALUES
FOLLOW SUIT IN ARCHING UP INTO CENTRAL SD FROM NEBRASKA THROUGH
MIDDAY...THEN INCREASE FOR POINTS EASTWARD THROUGH THE AFTERNOON
HEADING TOWARD I 29. THE DIFFERENCE BETWEEN TODAY AND YESTERDAY
MORNING HOWEVER...IS SATURDAY MORNING HAD A VERY DISTINCT SHORT WAVE
PASSAGE WITH THE CONVECTION. TODAY...MODEL CONSENSUS DEVELOPS THE
SHORT WAVE OVER THE WESTERN PLAINS THEN DIVE IT SOUTH OF OUR
FORECAST AREA IN THE AFTERNOON. IN ADDITION...CORFIDI VECTORS FOR
ORGANIZED CONVECTION ALSO ORIENTATE IN A NW TO SE DIRECTION.
THEREFORE BELIEVE THAT THE CONVECTION IN OUR FORECAST AREA WILL BE
PURELY DRIVEN BY THETAE ADVECTION AND INSTABILITY...GIVING IT MORE
OF A SCATTERED NATURE THEN NUMEROUS OR WIDESPREAD CATEGORICAL. THERE
IS ENOUGH INSTABILITY THAT SOME MARGINAL SEVERE IS A THREAT IN OUR
WESTERN ZONES THIS AFTERNOON. IN ADDITION...THERE IS DECENT WIND
SHEAR VEERING WITH HEIGHT HOWEVER SPEEDS ARE MARGINAL. CERTAINLY
WORTH MENTIONING THE POSSIBILITY IN THE FORTH COMING HWO.

CONCERNING TEMPERATURES TODAY...MANY CONSENSUS GUIDANCE VALUES HAVE
BEEN RUNNING A LITTLE BIT COOL LATELY. THEREFORE DECIDED TO BLEND
SOME OF THE WARMER GUIDANCE READINGS SUCH AS MOS WITH THE MET AND
MAV. 850MB TEMPERATURES STRONGLY SUGGEST THAT HIGHS SHOULD BE IN THE
80S...WITH MANY GUIDANCE VALUES IN THE UPPER 70S. THE ONLY WAY
TEMPERATURES WOULD BE HELD DOWN IN THE 70S IS IF THICK CLOUD COVER
DEVELOPED MORE THEN EXPECTED.

A FRONTAL BOUNDARY/WIND SHIFT LINE DROPS SOUTHWARD ACROSS THE AREA
TONIGHT...WITH WEAK LOW LEVEL CONVERGENCE ASSOCIATED WITH THE
FEATURE. KEPT SMALL CHANCE POPS FOR SCATTERED CONVECTION THROUGH THE
EVENING HOURS IN OUR NORTH AND WEST WITH AN 850 MB THETA
E/INSTABILITY AXIS ORIENTED ACROSS THAT AREA OUT AHEAD OF THE
FRONTAL BOUNDARY. ANY CONVECTION LOOKS TO BECOME MORE ISOLATED LATER
IN THE NIGHT WITH WEAKENING INSTABILITY AND THETA E ADVECTION...WITH
THE BOUNDARY FINALLY MAKING IT THROUGH THE CWA TOWARD 12Z ON MONDAY.
WITH RESULTANT LOW LEVEL COLD AIR ADVECTION BEHIND THE
FEATURE...COOLER OVERNIGHT READINGS WILL RESIDE IN THE NORTH...MID
50S...WHILE LOWER 60S LOOKS APPROPRIATE IN OUR FAR SOUTHEASTERN
ZONES.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 348 AM CDT SUN JUN 16 2013

SURFACE RIDGING BEGINS TO BUILD INTO THE REGION ON MONDAY. MODELS
INDICATE ANOTHER SHORTWAVE DROPPING THROUGH THE UPPER MIDWEST ON
MONDAY AFTERNOON IN A NORTHWESTERLY UPPER LEVEL FLOW...WITH THE GFS
BRINGING THIS ENERGY A LITTLE FARTHER TO THE SOUTH AND WEST THAN THE
OTHER MODELS...AND THUS BREAKING OUT CONVECTION IN OUR NORTHEAST
DURING THAT TIME FRAME. ELECTED TO LEAVE THIS MENTION OF
PRECIPITATION OUT OF THE FORECAST WITH IT BEING AN OUTLIER...BUT
WILL BE SOMETHING TO KEEP AN EYE ON. TEMPERATURES WILL BE SEASONABLY
PLEASANT ON MONDAY...IN THE MID 70S TO NEAR 80. WITH MOSTLY CLEAR
SKIES AND LIGHT WINDS ON MONDAY NIGHT WILL HAVE LOWS IN THE MID AND
UPPER 50S.

HIGH PRESSURE MOVES TO THE EAST ON TUESDAY...WITH A RETURNING
SOUTHERLY FLOW TO OUR AREA. BY TUESDAY AFTERNOON...INCREASING 850 MB
THETA E ADVECTION AND INSTABILITY WILL BEGIN TO CREEP BACK INTO
WESTERN AND CENTRAL SOUTH DAKOTA. IN THE ABSENCE OF ANY SHORTWAVE TO
SPEAK OF...NOT EXPECTING MUCH IN THE WAY OF CONVECTION IN OUR AREA
...THOUGH CANNOT RULE OUT ISOLATED THUNDERSTORM MAKING IT INTO OUR
FAR SOUTHWEST ON TUESDAY AFTERNOON OR EVENING WITH CONVECTION WHICH
MAY DEVELOP TO OUR WEST WHERE DYNAMICS ARE SLIGHTLY BETTER. WILL
BEGIN TO SEE SUBTLE WARMING ON TUESDAY WITH HIGHS INTO THE UPPER 70S
TO LOWER 80S.

FOR WEDNESDAY INTO SATURDAY...UPPER LEVEL RIDGING BUILDS INTO THE
CENTRAL PART OF THE NATION. THIS WILL PLAY OUT TO A BIT OF WARMING
EACH DAY WITH HIGHS INTO THE MID AND UPPER 80S BY SATURDAY. MODELS
ARE ALL OVER THE PLACE WITH RESPECT TO SHORTWAVES EMBEDDED IN THE
UPPER LEVEL FLOW...SO STAYED CLOSE TO CONSENSUS GUIDANCE WITH REGARD
TO CONVECTION CHANCES THROUGH THE PERIOD...WITH THE BETTER CHANCES
IN THE THURSDAY AND FRIDAY NIGHT TIMEFRAME.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 632 AM CDT SUN JUN 16 2013

AREAS OF MVFR TO IFR VISIBILITIES WILL BE PREVALENT IN NORTHWEST
IA UNTIL ABOUT 14Z THIS MORNING...OTHERWISE TODAY WILL BE VFR.
ANOTHER SHORT WAVE OF ENERGY WILL BE MOVING FROM NORTHWEST TO
SOUTHEAST TODAY. IT APPEARS MUCH OF THE STRONGEST PART OF THE WAVE
WILL MOVE INTO NEBRASKA. BUT WITH CONVECTION ALREADY FIRING IN
WESTERN NEBRASKA AND SOUTHWEST SD AS EXPECTED...CANNOT RULE OUT A
FEW TSRA AT THE KHON AND KSUX TAF SITES THIS AFTERNOON. AT THIS
TIME...DO NOT HAVE ENOUGH CONFIDENCE TO INCLUDE THUNDERSTORMS IN
THE KFSD TAF FOR THIS AFTERNOON. THE THUNDERSTORMS WILL LIKELY
USHER FAIRLY RAPIDLY SOUTHEASTWARD LATE THIS AFTERNOON...THEREFORE
LEFT THE TAF SITES DRY FOR THIS EVENING. A WEAK COLD FRONT WILL
MOVE THROUGH OUR SOUTH DAKOTA ZONES LATE TONIGHT AFTER MIDNIGHT...
SHIFTING THE WINDS TO THE NORTH. AHEAD OF THE FRONT...WOULD NOT BE
SURPRISED TO SEE SOME MORE AREAS OF MVFR TO IFR FOG IN NORTHWEST
IA IN THE PRE DAWN HOURS OF MONDAY.

&&

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

$$

SHORT TERM...MJF/JM
LONG TERM...JM
AVIATION...MJF