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000
FXUS63 KFSD 170833
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
333 AM CDT MON JUN 17 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 332 AM CDT MON JUN 17 2013

SCATTERED THUNDERSTORMS HAVE ONCE AGAIN DEVELOPED ACROSS SOUTHWEST
SD AND WEST CENTRAL WY AT THIS TIME. THIS CONVECTION IS AT THE
LEADING EDGE OF ANOTHER WEAK SHORT WAVE WHICH WILL MOVE SOUTHEAST
THROUGH THE DAY. A STRIPE OF MODERATELY HIGH ML CAPES OF ABOUT
1000 TO 2000 J/KG EXTEND FROM THAT AREA...SOUTHEASTWARD ALONG THE
NEB/SD BORDER AND INTO NEB FOR TODAY. MEAN FLOW AND CORFIDI
VECTORS STRONGLY SUGGEST THAT THE CONVECTION WILL DRIFT TO THE
EAST/SOUTHEAST TO SOUTHEAST THIS MORNING. THEREFORE INCLUDED SOME
SMALL POPS FOR GREGORY COUNTY AS THE ANTICIPATED TRAJECTORY OF THE
RAIN COULD SCRAPE OUR FAR SOUTHWEST. BY AFTERNOON...RAINFALL
CHANCES SHOULD SHIFT FURTHER SOUTHWARD.

LATE THIS AFTERNOON AND EVENING...YET ANOTHER SHORT WAVE MOVES
DOWN THE NW FLOW ALOFT. CURRENT THOUGHTS ARE THAT THIS WAVE WILL
HAVE MINIMAL IMPACT ON OUR FORECAST AREA AS HUMIDITY TIME SECTIONS
AND VARIOUS MODEL SOUNDINGS INDICATE QUITE A BIT OF DRY AIR TO
OVERCOME...NOTING THAT THE LOW TO MID LEVEL FLOW IS ALSO OUT OF
THE NORTHWEST. CONCERNING TEMPERATURES...AFTER SEEING THIS PAST
WEEKENDS HIGHS...AND ALSO QUITE A BIT OF DENSE CLOUD COVER ON
SUNDAY AT LEAST OVER THE SOUTHERN HALF OF OUR AREA...MANY MODEL
CONSENSUS GUIDANCE VALUES ARE RUNNING TOO COOL. THIS IS
ESPECIALLY TRUE WITH THE BIAS CORRECTED VALUES AS OF LATE. WITH
PROJECTED 850MB TEMPERATURES AND A DRIER NW FLOW TODAY...SEE NO
REASON NOT TO GO CLOSEST WITH THE WARM GUIDANCE READINGS OF THE
MOS...MAV AND MET. CONVERSELY TONIGHT WITH LIGHT WINDS...SOME OF
THE COOLER VALUES LOOKED GOOD AND WE MAY NOT BE QUITE COOL ENOUGH
IN MANY OF THE LOWER LOCATIONS.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 332 AM CDT MON JUN 17 2013

WITH THE AFOREMENTIONED SHORT WAVE MENTIONED ABOVE EAST OF OUR
AREA BY TUESDAY...TUESDAY LOOKS TO BE A PLEASANT SUMMER DAY WITH
FAIRLY LIGHT WINDS AND HIGHS IN THE UPPER 70S TO MID 80S. A
SURFACE RIDGE BEGINS TO MOVE EASTWARD...BRINGING WINDS AROUND TO A
SOUTHEAST DIRECTION FOR AREAS WEST OF I 29. THE SOUTHEAST SURFACE
FLOW WILL THEN ENCOMPASS OUR ENTIRE FORECAST AREA BY TUESDAY
NIGHT...GIVING WARMER LOWS WHEN COMPARED WITH TONIGHT.

THE NEXT SHORT WAVE WILL DEVELOP OFF OF THE CENTRAL ROCKIES LATE
TUESDAY...AND EDGE EASTWARD TOWARD CENTRAL SD BY 12Z WED. AS THE
LOW LEVEL JET INCREASES WEST OF OUR FORECAST AREA...WOULD NOT BE
SURPRISED TO SEE ELEVATED ISOLATED TO SCATTERED CONVECTION FIRE UP
TUESDAY EVENING...THEN MOVE INTO OUR FAR WESTERN ZONES AFTER
MIDNIGHT. AS THE SHORT WAVE MOVES EASTWARD ACROSS OUR FORECAST
AREA ON WEDNESDAY...ISOLATED TO SCATTERED CONVECTION WILL LIKELY
BE AROUND THROUGH THE DAY. THERE IS PLENTY OF MID LEVEL MOISTURE
SUGGESTING ELEVATED ACTIVITY. BUT SINCE IT IS ELEVATED...RIGHT NOW
CHANCES FOR RAIN AT ANY SINGLE GIVEN LOCATION ARE NOT REAL HIGH.
THEREFORE ONLY SKITTISH POPS ARE CURRENTLY WARRANTED FOR NOW. BUT
THAT SAID...THERE WILL LIKELY BE CONVECTION DOTTING THE AREA
THROUGH THE DAY. MAY EVENTUALLY JUST HAVE TO GO SCATTERED
THUNDERSTORMS GENERALLY IN THE 30 TO 40 PERCENT RANGE FORECAST
AREA WIDE IF THE MODEL TREND CONTINUES TO SHOW THIS IN FUTURE
FORECASTS. CONCERNING WEDNESDAY HIGHS...ONCE AGAIN THE BIAS
CORRECTED GUIDANCE VALUES LOOKED WAY TOO COOL...ESPECIALLY GIVEN
THE STRENGTHENING SOUTHERLY FLOW.

MORE WAVY ACTION APPEARS TO BE PREVALENT WEDNESDAY NIGHT IN OUR
AREA AHEAD OF A DEEPENING UPPER LOW OVER THE WESTERN U.S.. WITH A
STOUT LOW LEVEL JET CONTINUING...LINGERING CHANCES FOR
THUNDERSTORMS ARE WARRANTED. THE NAM12 SHOWS QUITE A STRONG
ELEVATED CIN GRADIENT ACROSS OUR FORECAST AREA SUGGESTING THAT
ELEVATED THUNDERSTORMS COULD ERUPT ON THE EDGE OF CAPPING. THIS IS
ESPECIALLY TRUE IN THE 850MB TO 750MB LAYER.

THE THURSDAY THROUGH SUNDAY PERIOD DEALS WITH THE PASSAGE OF THE
UPPER RIDGE TO JUST EAST OF OUR AREA AND THE GRADUAL APPROACH OF
A WESTERN U.S. TROUGH. THIS WILL BRING WARM AND INCREASINGLY
HUMID WEATHER TO THE NORTHERN PLAINS. AT THIS TIME THERE APPEARS
TO BE A THREAT OF SHOWERS AND THUNDERSTORMS EACH DAY AS HIGH
PLAINS SURFACE LOW SLOWLY MOVES INTO THE AREA AND FAIRLY DECENT
INSTABILITY PREVAILS. WILL NOT GET DIURNALLY SPECIFIC...THAT IS
EMPHASIZE NIGHTTIME ACTIVITY...WITH AS MUCH DEPENDENCE AS THERE
APPEARS TO BE ON UPPER DYNAMICS. THE LIKELIHOOD OF DRYING OVER THE
AREA APPEARS TO BE DELAYED UNTIL AFTER THE WEEKEND DUE TO THE SLOW
PROGRESSION OF THE TROUGH OVER THE UPPER RIDGE. THE ECMWF APPEARS
TO BE A BIT FASTER THAN THE GFS ON ALL THIS BUT FOR NOW...GUIDANCE
IDEA OF KEEPING THUNDERSTORM THREAT THROUGH THE WEEKEND IS ACCEPTED.
TEMPERATURES WILL REACH THE 80S EACH DAY WITH LOWS IN THE 60S TO
LOWER 70S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1045 PM CDT SUN JUN 16 2013

VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE TAF PERIOD. THE
EXCEPTION IS SOME PATCHY RADIATIONAL FOG THAT MAY DEVELOP AHEAD OF A
WEAK COLD FRONT ACROSS NORTHWEST IOWA LATE TONIGHT. MVFR VSBYS
ARE EXPECTED WITH ANY FOG THAT DOES DEVELOP...AND MAY AFFECT THE
KSUX TAF SITE. WINDS WILL TURN NW BEHIND THE FRONT FOR MONDAY.

&&

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

$$

SHORT TERM...MJ
LONG TERM...MJ/WILLIAMS
AVIATION...