Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 010826
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
326 AM CDT TUE SEP 1 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 325 AM CDT TUE SEP 1 2015

WARM AND HUMID CONDITIONS CONTINUE AS WE TURN THE PAGE TO SEPTEMBER
TODAY. WEAK STATIONARY BOUNDARY SOUTH CENTRAL SD INTO WEST CENTRAL
MN EARLY THIS MORNING WILL WASH OUT AS SOUTHERLY FLOW BECOMES MORE
ESTABLISHED ACROSS THE AREA THROUGH THE DAY. WILL CARRY A SMALL POP
IN THE FAR SOUTHWEST EARLY IN THE DAY FOR POSSIBLE ELEVATED SHOWERS
OR STORMS WORKING NORTH OUT OF CENTRAL NEBRASKA...THOUGH CURRENT
ACTIVITY HAS BEEN STRUGGLING TO MAKE MUCH PROGRESS THUS FAR. WILL
ALSO LEAVE A SMALL POP FARTHER EAST IN THE MISSOURI VALLEY LATE IN
THE DAY AS A MID LEVEL WAVE APPROACHES THE REGION IN SOUTHWEST FLOW
ALOFT. GENERALLY EXPECT DRY CONDITIONS TO PREVAIL THROUGHOUT THE
DAYTIME HOURS THOUGH...WITH SCATTERED CONVECTION MORE LIKELY ACROSS
SOUTHEAST HALF OF THE CWA TONIGHT AS THE AFOREMENTIONED WAVE SLIDES
NORTHEAST ACROSS THE AREA.

MAIN QUESTION OF THE DAY IS WHETHER ISOLATED-SCATTERED CONVECTION
WILL DEVELOP ACROSS WESTERN/NORTHERN PORTIONS OF THE FORECAST AREA
THIS AFTERNOON. LARGE SCALE MODELS DO NOT POINT IN THIS DIRECTION...
BUT HIGHER-RESOLUTION CONVECTION-ALLOWING MODELS...RAP/ARW/NMM...ALL
SEEM TO TRANSLATE THE CURRENT NEBRASKA CONVECTION NORTHEASTWARD INTO
OUR WESTERN COUNTIES THROUGH THE DAY. GIVEN THAT THESE MODELS ARE A
BIT TOO ROBUST/FAR NORTH WITH THEIR COVERAGE OF ONGOING ACTIVITY...
DO NOT HAVE A HIGH DEGREE OF CONFIDENCE IN THEIR EVOLUTION THROUGH
THE DAY AND THUS OPTED TO LEAVE WESTERN FORECAST AREA DRY FOR NOW.
WILL DEFINITELY BE SOMETHING TO WATCH FOR POSSIBLE UPDATES THOUGH...
AS NOT ONLY WOULD POPS NEED TO BE REDISTRIBUTED...BUT WOULD IMPACT
PROJECTED HIGHS AS WELL. GIVEN GENERALLY DRY FORECAST THROUGH THE
AFTERNOON...HAVE LEANED TOWARD THE MIDDLE TO WARM SIDE OF GUIDANCE
WITH HIGHS IN THE MID 80S TO AROUND 90. SOUTHERLY FLOW AND HUMID AIR
MASS SHOULD HOLD TEMPERATURES IN THE MID-UPPER 60S FOR LOWS TONIGHT.


.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 325 AM CDT TUE SEP 1 2015

LITTLE CHANGE TO THE EXTENDED WITH ABOVE NORMAL TEMPERATURES AND
HUMID CONDITIONS THROUGH THE REMAINDER OF THE WEEK AS UPPER LEVEL
RIDGING DOMINATES ACROSS THE REGION. IT WILL BE MAINLY DRY FOR
WEDNESDAY AND THURSDAY...OUTSIDE OF SLIGHT CHANCES IN OUR SOUTH AT
NIGHT...AND ACTUALLY LOWERED POPS A LITTLE FROM PREVIOUS FORECAST FOR
THOSE PERIODS WITH MOST MODELS NOW KEEPING CONVECTION OUT OF OUR
AREA.

MODEL CONSENSUS RAIN CHANCES GO UP FOR FRIDAY AND SATURDAY AS
SHORTWAVES EJECT OUT OF A WESTERN CONUS UPPER LEVEL TROUGH...THOUGH
STILL SEEING DIFFERENCES AMONG MODELS IN HANDLING THESE WAVES AS
THEY TRACK INTO THE NORTHERN PLAINS...SO CONFIDENCE IN SPECIFICS IS
NOT ESPECIALLY HIGH. GFS AND ECMWF ARE IN GENERAL AGREEMENT ON AN
UPPER LEVEL LOW OVER THE WESTERN U.S. TRACKING EASTWARD INTO THE
NORTHERN PLAINS/SOUTH CENTRAL CANADA BY THE END OF THE WEEKEND INTO
THE BEGINNING OF NEXT WEEK...THOUGH THE ECMWF STILL EXHIBITING A
SLOWER PROGRESSION OF THIS PROCESS. THIS IS ALSO REFLECTED IN THE
PASSAGE OF A FRONTAL BOUNDARY WITH MUCH COOLER AIR BEHIND IT..WHICH
THE GFS BRINGS THROUGH THE AREA BY SUNDAY NIGHT...WHEREAS THE ECMWF
HOLDS IT BACK ALMOST A FULL 24 HOURS. THAT MAKES FOR A TRICKY
TEMPERATURE FORECAST FOR LABOR DAY...WITH EITHER MID 70S OR MID 80S
BEING THE CASE DEPENDENT ON WHICH SOLUTION ENDS UP VERIFYING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1038 PM CDT MON AUG 31 2015

06Z TAFS WILL REFLECT PRIMARILY VFR CONDITIONS...EXCEPT STILL A
LITTLE CONCERNED ABOUT MVFR VISIBILITIES AT KFSD AND KSUX AROUND
SUNRISE DUE TO SMALL SURFACE DEW POINT DEPRESSIONS IN THIS HUMID
AIR MASS. IN ADDITION...THERE COULD BE SOME SCATTERED SHOWERS OR
THUNDERSTORMS NEAR THE KSUX TAF SITE TUESDAY EVENING. HOWEVER IT
WAS LATE ENOUGH IN THIS TAF PERIOD THAT I DID NOT WANT TO MENTION
IT AT THIS TIME DUE TO SOME UNCERTAINTY.


&&

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

$$

SHORT TERM...JH
LONG TERM...JM
AVIATION...MJ


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