Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 310841
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
341 AM CDT MON AUG 31 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CDT MON AUG 31 2015

WARM...HUMID AND SOMEWHAT BREEZY DAY IN STORE FOR THE REGION AHEAD
OF WEAK COOL FRONT...PROGGED TO PUSH INTO WESTERN PORTIONS OF THE
FORECAST AREA THIS AFTERNOON. CONTINUES TO LOOK LIKE THE FRONT WILL
ENTER THE AREA DRY AS LIMITED MOISTURE BELOW 10KFT ALLOWS STRONG CAP
TO REMAIN IN PLACE. EXPECT HIGHS TO RANGE FROM LOWER 80S NEAR/EAST
OF I-29...TO NEAR 90 WHERE MIXING IS MAXIMIZED IN THERMAL RIDGE JUST
AHEAD OF THE BOUNDARY.

FRONT STALLS NEAR LAKE ANDES TO KBKX/KMML LINE OVERNIGHT...WITH
HUMID AIR MASS HOLDING TEMPERATURES IN THE LOWER-MID 60S TONIGHT...
OR AROUND 10 DEGREES ABOVE NORMAL LOW TEMPERATURES FOR THE 1ST OF
SEPTEMBER. MOISTURE STILL SOMEWHAT LACKING BETWEEN THE ABUNDANT
SURFACE HUMIDITY AND MID LEVELS...BUT WITH WEAK DESTABILIZATION AS
MID LEVEL WAVE APPROACHES FROM THE SOUTHWEST...THINK WE COULD SEE A
FEW ACCAS SHRA/TSRA DEVELOP LATE TONIGHT AND HAVE ADDED A LOW POP TO
SOUTHWEST PORTIONS OF THE CWA AFTER 06Z.


.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 340 AM CDT MON AUG 31 2015

WITH UPPER LEVEL RIDGING DOMINATING ACROSS THE REGION...THE EXTENDED
PERIOD WILL BE CHARACTERIZED BY ABOVE NORMAL TEMPERATURES AND
PERIODIC LOW END RAIN CHANCES INTO FRIDAY. THIS WILL PLAY OUT TO
HIGHS GENERALLY MID 80S TO LOWER 90S AND LOWS IN THE UPPER 60S.

IN THE NEARER TERM...LEFT TUESDAY DRY AS THE BOUNDARY WASHES OUT
OVER OUR AREA. ON TUESDAY NIGHT THETA E ADVECTION AND INSTABILITY
INCREASES ACROSS THE AREA AS A SHORTWAVE LIFTS INTO THE REGION AND A
LOW LEVEL JET DEVELOPS AND FOCUSES THROUGH THE SOUTHEASTERN PORTIONS
OF THE CWA OVERNIGHT. RELATIVE TO THAT...KEPT SMALL THUNDERSTORM
CHANCES THROUGH OUR LOWER MO RIVER VALLEY AND NORTHWESTERN IOWA
ZONES DURING THAT TIME FRAME. LOOKS TO BE A REPEAT PERFORMANCE ON
WEDNESDAY NIGHT WITH THUNDERSTORM CHANCES OVER OUR SOUTHEASTERN
ZONES.

BETTER THUNDERSTORM CHANCES THEN COME INTO PLAY BY FRIDAY NIGHT AND
INTO NEXT WEEKEND AS AN UPPER LEVEL TROUGH OVER THE WESTERN CONUS
BEGINS TO NUDGE EASTWARD...AS SHORTWAVES EJECT OUT OF THE TROUGH AND
INTO OUR AREA. MODEL DIFFERENCES ALSO BEGIN TO GROW TOWARD THE END
OF THE EXTENDED...MOST NOTICEABLE WITH THE TIMING OF A FRONTAL
PASSAGE SOMETIME IN THE SATURDAY TO MONDAY TIME FRAME...WITH THE GFS
MUCH QUICKER THAN THE ECMWF. THIS WILL PUT AN END TO THE ABOVE
NORMAL TEMPERATURES AS MUCH COOLER AIR FILTERS IN BEHIND THE
SYSTEM...THOUGH CONFIDENCE LOW ON WHAT DAY THIS WILL ACTUALLY HAPPEN
WITH MODEL TIMING DIFFERENCES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1044 PM CDT SUN AUG 30 2015

CONFIDENCE IS NOT HIGH FOR THE FORTHCOMING 06Z TAF SET...
ESPECIALLY FOR KFSD AND KSUX. ONCE AGAIN...CONCERNED ABOUT STRATUS
FOR KFSD AND KSUX. IN FACT KFSD HAS CURRENTLY DEVELOPED AN IFR
DECK WHICH ONE CANNOT SEE OF THE IR FOG CURVE DUE TO THE AMOUNT OF
CIRRUS CURRENTLY OVER THE AREA. JUDGING FROM OBSERVATIONS IT IS
NOT VERY WIDESPREAD YET...BUT COULD BE AS THE NIGHT PROGRESSES.
THEREFORE KEPT THESE CEILINGS AS BROKEN FOR MUCH OF THE REST OF
THE NIGHT. LIKEWISE AT KSUX...WHO COULD VERY WELL SEE IFR
CONDITIONS THEMSELVES DEVELOP LATER TONIGHT WITH DENSE FOG NOT TOO
FAR TO THEIR SOUTH. THEY WILL BE MONITORED CLOSELY FOR LIFR
CONDITIONS. KHON SHOULD STAY VFR TONIGHT AND CONTINUED TO LEAVE
OUT LOW LEVEL WIND SHEAR FOR THAT LOCATION WITH WELL MIXED WINDS
AT THE SURFACE.


&&

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

$$

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


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