Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 181142
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
642 AM CDT FRI APR 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 351 AM CDT FRI APR 18 2014

EXTENSIVE MID LEVEL CLOUDS ACROSS THE NORTHEAST HALF OF THE CWA
EARLY THIS MORNING...WITH ADDITIONAL HIGHER MID CLOUDS IN CENTRAL
PORTIONS OF SOUTH DAKOTA. LITTLE IN THE WAY OF MENTIONABLE PRECIP
COMING OUT OF EITHER BAND OF CLOUDS. POSSIBLY A FEW SPRINKLES IN OUR
FAR NORTHEAST CWA AROUND KMML/KTKC WHERE LOWEST CLOUD HEIGHTS HAVE
DIPPED TO AROUND 5KFT...BUT THIS HAS BEEN SLOWLY SHIFTING EAST AND
IS EXPECTED TO BE OUT OF THE CWA BEFORE START OF THE VALID FORECAST
PERIOD. THUS HAVE REMOVED OUR LOW POPS FROM THE MORNING HOURS...WITH
ATTENTION THEN FOCUSED ON INCREASING SOUTHERLY WINDS AND ASSOCIATED
BEGINNING OF WELL-ADVERTISED WARMING TREND. EXPECT A STRONG MIXING
DAY...ESPECIALLY IN OUR WEST AS THE SURFACE RIDGE SHIFTS EAST TODAY.
RAP HAS TENDED TO HANDLE THE STRONG MIXING WELL IN RECENT WARM DAYS
AND OUR GOING FORECAST WAS WELL SUPPORTED BY LATEST RAP AS WELL AS
BIAS-CORRECTED GRIDS FOR TEMPERATURES TODAY...SO MADE ONLY MINOR
CHANGES.

WITH THE STRONG MIXING...MOS GUIDANCE TENDS TO PERFORM BETTER FOR
PROJECTED WIND SPEEDS...AND THIS SUPPORTS BUMPING SPEEDS UP A BIT
ACROSS MY WEST THIS AFTERNOON...WITH MUCH OF OUR WEST PUSHING INTO
LOWER END OF WIND ADVISORY RANGE IN THE AFTERNOON/EARLY EVENING.
AFTER COORDINATION WITH WFO ABERDEEN...OPTED TO ISSUE WIND ADVISORY
ALONG AND WEST OF A LINE FROM BON HOMME TO KINGSBURY COUNTY. STRONG
WINDS AND MILD TEMPERATURES WILL RESULT IN VERY HIGH FIRE DANGER
OVER MOST OF THE CWA...WITH EXCEPTION IN EXTREME NORTHEAST AREAS.
WINDS IN MY WEST WOULD BE SUPPORTIVE OF RED FLAG...HOWEVER MODEST
LOW LEVEL MOISTURE ADVECTION IN INCREASING SOUTHERLY FLOW EXPECTED
TO SOMEWHAT OFFSET MIXING DOWN OF DRIER AIR...AND MINIMUM HUMIDITY
LEVELS ARE HOLDING ABOVE RED FLAG CRITERIA AS A RESULT. DAY SHIFT
WILL WANT TO WATCH THIS CLOSELY HOWEVER...AS WEAKER ADVECTION OR
GREATER MIX-DOWN OF DRY AIR FROM ALOFT COULD PUSH THESE HUMIDITY
LEVELS CLOSER TO 20 PERCENT IN OUR SOUTHWEST CORNER...WHICH IS THE
AREA OF GREATEST CONCERN FROM A WIND STANDPOINT.

FOR TONIGHT...BREEZY CONDITIONS CONTINUE AHEAD OF THE APPROACHING
TROUGH/MID LEVEL WAVE...ENHANCED BY INCREASING LOW LEVEL JET ACROSS
THE REGION. SURFACE BOUNDARY PUSHES INTO OUR NORTHWEST CORNER LATE
TONIGHT...AND WILL CONTINUE SOME LOW POPS JUST AHEAD OF THE BOUNDARY
WITH DECENT LOW LEVEL MOISTURE TRANSPORT...WEAK LIFT FROM TAIL END
OF THE MID LEVEL WAVE...AND POSSIBLY SOME WEAK ELEVATED INSTABILITY
AS INDICATED BY NAM ACROSS THE NORTHWEST 1/3 OF THE CWA AFTER 06Z.
CONTINUE TO SEE FAIRLY DRY AIR MASS BELOW 700MB...SO NOT CONVINCED
WE WILL SEE MUCH PRECIP REACH THE GROUND...AND COVERAGE EXPECTED TO
BE FAIRLY SPOTTY IN THE PRE-DAWN HOURS...BUT CERTAINLY WORTH KEEPING
A MENTION IN THE FORECAST. LOWS SHOULD REMAIN QUITE MILD IN THE DEEP
SOUTHERLY FLOW...GENERALLY A DEGREE OR TWO EITHER SIDE OF 50 IN MOST
AREAS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 351 AM CDT FRI APR 18 2014

THE COLD FRONT WILL CONTINUE TO PUSH ACROSS THE AREA ON SATURDAY.
KEPT ONLY SMALL CHANCES OF PRECIPITATION WITH THE SYSTEM WITH ONLY
WEAK LOW LEVEL CONVERGENCE...LIMITED MOISTURE...AND BETTER UPPER
LEVEL FORCING REMAINING TO THE NORTH OF OUR AREA. STRONG SOUTHERLY
FLOW OUT AHEAD OF THE FRONT WILL BRING HIGHS INTO THE MID AND UPPER
70S THROUGH THE SOUTHEASTERN PORTIONS OF THE CWA...WHILE AREAS BEHIND
THE FRONT WILL TOP OUT NEAR 70. THE FRONT NEVER REALLY MAKES IT OUT
OF OUR AREA ON SATURDAY...STALLING ACROSS NORTHWEST IOWA ON SATURDAY
NIGHT INTO SUNDAY. THIS WILL BE THE FOCUS FOR SHOWER AND
THUNDERSTORM ACTIVITY THROUGH THE PERIOD AS A SHORTWAVE LIFTS UP
INTO THE REGION ON A SOUTHWESTERLY UPPER LEVEL FLOW. CAPE AND
EFFECTIVE SHEAR VALUES REMAIN UNIMPRESSIVE...SO NOT EXPECTING ANY
SEVERE STORMS FOR SATURDAY NIGHT AND SUNDAY. WIDE RANGE OF
TEMPERATURES ACROSS THE AREA FOR SATURDAY NIGHT...WITH LOWS RANGING
FROM NEAR 40 OVER OUR NORTH AND EAST WHERE LESS CLOUD COVER WILL
RESIDE AND COLD AIR ADVECTION BEHIND THE FRONT WILL BE MORE
APPARENT...TO THE LOWER 50S THROUGH THE SOUTHEAST. TEMPERATURES
SOMEWHAT TRICKY FOR SUNDAY DEPENDENT ON WHERE CLOUD COVER/SHOWERS
EXIST...BUT SHOULD WARM INTO THE LOWER/MID 70S OVER MUCH OF THE
AREA...EXCEPT FOR MID/UPPER 60S IN THE FAR SOUTHEAST WHERE THERE IS
A MORE LIKELY PROBABILITY THAT IT WILL BE CLOUDY IN CONJUNCTION WITH
AN EASTERLY SURFACE FLOW.

THE SHORTWAVE AND STALLED FRONTAL BOUNDARY WILL PULL OFF TO THE EAST
BY MONDAY...LEADING TO A DRY AND PLEASANT DAY WITH HIGHS GENERALLY
UPPER 60S TO LOWER 70S. INTO THE EXTENDED...TUESDAY THROUGH
THURSDAY...PRECIPITATION CHANCES LOOK TO RAMP BACK UP BY MIDWEEK AS A
WESTERN U.S UPPER LEVEL TROUGH BEGINS TO MOVE EASTWARD...AND A WARM
FRONT LIFTS UP INTO THE AREA SOMETIME IN THE WEDNESDAY TIME FRAME.
THIS TO BE FOLLOWED BY A COLD FRONTAL PASSAGE LATER IN THE PERIOD.
MODELS NOT IN THE GREATEST OF AGREEMENT WITH THE SPECIFICS OF HOW
THIS SYSTEM EVOLVES...BUT THUNDERSTORM CHANCES LOOK PRETTY DECENT
WITHIN THE TIME PERIOD BORDERED BY TUESDAY NIGHT INTO THURSDAY.
TEMPERATURES LOOK TO REMAIN ABOVE NORMAL THROUGH THE EXTENDED.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 642 AM CDT FRI APR 18 2014

INCREASINGLY GUSTY SOUTHEAST-SOUTH WINDS WILL BE PRIMARY AVIATION
CONCERN THROUGH THE PERIOD. GUSTS IN EXCESS OF 25KT EXPECTED WEST OF
HIGHWAY 81 AFTER 15Z...WITH GUSTS IN 30-37KT RANGE IN THESE AREAS
AFTER 18Z...SPREADING INTO I-29 CORRIDOR NEAR AND NORTH OF KFSD BY
LATE AFTERNOON. GUSTS WILL SUBSIDE SLIGHTLY TOWARD SUNSET...THOUGH
WINDS WILL REMAIN BREEZY THROUGHOUT THE OVERNIGHT HOURS AS SOUTH TO
SOUTHWEST LOW LEVEL JET INCREASES TO 50-60KT ABOVE ROUGHLY 1500FT.
WHILE WINDS OFF THE SURFACE WILL BE VERY STRONG TONIGHT...FORECAST
SOUNDINGS DEPICT LITTLE VARIANCE IN DIRECTION WITH GRADUAL INCREASE
IN WIND SPEED THROUGH THE LOWEST 2KFT...SO OPTED TO LEAVE MENTION OF
LOW LEVEL WIND SHEAR OUT OF THIS FORECAST.

ASIDE FROM THE WINDS...VFR CONDITIONS ARE EXPECTED THROUGH THE
FORECAST PERIOD. COOL FRONT APPROACHING KHON AREA AFTER 19/06Z WITH
SOME INDICATION OF WEAK ELEVATED INSTABILITY. CANNOT RULE OUT AN
ISOLATED SHOWER OR THUNDERSTORM ASSOCIATED WITH THIS BOUNDARY...BUT
LIMITED COVERAGE AND UNCERTAINTY IN TIMING PRECLUDES MENTION IN THE
TAF. GREATER CONCERN FROM ANY VIRGA/SPOTTY SHOWER WOULD BE MIXING OF
STRONGER WINDS ALOFT TO THE SURFACE.

&&

.FIRE WEATHER...
ISSUED AT 351 AM CDT FRI APR 18 2014

SOUTHERLY FLOW WILL INCREASE THROUGHOUT THE MORNING...BECOMING
RATHER GUSTY THIS AFTERNOON...ESPECIALLY ALONG AND WEST OF THE JAMES
RIVER VALLEY...WHERE SUSTAINED WINDS OF 25 TO 30 MPH AND OCCASIONAL
GUSTS OF 40 TO 45 MPH ARE ANTICIPATED. THIS WILL BRING MUCH WARMER
AIR BACK INTO THE REGION...WITH AFTERNOON TEMPERATURES EXPECTED TO
RANGE FROM UPPER 50S AND LOWER 60S IN SOUTHWEST MINNESOTA...TO THE
LOWER TO MID 70S NEAR AND WEST OF THE JAMES RIVER. THIS WILL LEAD TO
VERY HIGH FIRE DANGER ACROSS MOST OF THE AREA...AND WILL BE WATCHING
HUMIDITY LEVELS CLOSELY THROUGH THE LATE MORNING/EARLY AFTERNOON. AT
THIS TIME...DEW POINTS ARE PROJECTED TO CLIMB INTO THE MID TO UPPER
30S...WHICH WOULD KEEP MINIMUM HUMIDITY LEVELS GENERALLY IN THE 25
TO 35 PERCENT RANGE ACROSS SOUTH CENTRAL/SOUTHEAST SOUTH DAKOTA...
NORTHEAST NEBRASKA AND NORTHWEST IOWA. HOWEVER...IF THESE DEW POINTS
DO NOT RISE AS EXPECTED...THE LOWER BRULE AREA AND POSSIBLY PORTIONS
OF THE JAMES RIVER VALLEY COULD SEE HUMIDITY LEVELS REACH CRITICAL
VALUES OF 25 PERCENT OR LOWER.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY FROM NOON TODAY TO 8 PM CDT THIS EVENING FOR
     SDZ038-039-050-052>054-057>060-063>065-068.

MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...JH
LONG TERM...JM
AVIATION...JH
FIRE WEATHER...JH








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