Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 250924
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
424 AM CDT SAT APR 25 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 423 AM CDT SAT APR 25 2015

COMPLICATED FORECAST FOR TODAY AS SPORADIC SHOWERS CONTINUE TO
DEVELOP ACROSS THE AREA.  ACTIVITY IS MOVING VERY LITTLE...AND IF
ANYTHING...IS DRIFTING SLIGHTLY WESTWARD WITH LOW LEVEL WINDS OUT OF
THE SOUTHEAST.  WINDS IN THE MID LEVELS OF THE ATMOSPHERE ARE QUITE
LIGHT...LEADING TO VERY LITTLE MOVEMENT.  CURRENTLY...LARGE COMPLEX
OF STORMS ACROSS SOUTHEAST NEBRASKA INTO SOUTHERN IOWA ROTATING
AROUND AN UPPER LEVEL LOW.  COULD SEE A FEW SHOWERS DEVELOP THROUGH
15Z OR SO ACROSS NORTHWEST IOWA...OTHERWISE..EXPECT THE BULK OF THE
ACTIVITY TO REMAIN TO THE SOUTH.  WEAK BAND OF FRONTOGENETIC FORCING
EXTENDING NORTHWARD THROUGH THE JAMES VALLEY THIS MORNING LEADING TO
A FEW LIGHT SHOWERS.  THESE SHOWERS ARE EXPECTED TO CONTINUE TO
RETROGRADE BACK TO THE WEST THROUGH THE MORNING HOURS.  AS THE UPPER
LEVEL LOW TO THE SOUTH CONTINUES TO SLIDE EAST AS WEAK UPPER LEVEL
RIDGE MOVES INTO THE AREA...EXPECT SHOWER POTENTIAL TO BREAK DOWN
WITH OVERALL SUBSIDENCE AND FORECAST AREA TO REMAIN DRY THROUGH MOST
OF THE DAY.  MODEL SOUNDINGS SUGGEST THAT THE STRATUS ACROSS THE
AREA MAY TRY TO THIN THROUGHOUT THE DAY...AND HAVE SIDED WITH
CONSENSUS FOR HIGHS.  THE ARW HAS SHOWERS CONTINUING ACROSS CENTRAL
SOUTH DAKOTA THROUGH MUCH OF THE DAY...LEADING TO COOLER
TEMPERATURES ACROSS CENTRAL SOUTH DAKOTA.  CONFIDENCE IS LOW AS TO
WHEN THESE SHOWERS WILL END...AND WHAT IMPACT THEY WILL HAVE ON HIGH
TEMPERATURES.

DRIER AIR IS EXPECTED TO FILTER INTO THE REGION TONIGHT LEADING TO
CLEARING FROM EAST TO WEST. THIS WILL ALLOW LOCATIONS IN THE EAST TO
RADIATE BETTER...BUT STILL EXPECT TEMPERATURES TO REMAIN ABOVE
FREEZING IN THE 30S TO MID 40S.


.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 423 AM CDT SAT APR 25 2015

RETURN TO QUIETER AND SOMEWHAT MORE CLEARCUT FORECAST FOR THE MIDDLE
TO LONGER RANGES. NEXT WEEK WILL BEGIN WITH WEAK UPPER RIDGING OVER
THE REGION...PROVIDING CLEAR SKIES AND SEASONABLY MILD TEMPERATURES.
WITH AMPLE SUNSHINE EXPECTED SUNDAY AND MONDAY...FAVORED WARMER END
OF GUIDANCE TEMPERATURES FOR HIGHS. HOWEVER...WITH THE RECENT RAIN
AND LACK OF GOOD DRYING CONDITIONS TODAY...DID HOLD HIGHS BELOW BIAS
CORRECTED VALUES WHICH ARE DOMINATED BY THE DRY CONDITIONS PRIOR TO
FRIDAYS RAINFALL. THIS ESPECIALLY TRUE MONDAY WHEN MIXING WILL BE
MORE LIMITED WITHIN THE SURFACE RIDGE AXIS ACROSS THE AREA.

WEAK WAVE AND ASSOCIATED FRONT CROSS THE REGION MONDAY NIGHT/TUESDAY
BUT MOISTURE WITH THIS WAVE APPEARS TO BE SOMEWHAT LIMITED AT THIS
POINT. WILL HANG ON TO LOW POP NORTH OF I-90 AS ECMWF/GEM CONTINUE
TO INDICATE A LITTLE DEEPER MOISTURE AND POTENTIAL FOR SOME LIGHT
SHOWERS OR SPRINKLES...BUT MOST AREAS WILL LIKELY REMAIN DRY.
OTHERWISE THE MIDDLE TO LATTER PART OF NEXT WEEK WILL FEATURE A
GRADUAL WARMING TREND AS BROAD RIDGE TAKES SHAPE ACROSS THE PLAINS.
ECMWF TRACKS A BIT STRONGER WAVE THROUGH THE RIDGE BY THURSDAY NIGHT
OR FRIDAY...AND DECIDED TO HANG ON TO LOW GUIDANCE POPS ACROSS OUR
NORTHEAST TO ACCOUNT FOR THIS POSSIBILITY ON FRIDAY...BUT GENERALLY
LOOKS LIKE A DRY PATTERN THROUGH THE BULK OF NEXT WEEK.

WILL HAVE TO WATCH FOR INCREASING FIRE DANGER AGAIN BY LATE IN THE
WEEK...AS SURFACE RIDGE SHIFTS EAST AND STRONGER SOUTHERLY FLOW
RETURNS TO THE REGION. MODELS CURRENTLY INDICATE MODEST HUMIDITY
LEVELS ACCOMPANYING THE SOUTHERLY FLOW...WITH ECMWF MORE
AGGRESSIVE WITH A MOISTURE RETURN BY THURSDAY THAN THE GEM/GFS.
LOW CONFIDENCE THAT THE MOISTURE WILL ACTUALLY RETURN THAT QUICKLY
GIVEN SURFACE RIDGE STILL BETWEEN HERE AND THE GULF OF MEXICO.
THUS NUDGED DEW POINTS DOWN A BIT TOWARD THE RAW GEM/GFS VALUES
FOR THURSDAY. THIS CURRENTLY LEADING TO MODERATE TO HIGH FIRE
DANGER FOR THURSDAY AND FRIDAY...BUT COULD BE HIGHER IF MOISTURE
IS SLOWER TO RETURN.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1035 PM CDT FRI APR 24 2015

WEAK VORTICITY MAX CONTINUES TO ROTATE THROUGH THE CWA LATE THIS
EVENING. AT THE SURFACE...WARM FRONT CONTINUES TO RETREAT
SOUTHWEST ALLOWING COOLER AND MORE STABLE AIR TO FILTER WESTWARD.
HOWEVER...EXPECTING HIT OR MISS SCATTERED SHOWERS AND
THUNDERSTORMS TO CONTINUE TO PERCOLATE THROUGH THE OVERNIGHT
HOURS.

MVFR AND EVENTUALLY IFR CEILINGS WILL SETTLE INTO THE REGION FOR
THE REMAINING OVERNIGHT HOURS AND FIRST HALF OF SATURDAY. AS DRIER
AIR FILTERS IN FROM THE NORTHEAST...WE WILL SEE THESE CEILINGS
IMPROVE TOWARDS MIDDAY.


&&

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

$$

SHORT TERM...
LONG TERM...JH
AVIATION...DUX


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