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000
FXUS63 KFSD 281549
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
949 AM CST THU NOV 28 2013

.UPDATE...
ISSUED AT 949 AM CST THU NOV 28 2013

CLOUDS ARE PROVIDING THE GREATEST CHALLENGE FOR THE SHORT TERM
TODAY. FAIRLY EXTENSIVE CLOUDS PRESENT EARLY THIS MORNING HAVE
DIMINISHED IN COVERAGE EAST...BUT ARE FAIRLY SOLID FOR THE TIME
WEST. BASED ON KABR/KBIS MORNING RAOBS...THESE CLOUDS ARE FAIRLY
SHALLOW...BUT IMPRESSIVELY TRAPPED BELOW INVERSION...MAKING THE
DISSIPATION LIKELY TO BE A RESULT OF DRYING AND LIMITED HEATING
BELOW INVERSION AS WELL AS AN ADVECTIVE COMPONENT. RAP ON THE RIGHT
TRACK...BUT TOO PESSIMISTIC TOWARD I 29 CORRIDOR. AT THIS TIME...
CLOUDS LOOK TO BE FAIRLY TOUGH TO SHAKE IN THE WEST/SOUTHWEST CWA
WHILE THOSE AREAS IN ADVANCE OF THE LOW LEVEL RIDGE AXIS FROM
AROUND I29 EASTWARD ARE CERTAIN TO FIND A MIX OF CLOUDS AND SUN
THROUGH MIDDAY AND THEN TRENDING TOWARD MORE SUN. BASED ON TEMPS
ON CLOUD BEARING LEVEL AS WELL AS UPSTREAM OBSERVATIONS...HAVE
ADDED IN A FEW FLURRIES TO AREAS AS FAR SOUTH AS AROUND KFSD...BUT
EXPECT STRONGER COVERAGE OF LOW REFLECTIVITIES ON KABR RADAR TO
DWINDLE SOMEWHAT WITH INCREASING DISTANCE FROM WEAK TERRAIN
SUPPORT. EARLIER FLURRIES IN SW MN COULD HAVE IMPACTED SOMEWHAT
MORE RAPID DISSIPATION IN CLOUDS...AND MAY ALSO INFLUENCE THE
CLEARING TREND. TEMPS ALSO CHALLENGING WITH CONTINUED LOW LEVEL
COLD AIR ADVECTION...BUT TEMPS ALREADY REACHING INDICATED MIXING
POTENTIAL UNDER CLOUDY AREAS BY MID MORNING. PROBABLY NOT MUCH
ROOM TO WARM MORE THAN A FEW DEGREES ANYWHERE TODAY...MOST SO IN
AREAS WITH SUNSHINE TO THE EAST. UPDATES OUT.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 520 AM CST THU NOV 28 2013

CURRENT SURFACE ANALYSIS SHOWS THE FRONTAL BOUNDARY HAVING PUSHED
THROUGH OUR CWA EARLY THIS MORNING...WITH AN AREA OF STRATUS
STREAMING INTO OUR WESTERN CWA BEHIND THE EXITING SYSTEM. THE
SURFACE RIDGE AXIS PRESENTLY LOCATED THROUGH THE WESTERN PORTIONS OF
THE DAKOTA WILL SLIDE TO THE SOUTH AND EAST TODAY...AND WITH DRYING
AND SUBSIDENCE LOOKING FOR THE LOW CLOUDS TO THIN OUT ACROSS THE
AREA BY LATE MORNING OR EARLY AFTERNOON. OTHERWISE...IT WILL BE
BREEZY DURING THE EARLY PART OF THE DAY...ESPECIALLY IN THE
EAST...WITH COLD AIR ADVECTION AND A DECENT GRADIENT ACROSS THE
AREA...THEN TAPERING DOWN IN THE AFTERNOON AS HIGH PRESSURE BUILDS
IN AND THE GRADIENT RELAXES AND ML WINDS DECREASE. THERMAL PROFILES
DO COOL A BIT TODAY...THOUGH NOTHING TOO EXTREME WITH HIGHS STILL
MAKING IT INTO THE MID 20S TO LOWER 30S FROM NORTHEAST TO SOUTHWEST
RESPECTIVELY.

THE HIGH PRESSURE MOVES QUICKLY TO THE EAST TONIGHT...AND WITH THAT
WINDS WILL TRANSITION TO SOUTHEASTERLY AND PICK UP LATER AT NIGHT.
IT WILL STILL BE A COLD NIGHT WITH LOWS IN THE UPPER SINGLE DIGITS
TO TEENS...WITH TEMPS STEADYING OUT OR RISING SOME LATE AT NIGHT AS
THE WINDS INCREASE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 520 AM CST THU NOV 28 2013

POTENT PACIFIC LOW DIVES INTO THE PACIFIC NORTHWEST FRIDAY AND
SATURDAY...SHIFTING THE INTERMOUNTAIN WEST RIDGING ITO THE PLAINS
STATES. A STRONG PUSH OF WARM AIR ADVECTION AND BREEZY SOUTHERLY
WINDS WILL BRING MILDER TEMPERATURES ON FRIDAY DESPITE SOME PASSING
MID AND HIGH CLOUDS FILTERING THE SUNSHINE. HIGHS WILL WARM TO
SLIGHTLY ABOVE NORMAL READINGS IN THE LOW 30S EAST TO THE MID 40S
WEST. A WEAK FRONT SAGS ACROSS THE FORECAST AREA FRIDAY NIGHT
THROUGH SATURDAY MORNING...BUT WITHOUT MOISTURE OR A REAL COLD AIR
PUSH BEHIND IT...CONDITIONS WILL REMAIN DRY AND MILD WITH HIGHS
MIXING INTO THE UPPER 30S TO MID 40S.

MUCH GREATER UNCERTAINTY SHOWS UP EARLY NEXT WEEK AS THE PACIFIC
TROUGH STRENGTHENS AND MOVES INTO THE NORTHERN ROCKIES. MODELS STILL
SHOWING SIGNIFICANT DIFFERENCES IN THE STRENGTH...TIMING AND TRACK
OF THE UPPER LOW. THE GFS FOLLOWS A MORE NORTHERLY TRACK WHILE THE
ECMWF IS SLOWER AND FURTHER SOUTH. FINALLY...THE CANADIAN DEPICTS A
MUCH WEAKER SYSTEM OVERALL WHICH GIVEN THE ENERGETIC NATURE OF THIS
SYSTEM SEEMS THE LEAST LIKELY.

INITIAL SHORTWAVE AHEAD OF THE MAIN SYSTEM SLIDES SOUTHEAST ACROSS
THE REGION AROUND THE SUNDAY NIGHT/MONDAY TIME FRAME. WITH THE GFS
RAPIDLY AMPLIFYING THE PAC NW TROUGH AND UPPER RIDGE AHEAD OF
IT...THIS WAVE IS WEAKER AND FASTER MOVING THAN THE ECMWF WHICH
DEVELOPS AN INVERTED TROUGH FEATURE OVER THE NORTHERN AND CENTRAL
PLAINS AND KEEPS IT IN THE PICTURE WELL INTO TUESDAY. SIGNIFICANT
DIFFERENCES IN TEMPERATURE PROFILES ALSO MAKE PRECIPITATION TYPES
DIFFICULT TO PINPOINT. TEMPERATURES LOOK TO REMAIN SEASONALLY MILD
THROUGH WEDNESDAY WITH MUCH COOLER READINGS ARRIVING LATE IN THE
WEEK. FOR NOW WILL KEEP MENTION OF BOTH RAIN AND SNOW. NOT MUCH
CONFIDENCE IN THE TIMING OF THE PRECIPITATION BUT CHANCES DO APPEAR
TO IMPROVE AS WE MOVE TOWARDS MID WEEK AS THE MAIN PACIFIC TROUGH
ADVANCES TOWARDS THE REGION. FOR NOW DID NOT ALTER THE ALLBLEND POPS
OR TEMPS MUCH GIVEN SUCH UNCERTAINTY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 520 AM CST THU NOV 28 2013

STRATUS CONTINUES TO EXPAND SOUTHWARD BEHIND EXITING COLD
FRONT...AND THE CHALLENGE BECOMES WHEN THIS AREA OF LOW CLOUDS
WILL BREAK UP. WITH HIGH PRESSURE BUILDING ACROSS THE REGION AND
ASSOCIATED SUBSIDENCE AND DRYING...WOULD EXPECT CLOUDS TO BEGIN TO
DISSIPATE BY MID AFTERNOON. THERE IS SOME DISAGREEMENT AMONG
MODELS...WITH THE RAP HOLDING IT IN THROUGH AT LEAST LATE
AFTERNOON. AT THIS POINT WILL LEAN A LITTLE EARLIER WITH CLOUDS
SCATTERING OUT MOST PLACES AFTER AROUND 19Z. OTHERWISE...NORTHWESTERLY
WINDS...GUSTY AT TIMES EARLY...WILL TAPER DOWN...BECOMING LIGHT BY
THIS EVENING.


&&

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

$$

UPDATE...CHAPMAN
SHORT TERM...
LONG TERM...JM
AVIATION...JM