000
FXUS63 KFSD 050942
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
342 AM CST THU MAR 5 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 342 AM CST THU MAR 5 2015

WARMING WILL BEGIN SURFACE AND ALOFT TODAY AS HIGH PRESSURE OVER THE
AREA MOVES EAST. CANADIAN SHORT WAVE PASSING THE SOUTHWEST FLANK OF
THE AREA LATER TODAY WILL HAVE VERY LITTLE MOISTURE TO WORK WITH AND
SHOULD PRODUCE NO MORE THAN A SLIGHT INCREASE IN CLOUDS...MAINLY AT
MID LEVELS. SURFACE TEMPERATURES UNDER THE MARCH SUN SHOULD WARM MORE
THAN GUIDANCE...EVEN NOT COUNTING THE MET WHICH IS WOEFULLY
UNDERDONE...REFLECTING OF COURSE THE NAM LOW LEVELS. STILL...HAVE
SNIPPED A DEGREE OR TWO OFF PREVIOUS FORECAST IN THE EAST. HIGHS
WILL RANGE FROM THE 20S EAST TO AROUND 40 SOUTHWEST.

TONIGHT WILL SEE CONTINUED WARMING AND ONLY A VERY LIMITED EVENING
DROP IN TEMPERATURES. CLOUDS MAY DECREASE A LITTLE THEN INCREASE A
LITTLE BUT WILL KEEP SKIES PARTLY CLOUDY. A MODEST SOUTHERLY BREEZE
WILL TREND TO SOUTHWESTERLY...REFLECTING THE WARMING GOING ON.
SURFACE TEMPERATURES WILL NOT RISE MUCH AFTER THE EVENING DROP BUT
THEY CERTAINLY WILL NOT FALL LATE TONIGHT UNDER THE STRENGTH OF THE
LOW LEVEL WARMING.


.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 342 AM CST THU MAR 5 2015

WARMING TEMPERATURE TRENDS ARE THE FOCUS FOR THIS FORECAST PERIOD. A
LITTLE DISAGREEMENT IN THE MODELS REGARDING HOW QUICKLY THE WARMER
LOW LEVEL AIR WILL WORK BACK INTO THE REGION...WITH GFS HOLDING ON
TO SUB-ZERO 925MB TEMPERATURES ACROSS OUR NORTHEAST CWA THROUGH THE
AFTERNOON FRIDAY WHILE THE ECMWF WARMS THE SAME LAYER ANOTHER 7C.
NAM PLAYING THE MIDDLE GROUND...THOUGH BOTH NAM AND GFS CONTINUE
TO WARM THROUGH THE EVENING AHEAD OF A WEAK MID LEVEL WAVE
DROPPING INTO THE AREA. THINK THE GFS HOLDS ON TO THE COLD AIR TOO
LONG...BUT GIVEN SNOW COVER ACROSS OUR NORTH AND EAST...HAVE SIDED
CLOSER TO THE MIDDLE GROUND WITH UPPER 30S IN THOSE AREAS...WHILE
FAVORING THE WARMER GUIDANCE IN THE LOWER-MID 50S ACROSS OUR
SOUTHWEST.

NOT A GREAT DEAL OF MOISTURE BENEATH MID CLOUD DECK FOR WAVE TO WORK
WITH AS IT MOVES THROUGH THE REGION LATE FRIDAY NIGHT/SATURDAY
MORNING...BUT SLIGHTLY BETTER LOW LEVEL SATURATION ACROSS OUR FAR
NORTHEAST COULD SUPPORT SOME VERY LIGHT PRECIP REACHING THE SURFACE
AS COOLER AIR SINKS IN BEHIND THE WAVE. PRECIP MAY INITIALLY FALL
INTO WARM LAYER ABOVE FREEZING...BUT THIS LAYER ALSO DRY AND WET
BULB POTENTIAL SHOULD COOL ENOUGH TO SUPPORT MAINLY SNOW IF ANY OF
THE PRECIP DOES REACH THE GROUND.

SATURDAY REMAINS FAIRLY CLOUDY ACROSS THE NORTHEAST AHEAD OF A
SECOND WAVE SLATED TO SLIDE THROUGH THE REGION SATURDAY NIGHT.
SIMILAR TO FIRST WAVE...PLENTY OF MID LEVEL MOISTURE WITH SUB-CLOUD
MOISTURE INITIALLY LACKING. TOUGH TO IGNORE POTENTIAL THOUGH...WITH
ALL MODELS SQUEEZING OUT SOME LIGHT QPF...SO HAVE ADDED A SMALL POP
TO OUR NORTHEAST HALF SATURDAY NIGHT AS WELL. GFS/NAM INDICATE QPF
CLOSER TO THE MISSOURI RIVER VALLEY...BUT SEEING DEEPER SATURATION
ACROSS THE NORTHEAST SO WILL KEEP THE LOW POP CONFINED THERE FOR NOW.

EACH OF THESE WAVES WILL TEMPER WARMING OVER THE WEEKEND...AND SEE
SIMILAR DISCREPANCIES IN LOW LEVEL TEMPERATURES AS DISCUSSED ABOVE
FOR FRIDAY...SO SIMILAR THINKING APPLIES IN KEEPING NORTHEAST TOWARD
MIDDLE RANGE OF GUIDANCE WITH SOUTHWEST ON THE WARMER EDGE OF THE
SPECTRUM...THOUGH NORTHEAST SHOULD SEE A LITTLE BETTER WARMING
POTENTIAL BY SUNDAY...WITH SLIGHTLY ABOVE FREEZING TEMPERATURES
FRIDAY/SATURDAY SLOWLY ERODING THE SNOW COVER.

BY MONDAY/TUESDAY...UPPER FLOW BEGINS TO FLATTEN AND ALLOW WARMER
LOW LEVEL AIR TO MAKE A GREATER SURGE EASTWARD ACROSS THE REGION.
THESE DAYS CONTINUE TO LOOK QUITE WARM WITH MIXY SOUTHWEST FLOW
KEEPING STRATUS POTENTIAL AT BAY...AND 925MB TEMPERATURES WARMING
INTO THE DOUBLE DIGITS MOST AREAS. STRAYED LITTLE FROM PREVIOUS
FORECAST FOR THESE DAYS...WITH LOWER-MID 50S NORTHEAST...AND LOWER
60S ALONG THE MISSOURI VALLEY.

MODELS START TO STRONGLY DIVERGE ON TEMPERATURE TRENDS WEDNESDAY...
WITH ECMWF SHOWING A CONTINUED WARMING TREND WHILE GFS PLOWS A SHARP
COLD FRONT INTO THE REGION. WIDE RANGE OF SOLUTIONS ALSO SEEN AMONG
GFS AND ECMWF ENSEMBLES...WITH EXTREMELY HIGH STANDARD DEVIATIONS
FOR HIGHS TEMPS ON WEDNESDAY...AND A 25-30 DEGREE SPREAD BETWEEN THE
COLDEST AND THE WARMEST MEMBERS IN THE RESPECTIVE ENSEMBLES. WITH
THE LACK OF AGREEMENT...STUCK PRETTY CLOSE TO BROAD BLEND SHOWING A
SLIGHT COOLDOWN FOR NOW. GREATER AGREEMENT ON KEEPING THE LONGER
RANGE PERIOD DRY...THOUGH COLD FRONT SEEN ON THE GFS IS FOLLOWED BY
INCREASING PRECIP CHANCES BEYOND THIS FORECAST PERIOD.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1022 PM CST WED MAR 4 2015

VFR CONDITIONS EXPECTED TO PREVAIL THROUGH THE FORECAST PERIOD.
WITH DEEP ARCTIC AIRMASS IN PLACE...AND WEAK FLOW TO WEAK WARM
ADVECTION AT LOWER LEVELS TOWARD DAYBREAK AT KFSD AND KSUX...WILL
HAVE TO MONITOR FOR DEVELOPMENT OF SOME SHALLOW ICE FOG...PERHAPS
DUE TO MAN MADE INFLUENCE. TOO LOW PROBABILITY EVENT TO MENTION IN
TAFS AT THIS POINT.


&&

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

$$

SHORT TERM...
LONG TERM...JH
AVIATION...CHAPMAN