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000
FXUS63 KFSD 132057
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
357 PM CDT THU MAR 13 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 357 PM CDT THU MAR 13 2014

COLD FRONT COMING THROUGH TONIGHT WILL REPLACE THE WARM WEATHER WITH
COOLER BUT STILL ABOVE NORMAL TEMPERATURES FOR FRIDAY. CURRENT
EXPECTATIONS OF ONLY SOME PATCHY MIDDLE CLOUDS STILL LOOK GOOD AND
WILL KEEP THIS FOR TONIGHT. WINDS WILL SHIFT TO NORTHWEST AND PICK
BACK UP A LITTLE AFTER AN EARLY EVENING DROPOFF OF THE SOUTHWEST
BREEZE. TEMPERATURES SHOULD COOL MODESTLY WITH THIS MIXING BREEZE TO
LOWS IN THE 30 TO 35 RANGE BY DAYBREAK FRIDAY.

EXPECT A DECK OF SOLID LOW CLOUDS IN THE COOLER AIR TO STAY JUST
NORTHEAST OF THE AREA FRIDAY...WITH SOME SCATTERED TO BROKEN CLOUD
DEVELOPMENT IN OUR NORTHEASTERN AREA. OTHERWISE SKIES SHOULD STAY
MOSTLY CLEAR. THE HEATING SHOULD HELP THE MIXING FACTOR AND BRING
WINDS UP TO THE BREEZY CATEGORY. PROJECTED BL WINDS SUGGEST WE WILL
NOT BE CLOSE TO A WIND ADVISORY. TEMPERATURES WILL BE COOLER THAN
TODAY BUT SHOULD WARM TO A FEW DEGREES ABOVE GUIDANCE. HIGHS ARE
EXPECTED TO BE IN THE MID 40S NORTHEAST TO THE MID 50S SOUTH.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 357 PM CDT THU MAR 13 2014

DECIDED TO ELIMINATE ANY MENTION OF POPS ACROSS OUR NORTHERN ZONES
FRIDAY NIGHT. THIS IS BECAUSE ALL OF THE LATEST 12Z MODELS SHOW A
BIG LAYER OF DRY AIR BELOW ABOUT 700MB...EVEN IN OUR EXTREME
NORTH. SO EVEN THOUGH OVERALL CLOUD COVER WILL BE ON THE INCREASE...
THINGS SHOULD REMAIN DRY.

THEN ON SATURDAY AND SATURDAY NIGHT...THE MODELS HAVE FINALLY COME
AROUND IN AGREEMENT IN SHOWING A DECENT SHORT WAVE PASSAGE ACROSS
THE HEART OF THE PLAINS. INITIALLY ON SATURDAY...THERE STILL COULD
BE SOME VERY LIGHT PRECIP IN THE FORM OF SNOW OVER SOUTHWEST MN...
RIGHT ALONG A STOUT BAROCLINIC ZONE EXHIBITING STRONG LOW LEVEL
FRONTOGENESIS...AND ALSO PLACED IN THE RIGHT ENTRANCE REGION OF A
JET STREAK OVER THE GREAT LAKES. IT ALSO HELPS THAT THERE IS A BIT
MORE LOW LEVEL MOISTURE ALSO. THEN IN THE AFTERNOON AS THE WAVE
GETS CLOSER...PRECIPITATION SHOULD BEGIN TO FILL IN ACROSS OUR
WESTERN ZONES...WITH CHANCES OF LIGHT RAIN OR SNOW ELSEWHERE
GENERALLY ALONG AND NORTH OF THE I 90 CORRIDOR. A STRIPE OF STRONG
UPPER QG FORCING ELONGATED NORTH TO SOUTH THEN MOVES OVER OUR AREA
SATURDAY NIGHT. AT THE LOWER LEVELS...THERE IS QUITE A SQUEEZE OF
AIR CAUSING CONVERGENCE WITH A LARGE 1035-1040MB HIGH JUST TO OUR
NORTH ALONG THE MN/ONTARIO BORDER...AND LOW PRESSURE THROUGHOUT
THE SOUTHERN PLAINS. THIS SCENARIO SHOULD PUSH THE PRECIP
SOUTHWARD AS THE NIGHT PROGRESSES ACROSS OUR AREA...AND CHANGEOVER
TO COMPLETE SNOW AS COLD AIR ALOFT RUSHES IN FAIRLY RAPIDLY.
SPEAKING OF WHICH...THERE WERE SOME PRETTY BIG DISCREPANCIES IN
THE WARM LAYER ALOFT BETWEEN THE WARMER NAM...AND THE COOLER GFS.
FOR NOW...50/50 BLENDED THE TWO MODELS SATURDAY AFTERNOON AND
NIGHT TO COME UP WITH THE TEMPERATURE ALOFT FORECAST. AT ANY RATE...
WOULD NOT RULE OUT A WIDESPREAD 0.5 TO 1.5 INCHES OF SNOW SATURDAY
NIGHT...WITH MOST OF THE ACCUMULATION ON GRASS.

TEMPERATURES ON SATURDAY STILL LOOK TOO WARM USING MANY OF THE ALL
BLEND FEATURES...WITH THE WEIGHTED MODEL LOOKING THE BEST. JUST
CANNOT IMAGINE WITH A STOUT NORTHEAST WIND THAT AREAS WILL GET AS
WARM AS ADVERTISED AT LEAST NORTH OF I 90...WELL INTO THE 40S
USING MANY OF THE GUIDANCE NUMBERS. SO PREFERRED 30S NORTH OF I 90
ON SATURDAY...WITH 40S SOUTH...EXCEPT 50 TO 55 AT SIOUX CITY.

IN THE EXTENDED...THE MAIN FEATURE TO WATCH FOR IS STILL IN THE
TUESDAY THROUGH WEDNESDAY MORNING TIME FRAME. THE VARIOUS MODELS
CONTINUE TO EXHIBIT A LARGE SPREAD WITH THIS FEATURE. THE GFS IS
FAST WITH THE WAVE PASSAGE...WITH THE UKMET AND ECMWF MUCH SLOWER.
THEREFORE THE GFS WOULD IMPACT OUR FORECAST AREA MAINLY ON
TUESDAY...WITH THE TWO EURO MODELS MORE TUESDAY NIGHT AND EARLY
WEDNESDAY. ALL MODELS ARE SHOWING A DIGGING WAVE AS IT APPROACHES
THE PLAINS...WITH THE UKMET AND ECMWF THEN SHOWING A NEGATIVE TILT
AS IT MOVES EAST OF OUR AREA. THEREFORE SURFACE LOW PRESSURE ALSO
RESPONDS BY DEEPENING RAPIDLY TO THE SOUTH AND SOUTHEAST OF OUR
FORECAST AREA. THIS IS SOMETHING TO WATCH FOR...IN THAT IF THE TWO
EURO SOLUTIONS PAN OUT...WE WOULD GET A DECENT SNOW ACROSS THIS
AREA TUESDAY NIGHT AND WEDNESDAY MORNING. BEING MARCH WITH THE MID
LEVELS PSEUDO ADIABATICALLY UNSTABLE...COUPLED WITH A COLD CONVEYOR
BELT IN THE LOW LEVELS...IT CERTAINLY WOULD BE SNOW. BUT THERE IS
STILL SO MUCH UNCERTAINTY AND VARIANCES BETWEEN THE MODELS THAT
ONE CANNOT GO WITH ANY PARTICULAR SOLUTION YET...SO BLENDING IS
PRUDENT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1227 PM CDT THU MAR 13 2014

VFR EXPECTED OVER THE FORECAST AREA THROUGH 14/18Z. SURFACE GUSTS
FROM THE NORTHWEST OF 25 TO 30 KNOTS POSSIBLE AFTER 14/15Z.


&&

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

$$

SHORT TERM...
LONG TERM...MJ
AVIATION...