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000
FXUS63 KFSD 100458
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1058 PM CST MON DEC 9 2013

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 327 PM CST MON DEC 9 2013

AN UPPER LEVEL WAVE WILL MOVE ACROSS THE AREA TONIGHT...WITH THE
BEST LARGE SCALE FORCING ACROSS THE NORTH. THUS THINKING WE SEE A
PERIOD OF ISOLATED TO SCATTERED SNOW SHOWERS AS THE AREA OF LIFT
COINCIDES PRETTY WELL WITH THE PREFERRED SNOW GROWTH ZONE.
TEMPERATURES MAY DROP A BIT RIGHT AT SUNSET...BUT THEN SHOULD BEGIN
A WARMING TREND AS SOUTHWESTERLY WINDS PICK UP AHEAD OF THE WAVE AND
COLD FRONT. TEMPERATURES WILL EVENTUALLY FALL AGAIN LATER TONIGHT
BEHIND THE FRONT. COULD SEE SOME SOME STRATUS MOVE IN BEHIND THE
FRONT...AND WITH STEEP LOW LEVEL LAPSE RATES AND THE STRATUS IN THE
SNOW GROWTH ZONE...WOULD LIKELY SEE FLURRIES LINGER FOR A WHILE
BEHIND THE FRONT. WINDS WILL CONTINUE TO INCREASE AHEAD AND BEHIND
THE FRONT...TURNING NORTHWESTERLY AND GUSTING INTO THE 30 TO 40 MPH
RANGE...ESPECIALLY NORTH OF INTERSTATE 90. THIS WILL LIKELY CAUSE
SOME REDUCED VISIBILITIES IN ANY SNOW SHOWERS OR FLURRIES. COULD
ALSO SEE SOME BLOWING OF THE SNOW ON THE GROUND...BUT WITH SNOW
DEPTH PRETTY LOW AND NOT THE FLUFFIEST...DO NOT THINK THIS WOULD BE
TOO MUCH OF AN ISSUE. PLUS THE WORST OF THE CONDITIONS SHOULD BE
OVER BY THE MORNING RUSH HOUR AS ANY FLURRIES EXIT AND WINDS BEGIN
TO DIE OFF. THUS WILL NOT ISSUE ANY WINTER WEATHER ADVISORY FOR
BLOWING SNOW AT THIS POINT.

TOMORROW WILL SEE INCREASING CLOUDS FROM WEST TO EAST AS YET ANOTHER
WAVE APPROACHES THE AREA...WITH HIGHS REBOUNDING INTO THE TEENS AND
20S. LOOKS LIKE ANOTHER AREA OF LIGHT SNOW WILL MOVE ACROSS THE AREA
IN THE AFTERNOON OR OVERNIGHT. GEM AND ECMWF ARE FASTER AND THUS
FURTHER NORTH WITH THE SNOW. WITH THE NAM AND GFS SLOWER AND FURTHER
SOUTH. TRENDED THIS FORECAST TOWARDS THE GEM AND ECMWF...AS IT SEEMS
MORE OFTEN THAN NOT WHEN THEY ARE IN ONE CAMP AND THE GFS AND NAM IN
ANOTHER...GOING WITH THE INTERNATIONAL MODELS IS THE WAY TO GO. THE
SREF IS FASTER AS WELL...ADDING A LITTLE CONFIDENCE TO THAT
SOLUTION. THIS WOULD BRING THE LIGHT SNOW INTO THE CWA AROUND OR
SHORTLY AFTER 2 PM AND THEN SPREADING SOUTHEAST. LOOKS LIKE MOST
AREAS WILL PROBABLY SEE AT LEAST SOME LIGHT SNOW. SOME SIGNS OF
FRONTOGENESIS AND INSTABILITY ABOVE THE FRONT...HINTING AT SOME
BANDING POTENTIAL. UNSURE WHERE THIS SETS UP AT THIS POINT...BUT
WHILE MOST AREAS SHOULD SEE AN INCH OR LESS...NOT OUT OF THE
QUESTION WE SEE A FEW ISOLATED AMOUNTS AROUND 2 INCHES OR SO BEFORE
THE SNOW ENDS IN THE EVENING HOURS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 327 PM CST MON DEC 9 2013

A NOT VERY WELL AGREED UPON SYSTEM MOVING QUICKLY THROUGH ON TUESDAY
NIGHT. DID UP POPS JUST A SMIDGE AS MOST LOCATIONS SHOULD SEE A
LITTLE LIGHT SNOW BUT THERE IS A POTENTIAL FOR SOME SLIGHT
ENHANCEMENT OF THIS BAND IN A SMALL LOCATION...JUST A MATTER OF
WHERE. AT THIS TIME IT LOOKS LIKE MAINLY SOUTH OF INTERSTATE 90
AFTER 0Z WEDNESDAY AND THE ACTIVITY SHOULD SHUT DOWN AFTER MIDNIGHT.
BY THEN COLDER AIR WILL DROP SOUTH AND WITH CLEARING SKIES FROM THE
NORTH TEMPERATURES WILL DROP PRETTY QUICKLY IN THE NORTHERN AND
WESTERN PARTS OF THE CWA WHERE CLEAR SKIES AND LIGHTER WINDS ARE
MORE LIKELY. AIMING FOR ABOUT 10 BELOW ZERO IN THESE LOCATIONS TO
AROUND ZERO FROM SUX TO SLB.

WEDNESDAY SHOULD BE PRETTY DARN COLD AGAIN BUT WITH HIGH PRESSURE
MOVING THROUGH WINDS SHOULD NOT BE AS MUCH OF A PROBLEM.
HOWEVER...EVEN AT ABOUT 10 TO 15 MPH WIND CHILL VALUES IN MANY
LOCATIONS WILL DROP TO 25 TO 30 BELOW ZERO LATE TUESDAY NIGHT INTO
WEDNESDAY MORNING. HIGHS WEDNESDAY AFTERNOON WILL REBOUND A BIT AS
THE HIGH PRESSURE SHIFTS SOUTHEAST OF THE AREA...SO 10 TO 15 ABOVE
ZERO SOUTH CENTRAL SD AND AROUND ZERO SOUTHWEST MN.

WEDNESDAY NIGHT INTO THURSDAY WILL SEE A MUCH MILDER AIR MASS
OVERSPREAD THE AREA SO WENT WITH NEARLY STEADY OR RISING
TEMPERATURES WEDNESDAY NIGHT AND HIGHS WELL INTO THE 20S ON
THURSDAY. EVEN LOOKING LIKE A GOOD CHANCE FOR SOME LOWER 30 ALONG
THE MISSOURI RIVER VALLEY.

IN THE OUTER PERIODS (FRIDAY THROUGH MONDAY)....MODELS IN VERY GOOD
AGREEMENT IN SWINGING LOW PRESSURE ALOFT THROUGH SOUTHERN CANADA
INTO THE GREAT LAKES SATURDAY INTO MONDAY WITH A FAIRLY STRONG NORTH
NORTHWEST 120 KNOT JET MAX ON THE BACK SIDE. THIS SHOULD SETTLE
ARCTIC AIR INTO THE REGION FRIDAY NIGHT THROUGH SUNDAY BEFORE WEAK
RIDGING ALOFT ALLOWS FOR A LITTLE WARMING BY MONDAY. WHILE THIS RUN
IS IN GOOD AGREEMENT IT DIFFERS QUITE A BIT FROM PREVIOUS OUTPUT.
HOWEVER...WITH THE MODEL DATA VERY COLD...TEENS TO LOWER 20S BELOW
ZERO AT 925MB SATURDAY AND SUNDAY...AND WITH THE STATISTICAL OUTPUT
SUPPORTING MUCH COLDER CONDITIONS...ESPECIALLY WITH THE ENSEMBLE
NUMBERS COLDER THAN THE MEX NUMBERS WHICH ARE BELOW
CLIMATOLOGY...HAVE DECIDED TO LOWER TEMPERATURES FOR THE WEEKEND BY
10 TO 15 DEGREES. NOT EXPECTING ANY MAJOR SNOW PROBLEMS BUT WILL
HAVE SOME SMALL POPS FOR OCCASIONAL FLURRIES AND SNOW SHOWERS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1045 PM CST MON DEC 9 2013

A FRONT PASSING THROUGH THE AREA TONIGHT MAY BRING SCATTERED FLURRIES
AND LIGHT SNOW TO THE AREA AHEAD OF THE FRONT AND MAINLY NORTH OF
I-90. WINDS WILL TURN NORTHWEST AND INCREASE TO AROUND 20 KT WITH
GUSTS TO 35 KT BEHIND THE FRONT... WITH A BRIEF DROP TO MVFR CEILINGS
WHICH SHOULD LAST A FEW HOURS. SOME FLURRIES IN THE STRATUS BEHIND
THE FRONT ARE POSSIBLE...WHILE THE STRONG WINDS WILL LIKELY REDUCE
VISIBILITIES IN BLOWING SNOW OVERNIGHT. VFR CONDITIONS SHOULD
BECOME WIDESPREAD AGAIN BY 12 TO 15Z - MID MORNING WITH WINDS
BEGINNING TO DIMINISH SOME AS WELL. THE NEXT CLIPPER SYSTEM
APPROACHES THE AREA TUESDAY AFTERNOON AND WILL BRING MID AND HIGH
CEILINGS. MODELS SUGGEST THAT SOME MVFR CEILINGS WILL ALSO BE
POSSIBLE WITH THIS SYSTEM ALONG WITH SCATTERED LIGHT SNOW DEVELOPING
MAINLY AFTER 21Z. BEST POTENTIAL WILL BE THROUGH THE I-90 CORRIDOR
22Z THROUGH 06Z.

&&

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

$$

SHORT TERM...CHENARD
LONG TERM...08
AVIATION...