000
FXUS63 KFSD 032155
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
355 PM CST TUE DEC 3 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 350 PM CST TUE DEC 3 2013

RELATIVE QUIET PERIOD FROM LATE MORNING INTO EARLY AFTERNOON IS
STARTING TO CHANGE AS LIFT FORCING SPREADS INTO SOUTH CENTRAL SOUTH
DAKOTA IN ADVANCE OF STRONG JET PUNCHING OUT OF THE CENTRAL ROCKIES.
STRONG FRONTOGENETIC FORCING WILL CONTINUE TO EXPAND ENE ALONG MID
LEVEL BOUNDARY THROUGH THE EVENING...AND SHOULD LEAD TO A QUICK
DEVELOPMENT OF SNOW BAND WITH LIFT AND SNOW GROWTH WELL COLLOCATED
IN PROFILES OF MAIN BAND. SHADED TOWARD A SOMEWHAT COOLER THERMAL
PROFILE OVERALL WITH WET BULB EFFECT AND SUPPORT OF EC/SREF. EVEN
WITH THIS...SHOULD BE WARM ENOUGH ALOFT FOR SOME ALTERNATE TYPES IN
TRANSITION AT ONSET...PROBABLY SLEET AND LIGHT FREEZING RAIN BEFORE
A CHANGE TO SNOW. SOME LIGHT ICE ACCUMULATIONS MENTIONED FOR AREAS
AROUND THE IOWA GREAT LAKES...WHERE LOW LEVEL COOL PUSH WILL BE IN
PROXIMITY TO THE LINGERING WARMER AIR ALOFT.

MAIN CHANGE IN THE FORECAST FROM THE MID TO LATE MORNING UPDATE WAS
TO INTRODUCE A WINTER STORM WARNING TO AREAS GENERALLY NORTH OF A
WINDOM TO SIOUX FALLS TO WAGNER LINE. STILL LOOKING AT A BROAD
BANDING OF 4 TO 6 INCHES SNOWFALL...WITH LOCALLY HEAVIER AMOUNTS.
HARD TO PINPOINT THE EXACT LOCATION OF THE HEAVIER BAND...THE
STRONGER REASON FOR UPGRADING TO THE WARNING WAS COMBINING THE
SNOWFALL WITH GUSTY WINDS OF 25 TO 35 MPH. STRONGEST WINDS WILL
FIRST DEVELOP ACROSS THE WESTERN CWA AFTER MIDNIGHT...AND EXPAND
EASTWARD AS LOW PRESSURE INTENSIFIES TO THE SOUTHEAST LATER TONIGHT
AND WEDNESDAY. WINDS WILL BE SLOW TO INCREASE IN THE FAR EAST WITH
BAGGY GRADIENT NEAR THE INVERTED TROUGH...BUT EVENTUALLY WILL
INCREASE AND CREATE PROBLEMS WITH STRONGER GRADIENT BY LATE DAY IN
SW MN. BLOWING SNOW SHOULD REDUCE VISIBILITIES TO AROUND A HALF MILE
AT TIMES...AND COULD BE BRIEFLY LOWER AT TIMES OF FALLING SNOW.

SNOWFALL NOW LOOKING A BIT MORE APT TO CONTINUE INTO WEDNESDAY
ACROSS THE AREA...BUT WILL SLOW UP FROM SOUTHWEST TO NORTHEAST AS
INVERTED TROUGH PULLS EAST...AND UPPER WAVE WANDERS SLOWLY NORTH OF
THE AREA. TEMPERATURES WILL BE IN STRONG SUPPORT OF ICE PROCESSES
DURING THE DAY...SO PERHAPS EVEN FAVORABLE FOR FLURRIES AFTER
MEASURABLE THREAT WANES.

OTHERWISE...SOME AREAS OF DENSE FOG CONTINUE THIS AFTERNOON ACROSS
SOUTHWEST MINNESOTA...AND SO NOT TO CONFUSE WITH OVERALL WINTER
SCENARIO...HAVE NOT ISSUED A SEPARATE ADVISORY ON THIS FEATURE.
THERE WILL LIKELY BE SOME PATCHES OF FREEZING DRIZZLE INTERSPERSED
WITH FLURRIES UNTIL STRONGER FORCING AND DEEPER MOISTURE SPREADS IN
BY THE EVENING.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 350 PM CST TUE DEC 3 2013

ANY LIGHT SNOW WILL TAPER DOWN TO FLURRIES ON WEDNESDAY NIGHT AS THE
SYSTEM PULLS AWAY AND FORCING IS LOST. CONFINED ANY BLOWING SNOW IN
THE EVENING TO AREAS WHICH COULD ACTUALLY RECEIVE AT LEAST A TENTH
OF AN INCH OF SNOW...THOUGH WINDS WILL ONLY MARGINALLY DIMINISH
OVERNIGHT WITH A TIGHT GRADIENT REMAINING ACROSS THE REGION...SO
COULD SEE PATCHY BLOWING SNOW OVER OTHER AREAS. EVEN WITH COLD AIR
ADVECTION CONTINUING...TEMPERATURES WILL REMAIN SOMEWHAT IN CHECK ON
WEDNESDAY NIGHT WITH ABUNDANT CLOUD COVER AND THE ABOVE MENTIONED
WINDS...THOUGH READINGS WILL STILL DROP TO AROUND ZERO BY VERY EARLY
THURSDAY MORNING. WIND CHILLS OVERNIGHT WILL JUST MEET WIND CHILL
CRITERIA IN SOME AREAS...AND MAY HAVE TO DEAL WITH THAT AT SOME
POINT IN REGARD TO HEADLINES...BUT WITH THE CURRENT HEADLINES OUT
DID NOT WANT TO CONFUSE THE MATTER.

SURFACE HIGH PRESSURE BEGINS TO BUILD INTO THE REGION ON
THURSDAY...AND IT WILL REMAIN BREEZY IN A COLD AIR ADVECTION
REGIME...ALTHOUGH WINDS WILL SLOWLY TAPERING DOWN DURING THE DAY AS
THE GRADIENT RELAXES A BIT. NOT SURE HOW QUICKLY CLOUDS WILL
DECREASE DURING THE DAY...WITH BOTH THE NAM AND GFS HINTING AT
STRATUS LINGERING THROUGH THE DAY. IN LIGHT OF THAT AND WITH SNOW
COVER ACROSS THE AREA WENT ON THE LOW SIDE OF GUIDANCE WITH HIGHS
ONLY IN THE SINGLE DIGITS AND TEENS. BY THURSDAY NIGHT IT DOES LOOK
LIKE THERE SHOULD BE MORE CLEARING...THOUGH WINDS WILL NOT
COMPLETELY DROP OFF...REMAINING CLOSE TO 10 KTS. BECAUSE OF
THAT...AGAIN THINK THAT TEMPERATURES WILL NOT COMPLETELY BOTTOM
OUT...THOUGH WENT ON THE LOW SIDE OF GUIDANCE WITH LOWS FROM NEAR 10
BELOW IN THE NORTH TO NEAR ZERO IN THE FAR SOUTHEAST. IF WINDS WOULD
BECOME CALM THEN IT WILL BE COLDER THAN CURRENTLY FORECASTED.

BY FRIDAY...925 MB TEMPERATURES ARE PROGGED TO BE WELL INTO THE
NEGATIVE UPPER TEENS TO NEGATIVE LOWER 20S C...AND WENT BELOW
GUIDANCE WITH HIGHS IN THE SINGLE DIGITS. FRIDAY NIGHT IS SETTING UP
TO BE THE COLDEST NIGHT OF THE NEXT FEW AS THE HIGH PRESSURE AXIS
MOVES OVERHEAD AND WINDS BECOME NEARLY CALM. THE ONLY FLY IN THE
OINTMENT WILL BE THE POSSIBILITY OF INCREASING MID AND HIGH
CLOUDS...BUT WENT BELOW ALL BLEND GUIDANCE...AND AM STILL PROBABLY
TOO WARM AS MODEL RUNS ARE COLDER. AT THIS POINT...HAVE LOWS IN THE
MID TEENS BELOW ZERO TO THE SINGLE DIGITS BELOW.

IN THE EXTENDED...SATURDAY THROUGH TUESDAY...THE COLD AIR LOOKS TO
BE LOCKED IN THROUGH THE PERIOD. MODELS IN FAIRLY DECENT AGREEMENT
ON BRINGING A CHANCE OF SNOW TO THE AREA SOMETIME IN THE SUNDAY TIME
FRAME...AS A NORTHERN STREAM UPPER LEVEL TROUGH BEGINS TO DROP INTO
THE NORTHERN PLAINS AND A SOUTHERN STREAM WAVE EJECTS OUT OF THE
DESERT SOUTHWEST. A REINFORCING SHOT OF COLD AIR DROPS INTO THE
REGION FOR THE BEGINNING OF NEXT WEEK WITH THE PASSAGE OF THIS
SYSTEM...AND MODELS HINTING THAT IT COULD BE EVEN COLDER THAN THE
UPCOMING COLD SPELL...THOUGH WILL HAVE TO WATCH AS IT IS STILL
PRETTY FAR OUT. IN ANY EVENT...STAYED ON THE LOW SIDE OF GUIDANCE
THROUGH THE PERIOD WITH EXPECTED SNOW COVER. THIS WILL PLAY OUT TO
HIGHS SINGLE DIGITS AND TEENS AND LOWS A FEW DEGREES EITHER SIDE OF
ZERO.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1138 AM CST TUE DEC 3 2013

VERY COMPLEX WEATHER PATTERN SETTING UP ACROSS THE AREA THROUGH THE
TAF PERIOD WITH LOW CEILINGS AND VISIBILITY EXPECTED. CEILINGS WILL
REMAIN AROUND 1200 FEET OR LESS. A BAND OF SNOW WILL MOVE INTO SOUTH
CENTRAL SD IN THE NEXT FEW HOURS AND SLOWLY SPREAD EAST NORTHEASTWARD
TOWARDS THE I29 CORRIDOR BY AROUND 00Z...CONTINUING INTO SW MINNESOTA
THROUGH 03Z. LOCALLY MODERATE SNOWFALL IS POSSIBLE IN THE BAND AND
MAY DROP VISIBILITY AS LOW AS 1/2 SM AT TIMES. THE EXACT LOCATION OF
THE HEAVIER BAND IS STILL SOMEWHAT UNCERTAIN...BUT THE BEST POTENTIAL
RIGHT NOW APPEARS TO BE FROM SOUTH CENTRAL SD INTO THE KFSD AREA INTO
THE WINDOM/MARSHALL AREA. FAR SOUTHEAST SOUTH DAKOTA AND NORTHWEST
IOWA WILL SEE LESSER CHANCES OF PRECIPITATION WHILE WARMER
TEMPERATURES IN THIS AREA WILL ALLOW PRECIPITATION TO FALL INITIALLY
AS RAIN OR FREEZING RAIN BEFORE CHANGING TO SNOW FROM WEST TO EAST
OVERNIGHT. ADDITIONALLY...BREEZY NORTHERLY WINDS DEVELOPING THIS
EVENING AND TONIGHT WILL FURTHER REDUCE VISIBILITY BY CREATING AREAS
OF BLOWING AND DRIFTING AT TIMES. CANNOT RULE OUT OCCASIONAL
REDUCTIONS TO 1/4SM OR LESS IN SNOW BANDING AND WIND. AFTER
09Z...CONDITIONS WILL IMPROVE GRADUALLY FROM SOUTHWEST TO NORTHEAST
INTO THE END OF THE TAF PERIOD 18Z/WEDNESDAY...BUT SCATTERED LIGHT
SNOWFALL AND GUSTY WINDS WILL PERSIST.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     SDZ068-069.

     WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     SDZ038>040-050-052>060-063>065.

     WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     SDZ061-062-066-067.

MN...WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     MNZ071-072-080-081-097.

     WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     MNZ098.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     MNZ089-090.

IA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
     IAZ001-002.

NE...NONE.

&&

$$

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