FXUS63 KFSD 071000
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
400 AM CST SUN DEC 6 2009
.DISCUSSION...
LIGHT SNOW ACROSS ERN CWA TAPERING OFF AS DRIER AIR IN THE MID
LEVELS WORKS IN FM THE SW. SO FLURRIES SHUD END THIS MORNING. ALSO
DRY AIR ALOFT IS WORKING DOWN TO SFC AND CLEARING SKIES OUT ACRS FAR
SWRN CWA. MODELS DO PICK PU ON THE DRIER AIR WORKING IN FM ALOFT AND
WUD EXPECT SOME SUN ACRS CWA TODAY WITH THE SCOURING OUT OF THE LOW
CLOUDS. WL NOT WARM MUCH TODAY WITH THE COLD H925 TEMPS. WL HAVE A
HARD TIME GETTING OUT OF TEENS FOR HIGHS.
FOCUS SHIFTS TO LATER TONIGHT INTO TUES NIGHT AS FAIRLY POTENT S/W
MOVES QUICKLY ACRS THE CENTRL PLAINS ON TUES. WITH VERY COLD AIR IN
THE LOW LEVELS AND DECENT MID LEVEL FNTLGEN DEVELOPING ACRS SRN CWA
LATE TONIGHT AND TUES SHUD SEE A WDPRD AREA OF SNOW DEVELOPING ACRS
FAR SRN CWA TOWARDS 12Z TUES AND EXPANDING NWD ACRS CWA ON TUES.
DECENT ISENT LIFT...ESCPEC ACRS SERN CWA TUES AFTN AND NIGHT. WL BE
VERY EFFICIENT PRODUCING SNOW EVEN WITH STRONGER LOW LEVEL DYNAMICS
WELL S OF CWA. SNOW RATIO WL BE IN THE 15 TO 20:1 RATIO WITH DEEP
DENDRITIC LAYER. HEAVIEST SNOW SHUD BE ACRS SERN CWA TUES AFTN AND
NIGHT AND WUD NOT BE SUPRISED TO SEE 6 TO 8 INCHES OF SNOW SE OF A
SUX-SPW LINE. FURTHER NW WL TAPER OFF TO 2 TO 4 INCHES FM
YKN-FSD-MWM LINE. FURTHER NW OF THAT AREA...ISENT LIFT AND FNTGEN
MUCH WEAKER AND MORE OF A BROAD AREA OF LIGHT SNOW EXPECTED. GFS HAS
IT'S TYPICAL HIGH BIAS QPF WITH THIS STORM..SO CAN CUT THAT IN HALF.
STILL WUD YIELD A QUARTER TO A THIRD OF AN INCH ACRS SERN HALF OF
CWA...WHICH IS STILL ENUF TO PRODUCE FCST SNOW AMOUNTS DUE THE HIGH
SNOW RATIO. SO WL KEEP WS WATCH GOING IN CURRENT AREA AND ISSUE
WINTER WX ADVY ALONG A YKN-FSD-MWM LINE TUES AND TUES NIGHT. AS SFC
LOW DEEPENS ACRS CNTRL PLAINS ON TUES...LOW LEVEL NELY FLOW WL
INCREASE TUES AFTN AND INCREASE AND BECOME QUITE WINDY OUT OF N TUES
NITE. WITH SUCH A HIGH SNOW RATIO...WL SEE QUITE A BIT OF BLOWING
SNOW ACRS ERN CWA. THE WORST OF THE WX CONDITIONS WL BE FM MID TO
LATE TUES AFTN THRU TUES NIGHT. HWVR...WITH SNOW STARTING IN THE
MORN...SEE TO REASON TO CHANGE START TIME OF HEADLINES...BUT LATER
SHIFTS CAN FINE TUNE START TIMES AS MODELS GET BETTER TIMING ON THE
WORST CONDITIONS. IN ADDITION TO THE WIND AND SNOW...STGER CAA WL
DEVELOP TUES NITE AND WILL SEE WINDS CHILLS DROPPING TO 5 BELOW TO
20 BELOW DURING THE NIGHT. THESE GUSTY WNDS WL PERSIST INTO
WED..EPEC ERN CWA WITH BULK OF SNOW ENDING BY 15Z ACRS FAR ERN CWA.
WL HAVE A HARD TIME RISING OUT OF THE SINGLE DIGITS FOR HIGHS ON
WED. WL REMAIN QUITE COLD THU AND FRI. WL SEE SUB ZERO LOWS THU MORN
ACRS MOST OF CWA. WNDS AND CLOUDS PBLY WL KEEP TEMPS FM TANKING TOO
MUCH...BUT WL NEED TO WATCH THIS AS MODELS TEND TO UNDER FCST THE
STRENGTH OF THE ARCTIC AIR. DID LOWER LOWS A FEW DEG...BUT MAY NOT
BE COLD ENUF AND IF CONDITIONS ARE JUST RIGHT...CUD SEE LOWS
APPROACHING -10 ACRS PORTIONS OF THE NRN CWA BY THU MORN.
WL LEAVE THU AND FRI DRY FOR NOW...BUT CAN NOT RULE OUT A FEW
FLURRIES THU AND FRI AS NW FLOW ALOFT PRODUCES A FEW WEAK S/W'S.
MOISTURE IS LACKING SO WL BE HARD TO PRODUCE MUCH IF ANYTHING.
LOOKS LIKE TEMPS WL REMAIN WELL BLO NORM THRU NEXT WEEKEND WITH HIGH
TEMPS PBLY NOT REACHING 20.
&&
.AVIATION...
MVFR THIS MORN WL BECOME VFR DURING THE DAY FM THE SW. MVFR
CONDITIONS EXPECTED TO REDEVELOP TONIGHT WITH LIGHT SNOW SPREADING N
TO THE MO RVR BY 12Z TUES.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
IA...WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO 6 AM CST WEDNESDAY
FOR IAZ001-002.
WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR IAZ003-012>014-020>022-031-032.
MN...WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO 6 AM CST WEDNESDAY
FOR MNZ080-081-089-090-097-098.
NE...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR NEZ013-014.
SD...WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO 6 AM CST WEDNESDAY
FOR SDZ056-061-062-065>069.
WINTER STORM WATCH FROM TUESDAY MORNING THROUGH LATE TUESDAY
NIGHT FOR SDZ070-071.
&&
$$
