FXUS63 KFSD 252144
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
345 PM CST FRI DEC 25 2009

.DISCUSSION...
CHRISTMAS STORM CONTINUES TO ROLL ALONG. BLIZZARD AND WINTER STORM 
WARNINGS CONTINUE THROUGH NOON SATURDAY. RADAR RETURNS INDICATING 
INSTABILITY AND SEEING SOME CONVECTIVE TYPE SNOWS FALLING OVER THE 
AREA. COLD POCKET OF AIR WITH THE UPPER LEVEL LOW IS INCREASING MID 
LEVEL LAPSE RATES...CONTRIBUTING TO CONVECTIVE POTENTIAL THIS 
AFTERNOON. BAND OF CONVECTIVE LIKE SNOW WILL SHIFT WEST ACROSS MUCH 
OF THE CWA THE REMAINDER OF THIS AFTERNOON. SNOW RATES IN EXCESS OF 
ONCE INCH PER HOUR ARE POSSIBLE AT TIMES. ONCE THIS INSTABILITY IS 
RELEASED...SNOWFALL RATES WILL DECREASE QUITE A BIT BY THIS EVENING. 
TROUGH OF WARM AIR ALOFT WILL REMAIN IN PLACE TONIGHT INTO 
TOMORROW...ALLOWING FOR LIGHT TO MODERATE SNOW TO CONTINUE. 

WINDS WILL REMAIN A PROBLEM TONIGHT...ESPECIALLY THROUGH THE 
MISSOURI AND JAMES VALLEYS WHERE 30 TO 40 MPH WILL BE THE RULE. 
VISIBILITIES IN RURAL AREAS WILL REMAIN NEAR ZERO INTO SAT MORNING. 
FARTHER E...CURRENT WIND SPEED OF GENERALLY 10 TO 20 MPH ARE 
OCCURRING OVER MUCH OF NW IA AND SW MN THIS AFTERNOON. WINDS ARE 
EXPECTED TO AGAIN INCREASE INCREASE TONIGHT AS ARCTIC MAKES AN EWRD 
PUSH. ONE INTERESTING NOTE...ALSO SEEING COLD AIR WRAPPING ALL THE 
WAY AROUND THE LOW PRESSURE CENTER...WITH COLD AIR ADVECTING W INTO 
NW IA FROM ERN IA.

WRAPAROUND SNOWSTORM WEAKENS FROM SATURDAY THROUGH SATURDAY NIGHT
AS SYSTEM GETS CUT OFF FROM ITS BAROCLINICITY AND MOISTURE INFLOW...
AND CAN BASICALLY CALL IT PERIODS OF LIGHT SNOW WITH AREAS OF 
BLOWING SNOW SAT...BECOMING SCATTERED AREAS AS THE SYSTEM PULLS EAST 
SAT NGT. 1 TO 3 INCHES ADDITIONAL SNOWFALL EXPCD...MAINLY IN THE 
NWRN CWA WHERE BEST WRAPAROUND BAND LINGERS THRU SAT MRNG. LEFTOVER 
CLOUDINESS AND NLY WIND FLOW SHOULD KEEP TEMPS FROM DROPPING TOO 
MUCH SAT NGT. SUBSIDENCE SHOULD BREAK UP CLOUDS AND GRADIENT WEAKENS 
BY SUN NGT...PERMITTING TEMPS TO DROP BLO GUID WITH FRESH SNOW 
COVER...ESP IN THE WRN CWA WITH WEAKEST GRADIENT. THEN SNOW COVER 
ALBEDO WILL LIKELY KEEP TEMPS BELOW GUID FOR REST OF FCST...ESP WITH 
EXPCD RESURGENCE OF COLDER AIR FROM NORTH BY THURS. SOME WARMING 
PSBL NEAR MISSOURI VALLEY FRI AS WMFNT APPROACHES. DID ADD SLGT CHC
LGT SNW MAINLY SERN CWA FOR TUE NGT INTO WED WITH WEAK SHORT WAVE...
BUT SURE DOES NOT LOOK LIKE MUCH. /RYRHOLM

&&

.AVIATION...
WEATHER CONDITIONS TODAY AND TONIGHT WILL BE HAZARDOUS AS A WINTER 
STORM CONTINUES ACROSS THE AREA. WIDESPREAD LIFR TO IFR CONDS WL 
OCCUR WITH SN AND BLSN. NW WINDS WL BE STRONG...AVERAGING 25 TO 45 
MPH ALONG AND W OF I 29. SOMEWHAT LIGHTER WINDS WILL BE FOUND IN SW 
MN AND NW IA...BUT PERIODS OF SNOW WILL GREATLY REDUCE VISIBILITIES 
IN THOSE AREAS. IN THE BLIZZARD WARNING AREA WHICH BASICALLY 
ENCOMPASSES THE I 29 CORRIDOR AND POINTS WWD...VLIFR VIS WL OCCUR AT 
TIMES. PILOTS NEED TO STAY ABREAST OF AIRPORT CLOSURES IN THIS AREA. 
AT THIS TIME...FSD AIRPORT IS EXPECTED TO BE CLOSED UNTIL 10 AM SAT. 
MJF/97

&&

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
IA...WINTER STORM WARNING UNTIL NOON CST SATURDAY FOR IAZ001>003-
     012>014-020>022-031-032.

MN...WINTER STORM WARNING UNTIL NOON CST SATURDAY FOR MNZ071-072-080-
     081-089-090-097-098.

NE...WINTER STORM WARNING UNTIL MIDNIGHT CST TONIGHT FOR NEZ013-014.

     BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST SATURDAY FOR 
     NEZ013-014.

SD...WINTER STORM WARNING UNTIL MIDNIGHT CST TONIGHT FOR SDZ038>040-
     050-052>071.

     BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO NOON CST SATURDAY FOR 
     SDZ038>040-050-052>071.

&&

$$