FXUS63 KFSD 261051
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
450 AM CST SAT DEC 26 2009

.DISCUSSION...
DECIDED TO ALTER THE WINTER WX HEADLINES SOME. CURRENTLY...SFC 
ANALYSIS SHOWS A DOUBLE BARRELED LOW STRUCTURE...WITH ONE LOW PRES 
CENTER NEAR WINDOM AND WORTHINGTON MN...AND THE OTHER STRONGER LOW 
IN SWRN IA. THE SWRN IA LOW WL LIKELY SHUNT OFF TO THE EAST ACROSS 
SRN IA TODAY...WHILE THE SW MN LOW PIVOTS THRU NW IA AND WEAKENS 
WHILE IT DOES SO. WHAT DOES ALL THIS MEAN...WINDS WL STAY PRETTY 
LIGHT TODAY IN AREAS FROM AROUND WORTHINGTON AND WINDOM MN...TO MUCH 
OF NW IA. THEREFORE OPTED TO CHANGE THE WINTER STORM WARNING FOR SW 
MN AND NW IA TO A WINTER WX ADVY...AND KEPT IT RUNNING THRU NOON. 
ELSEWHERE...CHANGED THE BLIZZARD WARNING TO A WINTER WX ADVY FROM 
SIOUX FALLS...DOWN THE BIG SIOUX RIVER CORRIDOR TO SIOUX CITY. IN 
THESE AREAS...WINDS WL BE...OR BECOME A BIT BREEZY TODAY AT 15 TO 25 
MPH. BUT WELL LESS THAN BLIZZARD WARNING CRITERIA AND BETTER 
VISIBILITIES EXPECTED. HOWEVER DUE TO THE BRISK WIND THIS 
AFTERNOON...EXTENDED THE WINTER WX ADVY TO 6 PM. ALONG AND WEST OF A 
YANKTON TO BROOKINGS SD LINE...THAT AREA IS STILL EXPERIECING A 
TIGHT SFC PRS GRADIENT BEHIND THE LOWS WITH STRONGER WINDS ALOFT. 
THEREFORE THEY WL BE PRETTY WINDY THIS MORNING...WITH WINDS NOTCHING 
DOWN A BIT THIS AFTERNOON. THEREFORE WE WL KEEP THE BLIZZARD WARNING 
GOING IN THOSE AREAS UNTIL NOON...THEN A WINTER WX ADVY UNTIL 6 PM 
FOR AREAS OF BLSN. 

OTHERWISE...PV ANAMOLIES CONT TO ROTATE AROUND THE BACKSIDE OF THE 
UPPER LOW TODAY...COUPLED WITH WEAKENING ISENTROPIC LIFT. SO 
RESIDUAL -SN WL STILL OCCUR...LIKELY MORE INTERMITTENT THEN 
YESTERDAY...WITH ADDITIONAL ACCUMULATIONS LESS THAN 2 INCHES BETWEEN 
6 AM AND 6 PM TODAY. OUR FAR ERN CWFA MAY ONLY SEE AREAS OF -SN AS A 
MODESTLY DRIER AIRMASS ALOFT ADVECTS INTO THAT AREA THRU THE MID 
LEVELS. REMEMBER...IN ANY SNOW BANDS TODAY...VIS WL BE REDUCED IN 
THE OPEN COUNTRY...ESP ALONG AND W OF I 29 WHERE THE WIND WL STAY 
UP. THIS WL MAKE TRAVEL DIFFICULT CONTINUING TODAY. 

ANOTHER INTERESTING ITEM TODAY IS THE TEMPERATURES. REALLY NEAT WARM 
AIR RIBBON HAS WRAPPED SOUTHWESTWARD INTO MUCH OF THE I 29 CORRIDOR
FROM CENTRAL MN. KIND OF LIKE A TROWAL AT THE SFC IF THERE IS SUCH 
AN ANIMAL. BUT IT IS CERTAINLY A STRIPE OF WARM AIR WHICH HAS 
WRAPPED BACK IN BEHIND THE LOW. THEREFORE MILD MORNING MAX TEMPS WL 
OCCUR IN THIS RIBBON BEFORE SLOWLY FALLING. ELSEWHERE...TEMPS WL 
LIKELY STAY RATHER STEADY.

TONIGHT...THE LAST OF THE PV AND -DIV Q SURGES ROTATE DOWN THRU THIS 
FA...ESP IN THE EVENING AS THE UPPER LOW CONTS TO MOVE OFF TO THE 
EAST. THEREFORE BELIEVE THAT -SN IS STILL LIKELY IN THE EVENING...
BECOMING A BIT MORE SPOTTY AFTER MIDNIGHT. PCPN DOES LOOK PRETTY 
LIGHT THOUGH...WITH ADDITIONAL AMOUNTS PROBABLY STAYING LESS THAN AN 
INCH EVERYWHERE. DID NOT NEED TO ALTER LOWS TOO MUCH AT ALL WITH 
H925 TEMPS STAYING IN THE MID TEENS. 

FINALLY ON SUNDAY...THE CWFA SHOULD BE REDUCED TO FLURRIES AS UPPER 
CYCLONIC FLOW STILL LINGERS WITH THE UPPER LOW NEAR CHICAGO. HOWEVER 
THE FORCING HAS LARGELY ENDED. WITH A STOUT NW SFC WIND CONTINUING...
MAX TEMPS WL LIKELY NOT BE THAT CHILLY FOR A POST SNOW STORM...AND 
TOOK READINGS ISOTHERMAL FM H925. OTHERWISE EARLY NEXT WEEK...UPPER 
RIDGING FINALLY TAKES OVER BRINGING QUIET WX. RETURN FLOW AND A LACK 
OF ARCTIC AIR PLUNGE SHOULD KEEP OUR TEMPS FM BOTTOMING OUT THAT BAD 
IN THE EARLY MORNING. LITTLE S/W STILL MOVES THRU THIS AREA TUE 
NIGHT AND WED AFFECTING OUR ERN FA...BUT DOES NOT LOOK TO BE ANY BIG 
DEAL AT ALL. 

THANKS TO ALL INCLUDING SURROUNDING WFO'S...MEDIA AND ROAD 
DEPARTMENTS FOR HELPING TO MAKE THIS PROLONGED EVENT BEARABLE. I 
BELIEVE IT WAS WELL FORECAST AHEAD OF TIME AND EVERYONE GOT THE WORD 
OUT WHICH KEPT HOLIDAY TRAVEL TO A MINIMUM. DECADES AGO WITH LESS 
MASS MEDIA ANNOUNCING WARNINGS AND WORSE MODELS...THIS COULD HAVE 
BEEN A DISASTER WITH A LOT OF PEOPLE TRAVELING AROUND.    /MJF

&&

.AVIATION...

WEATHER CONDITIONS EARLY THIS MORNING 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 40 
MPH W OF I 29. LIGHTER WINDS WILL BE FOUND IN SW MN AND NW IA...BUT 
PERIODS OF SNOW WILL GREATLY REDUCE VISIBILITIES IN THOSE AREAS. 
THESE SNOW SHOWERS WILL BECOME LESS NUMEROUS...ESPECIALLY AFTER 00Z 
ON THE 27TH AS THE STORM SYSTEM WEAKENS AND SHIFTS EAST. ALONG 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.   /BT

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
IA...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR IAZ001-
     012-020-031.

     WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR IAZ002-003-013-
     014-021-022-032.

MN...WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR MNZ071-072-080-
     081-089-090-097-098.

NE...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR NEZ013-
     014.

SD...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR SDZ056-
     062-067-070-071.

     BLIZZARD WARNING UNTIL NOON CST TODAY FOR                       
     SDZ038>040-050-052>055-057>061-063>066-068-069.

     WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 PM CST THIS        
     EVENING FOR SDZ038>040-050-052>055-057>061-063>066-068-069.

&&

$$