FXUS63 KFSD 060227
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
827 PM CST SAT DEC 5 2009

.DISCUSSION...
PATCHY STRATUS CAUSING A FEW PROBLEMS ACROSS THE AREA...BUT OTHER 
THAN THIS NO MAJOR CHALLENGES OVERNIGHT. NORTHEAST FLOW OF DRY AIR 
WILL AID IN KEEPING TEMPERATURES FROM TANKING AND LOWS CLOSE TO 10 
ABOVE SEEMS REASONABLE.

INCOMING MODELS CONTINUE TO HINT AT A SNOW EVENT FOR LATE SUNDAY 
AFTERNOON AND SUNDAY NIGHT. DRY AIR FROM THE NORTH LIKELY TO PLAY A 
ROLE IN ACCUMULATIONS HOWEVER WITH DEW POINTS IN THE SINGLE DIGITS 
ADVECTING IN AND NO REAL HINT OF ANY INSTABILITY TO WORK WITH ABOVE 
THE MID LEVEL FRONT. SO...AMOUNTS OF A HALF AN INCH TO AN INCH 
POSSIBLE AS FAR NORTH AS INTERSTATE 90 AND POSSIBLY 2 TO 3 SOUTH OF 
A VERMILLION TO SPENCER IOWA LINE. /08 

&&

.AVIATION...
MVFR CIGS WHICH HAVE DEVELOPED OVER SW MN EARLIER THIS 
EVENING...CONTINUE TO SPREAD SW ACROSS SE SD. THIS TREND SHOULD 
CONTINUE THIS EVENING...BUT MVFR SHOULD NOT BE WIDESPREAD 
TONIGHT...AS CLEAR AREAS OVER CNTRL MN WORK SWRD. OTHERWISE MAINLY 
MID TO HIGH CLOUDS TONIGHT...AND MAYBE A FEW SNOW FLURRIES INTO THE 
JAMES VALLEY AND S CNTRL SD. MVFR STRATUS SHOULD BECOME WIDESPREAD 
SUNDAY AFTERNOON/NIGHT AS SFC LOW PRESSURE MOVES OUT OF THE ROCKIES 
AND ACROSS KS. SNOW WILL SPREAD ACROSS NEBRASKA WITH SOME SNOW 
LIKELY OVER FAR SE SD AND NW IA. LITTLE IF ANY SNOW IS EXPECTED N OF 
I 29 IN SD. 97

&&

.PREV DISCUSSION...
WEAK SURFACE LOW WHICH HAS BEEN DRIFTING THROUGH THE CWA TODAY WILL 
MOVE EAST OF THE AREA THIS EVENING...LEAVING NORTH-NORTHEAST WINDS 
WHICH MAY INCREASE A BIT OVERNIGHT...THOUGH STILL EXPECTED AROUND
10 MPH OR LESS MOST OF THE NIGHT. UPPER LEVEL WAVE DROPPING SOUTH 
THROUGH NORTH DAKOTA AT THIS TIME...WHILE SECOND WAVE TRACKS EAST 
OUT OF THE NORTHERN ROCKIES. A LITTLE SHEAR ZONE BETWEEN THESE TWO 
WAVES WITH WEAK MID LEVEL FRONT SHIFTING SOUTHWARD INTO THE CWA 
OVERNIGHT. DRY LOW-MID LEVEL AIR PERSISTS IN THE NORTHERLY FLOW 
ACROSS AREAS EAST OF JAMES RIVER OVERNIGHT...WHILE DEEPER LOW LEVEL 
MOISTURE NOW OVER WESTERN NORTH DAKOTA IS SHOWN BY MODELS TO WORK 
INTO WESTERN PORTIONS OF THE CWA AFTER 06Z. TEMPERATURES WITHIN THIS 
STRATUS COLD ENOUGH TO SUPPORT A LITTLE FLURRY ACTIVITY...AND HAVE 
ADDED ISOLATED FLURRIES TO FAR WESTERN CWA LATER TONIGHT. THICKENING 
CLOUDS AND INCREASING WINDS SHOULD KEEP TEMPS FROM DROPPING TOO 
QUICKLY...THOUGH HAVE STILL HEDGED ON COLD SIDE OF GUIDANCE FOR MOST 
AREAS.

THINGS BECOME MORE INTERESTING ON SUNDAY AS THE SHORTWAVE OVER THE 
CENTRAL ROCKIES PUSHES OUT ONTO THE PLAINS THROUGH THE DAY. MODELS 
HAVE SLOWED DOWN ONSET OF PRECIPITATION JUST A SMIDGE OVER OUR 
SOUTHWEST IN THE MORNING WITH MIDLEVEL WAA IN ADVANCE OF THE MAIN 
WAVE...BUT WILL SEE IT PICK UP IN INTENSITY ALONG THE MISSOURI RIVER 
CORRIDOR INTO NORTHWESTERN IOWA BY LATE AFTERNOON AS PV ADVECTION 
INCREASES OVER THAT AREA. WILL BE A COLDER DAY WITH HIGHS IN THE 
UPPER TEENS TO LOWER 20S. SHOULD SEE MOST OF THE SNOW OCCUR OVER 
NORTHWESTERN IOWA BETWEEN 21Z TOMORROW INTO 06Z TOMORROW NIGHT WITH 
DEVELOPING 750 MB FRONTOGENESIS...AND PRETTY DECENT LIFT AS 
EVIDENCED BY BROAD AREA OF DIV Q CENTERED FROM EASTERN NEBRASKA INTO 
THE SOUTHERN PORTIONS OF OUR CWA. BY MONDAY MORNING...COULD SEE 2 TO 
3 INCHES OF SNOW ACCUMULATE IN AREAS GENERALLY SOUTH OF VERMILLION 
TO SPENCER...WITH AROUND AN INCH ALONG THE I90 CORRIDOR. COLDER AIR 
WILL CONTINUE TO FILTER IN BEHIND THE SYSTEM...AND TEMPERATURES WILL 
FALL INTO THE SINGLE DIGITS TO AROUND 10 DEGREES ON SUNDAY NIGHT.

THINGS WILL DRY OUT ON MONDAY AS A SURFACE RIDGE PUSHES ACROSS THE 
REGION. MAY KEEP A GOOD BIT OF STRATOCU OVER THE AREA...ESPECIALLY 
IN THE NORTH...AND THIS WITH EXPECTED LIGHT SNOW COVER WILL KEEP 
HIGHS GENERALLY IN THE MID TEENS.

MODELS IN GOOD AGREEMENT WITH NEXT SHORTWAVE TO AFFECT OUR AREA ON 
MONDAY NIGHT AND TUESDAY...ALBEIT THE NAM A LITTLE FARTHER NORTH.  
THE SHORTWAVE WILL TAKE A TRACK SIMILAR TO THE SUNDAY NIGHT 
SYSTEM...WHICH WILL AGAIN BRING THE BEST CHANCE OF PRECIPITATION TO 
OUR SOUTHERN AREAS. MAY SEE A BROADER AREA OF SNOWFALL WITH THIS 
SYSTEM HOWEVER...AND WITH THE DURATION BEING A LITTLE LONGER...INTO 
WEDNESDAY MORNING...COULD SEE HIGHER SNOWFALL AMOUNTS...FROM AROUND 
1 INCH IN OUR NORTHWEST TO POSSIBLY 6 INCHES IN OUR SOUTHEAST. 
TEMPERATURES WILL BE GOING NOWHERE REAL FAST WITH THE SNOW COVER AND 
A COLD AIRMASS IN PLACE ANYWAY...AND HIGHS ON TUESDAY AND WEDNESDAY 
WILL BE HOVERING IN THE LOW TO MID TEENS.

FOR THE END OF NEXT WEEK...MODELS IN FAIRLY DECENT AGREEMENT ON THE 
OVERALL SYNOPTIC FEATURES...WHICH WOULD PUT US IN A NORTHWESTERLY 
UPPER LEVEL FLOW...THOUGH DIFFER SOMEWHAT ON THE SURFACE FEATURES. 
DOES APPEAR TO BE PRIMARILY DRY INTO THE EARLY PART OF NEXT 
WEEKEND...BUT CONTINUING BELOW NORMAL WITH RESPECT TO TEMPERATURES.  
/JM

&&

.FSD WATCHES/WARNINGS/ADVISORIES...

SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

$$