FXUS63 KFSD 052207
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
400 PM CST SAT DEC 5 2009
.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
&&
.AVIATION...
VFR THRU 06Z SUN. MVFR CIGS WILL SPREAD INTO AREAS WEST OF THE JAMES
RIVER AFTER 06Z SUN...AND CONTINUE SOUTHEAST INTO AREAS MAINLY ALONG
AND SOUTH OF INTERSTATE 90 AFTER 15Z. SPOTTY MVFR VSBYS IN -SN PSBL
SOUTH OF INTERSTATE 90 AFTER 15Z AS WELL...MAINLY WEST OF THE JAMES
RIVER VALLEY AND SOUTH OF INTERSTATE 90. BETTER CHANCE OF WIDESPREAD
MVFR-LOCALLY IFR VSBYS IN -SN WILL SPREAD ACROSS AREAS SOUTH OF I-90
INTO NORTHWEST IOWA THROUGH 07/00Z. /JH
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
