FXUS63 KFSD 101009
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
407 AM CST THU DEC 10 2009

.DISCUSSION...
THE COOLER TEMPERATURES ARE EXPECTED TO MODERATE SOME OVER THE NEXT 
FEW DAYS AS UPPER LEVEL TROUGH LOOSENS ITS GRIP ACROSS THE AREA AND 
ZONAL FLOW TAKES OVER.  FOR THIS MORNING...WIND CHILLS RUNNING IN 
THE NEIGHBORHOOD OF 20 BELOW. REPORTING STATIONS SUGGESTING WINDS 
RUNNING IN THE 5 TO 10 MPH RANGE...BUT WITH BITTERLY COLD 
TEMPERATURES IN PLACE...A BREATH OF WIND WILL RESULT IN EXTREMELY 
COLD WIND CHILLS.  AS A RESULT...ELECTED TO KEEP WIND CHILL ADVISORY 
IN PLACE THROUGH 16Z AT WHICH TIME WARMING TEMPERATURES SHOULD 
NEGATE INCREASING WINDS.

WEAK SHORTWAVE MOVING OUT OF EASTERN MONTANA INTO NORTHWESTERN SOUTH 
DAKOTA MAY CREATE A FEW FLURRIES ACROSS NORTHERN PORTIONS OF 
FORECAST AREA AS IT SLIPS BY. AS DOME OF COLD AIR SHIFTS EAST...925 
HPA TEMPS ARE EXPECTED TO WARM RANGING -10 TO -15 C. SNOWCOVER 
ACROSS THE AREA WILL MAKE MIXING DIFFICULT...AND AS A RESULT HAVE 
GONE FAIRLY CLOSE TO ISOTHERMAL FROM 925 HPA FOR TODAY. 

WITH DRY AIR MASS...TEMPERATURES WILL ONCE AGAIN FALL BELOW ZERO 
TONIGHT.  WITH LEFT REAR OF STRONG UPPER LEVEL JET HANGING ACROSS 
THE AREA...SHOULD SEE STRONG SUBSIDENCE ALOFT...BUT IN THE LOWER 
LEVELS...WEAK LIFT PERSISTS AND MAY BE ABLE TO GENERATE A FEW 
FLURRIES ACROSS SOUTHWEST MINNESOTA OVERNIGHT. 

MIXING CONDITIONS WILL BE EXTREMELY POOR ON FRIDAY AS FLOW BECOMES 
EXTREMELY LIGHT.  BECAUSE OF THIS...HAVE UNDERCUT GUIDANCE VALUES 
FOR FRIDAY.  

TEMPERATURES SATURDAY INTO SUNDAY WILL REMAIN BELOW AVERAGE. MODELS 
INDICATE A MOIST BOUNDARY LAYER...WITH DRY AIR SITUATED ALOFT.  WITH 
INCREASING MOISTURE IN THE LOWER LEVELS....LOWS WILL LIKELY REMAIN 
ABOVE ZERO. SOUNDING PROFILES ALSO HINT AT POTENTIAL FOR FOG BUT 
LEFT OUT OF FORECAST FOR NOW.  GFS SUGGESTS SHORT WAVE WOULD MIGRATE 
THROUGH THE AREA ON SUNDAY INTO SUNDAY NIGHT. DYNAMICS ARE FAIRLY 
MEAGER WITH THIS DISTURBANCE...AND GEM AND ECMWF FOCUS SHORTWAVE 
ENERGY MUCH FURTHER TO THE SOUTH.  LOWERED POPS TO 15 PERCENT WITH 
THIS FEATURE...BUT WOULD NOT BE SURPRISED IF FUTURE SHIFTS DROP 
MENTION OF PRECIP ALL TOGETHER WITH THIS FEATURE.  BEHIND THIS 
SYSTEM...APPEARS AS THOUGH ANOTHER SHOT OF ARCTIC AIR IS EXPECTED TO 
WORK SOUTH ON MONDAY...A DEVIATION FROM THE 12Z RUNS FROM 
YESTERDAY.  IF THIS IS SHOWN IN THE 12Z RUNS...DAY SHIFT WILL LIKELY 
HAVE TO CUT BACK FORECAST HIGH FOR TUESDAY AND WEDNESDAY. /BT

&&

.AVIATION...
MAINLY VFR CONDITIONS THROUGH THE FRIDAY MORNING. AN OUTSIDE CHANCE 
OVER NORTHERN PORTIONS OF THE AREA FOR A BRIEF MVFR CEILING IN 
SCATTERED FLURRIES FROM LATE MORNING INTO THE AFTERNOON. /08

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
IA...WIND CHILL ADVISORY UNTIL 10 AM CST THURSDAY FOR IAZ001>003-    
     012>014-020>022-031-032.

MN...WIND CHILL ADVISORY UNTIL 10 AM CST THURSDAY FOR                
     MNZ071-072-080-081-089-090-097-098.

NE...WIND CHILL ADVISORY UNTIL 10 AM CST THURSDAY FOR NEZ013-014.

SD...WIND CHILL ADVISORY UNTIL 10 AM CST THURSDAY FOR                
     SDZ038>040-050-052>071.

&&

$$
BT/08