FXUS63 KFSD 300257
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
857 PM CST SUN NOV 29 2009

.DISCUSSION...
STRATUS FIELD CONTINUES TO LINGER EARLY THIS EVENING ACRS PARTS OF 
NW IA AND SW MN...BUT CONTINUING TO PULL AWAY EVER SO SLOWLY WITH
SFC RIDGE AXIS FROM NR KDVP TO KSUX LATE EVENING.  AS CLOUDS HAVE 
VACATED WITH WK GRADIENT...TMPS HAVE DROPPED MARKEDLY IN THE EARLY 
EVENING BEYOND EXPECTATIONS VCNTY I 29 CORRIDOR/RIDGE AXIS...AND 
EARLIER UPDATE TO LOWER TMPS INSUFFICIENT AND RECENTLY FOLLOWED UP
WITH A MORE SUBSTANTIAL FALL. HOWEVER...WL GET SOME DECENT WAA 
LATE...AND WITH SFC GRADIENT INCREASING AND MID/HIGH CLDS STREAMING 
IN FROM NW THE LATTER HALF OF THE NIGHT...WL SEE TMPS REVERSE THAT 
TREND STARTING BY SHORTLY AFT 06Z ARND KHON. UPDATED GRIDS/ZFP/PFM
ISSUED. /CHAPMAN

&&

.AVIATION...
VFR THRU 00Z TUES. OCNL CIGS BKN100 08Z-14Z.

&&

.PREV DISCUSSION...
BATCH OF STRATUS EAST OF THE JAMES WILL SLIDE SOUTH AND EAST LEADING 
TO CLEARING SKIES ACROSS THE AREA. SURFACE HIGH PRESSURE OVER SOUTH 
CENTRAL NEBRASKA WILL SLIDE SOUTH OVERNIGHT ALLOWING THE PRESSURE 
GRADIENT TO INCREASE SLIGHTLY. AS THE WESTERLY WINDS INCREASE AND 
CIRRUS CLOUDS INCREASE FROM WEST TO EAST...EXPECT TEMPERATURES TO 
BECOME STEADY IF NOT FLOUNDER A DEGREE OR TWO BEFORE SUNRISE.  HAVE 
RAISED LOWS IN THE WEST...AND KEPT LOWS IN THE EAST AT OR ABOVE 
GUIDANCE ESPECIALLY IN THE EXPOSED LOCATIONS. /BT

OTHERWISE MOST OF THE ACTION FOR THIS NEXT WEEK IS PROBABLY AT THE 
END OF THE EXTENDED PERIOD...MAYBE...IF THE LATEST GFS AND CANADIAN 
GLOBAL HOLD. EARLY IN THE WEEK...UPPER NW FLOW DOMINATE THIS AREA. 
THIS SHOULD PROVIDE CLEAR TO PARTLY CLOUDY SKIES MONDAY AND MONDAY 
NIGHT AND CONTINUING MUCH ABOVE NORMAL TEMPS ON MONDAY...EVEN THOUGH 
MIXING IS POOR. MINS MONDAY NIGHT ARE TRICKY WITH VERY LIGHT RETURN 
FLOW. THEREFORE CONTINUED THE TREND OF BOTTOMING OUT THE LOW LYING 
LOCATIONS AND CONVERSELY...KEEPING THE EXPOSED AREAS QUITE MILD. ON 
TUESDAY...THE NAM AND GFS ARE VERY CLOSE IN TIMING WITH THE SFC 
CDFNT PASSAGE IN OUR AREA. THIS FRONT IS COURTESY OF A STRONG UPPER 
LOW MOVG OUT OF CANADA INTO THE NRN PLAINS. THE DYNAMICS WITH THIS 
SYSTEM ARE POOR THIS FAR SOUTH...SO LEAVING THE FROPA DRY IS 
PRUDENT. FOR NOW...HEDGED TEMPS ON TUE TOWARD THE COOLER MET IN OUR 
NRN FA AND THE WARMER MAV IN OUR SOUTH...HOPING FOR A DECENT THERMAL 
GRADIENT FM N TO S DUE TO THE FRONT. AFTERWORD...BOTH THE NAM AND 
GFS BEGIN TO SHOW AN ONSLAUGHT OF STRATOCU EDGING SWD INTO OUR FAR 
NRN AREAS VERY LATE TUE NIGHT...THEN MOVG SEWD ON WED. BECAUSE OF 
THIS...KEPT HIGHS FOR WED BLO MEX READINGS/    /MJF

THE EXTENDED WED NIGHT THRU SUNDAY IS GETTING MORE INTERESTING. 
FAVORED THE LAST TWO CANADIAN GLOBAL RUNS PLUS THE 12Z GFS. 
INITIALLY...WE ARE DEALING WITH OUR LOW UPPER LOW SITUATED OVER THE 
WRN GRTLKS AND DOWN THE MS VALLEY POURING SOME CHILLY AIR INTO THIS 
AREA WED NIGHT AND THURSDAY. STILL CONCERNED ABOUT STRATOCU BEING A 
PROBLEM WED NIGHT...THEN GRADUALLY PULLING EWD ON THURSDAY. THERE IS 
A DECENT COOL AIR SURGE COMING DOWN WITH THE LAST UPPER LOBE MOVG 
SWD ON THE BACKSIDE OF THE LOW. BUT STILL NOT ENOUGH TO MENTION ANY 
CHCS FOR -SN OR EVEN FLURRIES. AS THIS LOW CONTS ITS SLOW TRACK 
EWD...OUR ATTENTION TURNS TO THE WEST. THE LAST SEVERAL GFS RUNS...
AS WELL AS THE CANADIAN GLOBAL HAVE SHOWN AN UPPER LOW MOVG INTO THE 
PAC NW FRI AND FRI NIGHT...THEN DIVING SWD THRU THE WRN CONUS. I 
IGNORED THIS AT FIRST...BUT IT LOOKS AS THOUGH THERE MAY BE A SFC 
WIND SHIFT THRU THE NRN PLAINS FRI NIGHT AND SATURDAY AS A WEAK S/W 
MOVES EWD ACROSS THE CANADIAN BORDER AHEAD OF THE PAC NW ENERGY. BUT 
IT IS A DRY PASSAGE. THEN THE JET DIVES DOWN THE WRN CONUS 
POTENTIALLY REALLY CARVING OUT A DEEP TROF IN THE SWRN CONUS. THIS 
AGREES WITH THE HPC THINKING...AND COULD SET US UP WITH AN 
OVERRUNNING EVENT ON SUN AND MON AS ARCTIC AIR DRAINS DOWN FM WRN 
CANADA UNDER THE SW FLOW ALOFT. IF THIS SCENARIO STILL HOLDS ON 
MONDAY...I WILL BEGIN TO GREATLY LOWER TEMPS ON SUNDAY...WHICH ARE 
ALREADY A CATEGORY OR TWO BLO HPC AND 00Z GUIDANCE NUMBERS...AND 
CONT THAT TREND INTO MONDAY AND INTRODUCE CHCS FOR SNOW.  /MJF

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

$$