FXUS63 KFSD 010307
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
905 PM CST MON NOV 30 2009

.DISCUSSION...
CURRENT FCST ON TRACK. CLR SKIES AND LIGHT WINDS ALLOWING TEMPS TO 
FALL FAIRLY QUICKLY THIS EVE. GRIDS HAVE THIS COVERED WELL AND NO 
REASON TO UPDATE FCST. 

&&

.AVIATION...
VFR CONDITIONS EXPECTED THROUGH 00Z WED DEC 2.  LIGHT WEST TO 
SOUTHWEST FLOW WILL TRANSITION TO SOUTHERLY OVERNIGHT. COLD FRONT 
WILL MOVE THROUGH THE AREA AFFECTING KHON AROUND 15Z...KFSD AROUND 
17Z AND KSUX AROUND 19Z. NORTHWEST WINDS WILL INCREASE BEHIND THE 
FRONT AND BECOME GUSTY UP TO 25KTS. THE GUSTS WILL GRADUALLY 
DECREASE FROM WEST TO EAST AFTER 22Z ON DEC 1.  

&&

.PREVIOUS DISCUSSION...
DRY AIR AT LO AND MID LVLS SHUD EXTEND TO HIR LEVELS TNGT AS RIDGING 
AHD OF TUE CDFNT PASSES OVER AREA...SO SKIES SHUD BE CLR/MOCLR THO 
THE VERY END OF THE NGT CUD SEE THE BEGINNINGS OF A FEW MID AND 
INCRNG HI CLDS FAR N/NW. DECOUPLING WILL ALLOW FOR FAIRLY LGT 
WNDS...GUIDNCE AS USUAL HOLDS SFC BREEZE UP A BIT TOO MUCH...SO 
TEMPS SHUD DROP CLOSE TO OR BLO GUIDNCE LOWS.   /WILLIAMS

AS ELUDED TO ABOVE...LEADING EDGE OF SIGNIFICANT CDFNT MOVES ACROSS 
THE FSD FA ON TUE...WITH ONLY VERY MINOR DIFFERENCES ON TIMING 
BETWEEN THE NAM AND GFS. WINDS INCREASE TO THE WINDY CATEGORY IN OUR 
WRN FA BEHIND THE FRONT TUE AFTERNOON...BUT SPEEDS ALOFT STILL 
SUGGEST THAT IT WL REMAIN BLO ADVY CRITERIA. MAX TEMPS ARE ALSO A 
LITTLE TRICKY. CAA IS PRETTY STRONG BEHIND THE FRONT WEST OF I 29 FM 
TUE MIDDAY ON...BUT THAT SHOULD BE TEMPERED BY DECENT MIXING. 
CONVERSELY IN NW IA...THEY ARE AHEAD OF THE FRONT MUCH OF THE DAY 
WITH A SW SFC WIND. THEREFORE HEDGED MAX TEMPS TOWARD THE COOLER MET 
GUIDANCE IN OUR N AND W...AND TOWARD THE WARMER MAV GUIDANCE IN NW 
IA. ATTM...THE MODELS ARE STILL NOT SHOWING ANY STRATOCU COMING DOWN 
BEHIND THE FRONT ON TUE...AND INDEED THERE IS VERY LITTLE OF IT 
UPSTREAM IN S CENTRAL CANADA RIGHT NOW. BUT THEY DO CONT TO SHOW A 
STRIPE OF MID AND HIGH CLOUDS NEAR THE ADVANCING UPPER TROF. 
HOPEFULLY THAT WL NOT BE ENUF TO COOL MAX READINGS IN NW IA.

THEN TUE NIGHT AND WED...THE UPPER LOW ENTRENCHES ITSELF ACROSS THE 
NRN PLAINS...PARTIALLY DUE TO A STRONG JET DIVING DOWN THE BACKSIDE 
OF IT ACROSS THE RCKYS. THIS LEAVES CHILLY AIR IN PLACE AND BREEZY 
CONDITIONS. BOTH THE NAM AND GFS BEGIN TO SHOW THE LEADING EDGE OF 
THE STRATOCU MOVG INTO OUR NW FA AROUND HURON WED MORNING...THEN 
CONTINUING TO HEAD SEWD FM THERE ACROSS THIS ENTIRE AREA. FOR 
TEMPS...KEPT THEM SOMEWHAT MODERATED TUE NIGHT DUE TO THE WIND... 
WITH LITTLE IN THE WAY OF A RISE ON WED WITH THE ADVANCING LOWER 
CLOUDS. 

ON WED NIGHT AND THURSDAY...THE CENTER OF THE UPPER LOW BEGINS TO 
NUDGE EWD INTO THE WRN GRTLKS WHICH IS CONSISTENT WITH EARLIER MODEL 
RUNS. ANOTHER CONSISTENT FEATURE IS ANOTHER SURGE OF CAA COMING DOWN 
BOTH NEAR THE SFC AND MID LEVELS WHICH SHOULD STRAIN OUT SOME 
FLURRIES WITH ABUNDANT STATUS. KIND OF THE SAME STORY ON TEMPS...BUT 
A COUPLE OF CATEGORIES COOLER COMPARED TO TUE NIGHT AND WED WITH AN 
OVERALL COLDER AIRMASS AND CLOUDS. NW WINDS WL STILL BE RATHER 
BREEZY.       /MJF

IN THE EXTENDED THURSDAY NIGHT THROUGH MONDAY...WE ARE STILL LOOKING 
AT A LARGE UPPER TROF CARVING OUT IN THE WRN CONUS AS TIME 
PROGRESSES. NOW HOW IT GETS THERE IS QUITE VARIANT AMONGST THE 
VARIOUS MODELS. IN GENERAL...THE LARGE UPPER LOW WE DEAL WITH IN THE 
MIDDLE OF THE WEEK SLOWLY EXITS TO THE EAST...WITH ANOTHER UPPER LOW 
MOVING INTO THE PAC NW ON FRIDAY AND FRIDAY NIGHT. THE GFS CONTS TO 
BE ON THE FAST SIDE OF MODEL SOLUTIONS IN PROGRESSING THE UPPER 
TROFFING EWD. THE 00Z ECMWF STILL LOOKED UNREASONABLE BUT THE 12Z 
ECMWF FINALLY CAME AROUND TO THE WRN CONUS DEEP UPPER TROF SOLUTION. 
OVERALL...THE CANADIAN GLOBAL STILL LOOKS THE MOST REASONABLE WITH 
THIS SOLUTION IN DRAINING DOWN LOW LEVEL ARCTIC AIR BY SUNDAY AND 
MONDAY...AND CARVING OUT A DEEP UPPER TROF IN THE WRN CONUS. 
ALTHOUGH I CANNOT RULE OUT SPRITS OF -SN HERE AND THERE SUN THRU MON 
WITH DEVELOPING OVERRUNNING/FRONTAL BANDING...THE MAIN CRUX OF THE 
PCPN LOOKS TO DEVELOP JUST BEYOND THE EXTENDED MON NIGHT AND TUE. 
MORE CERTAIN...IT DOES LOOK PRETTY DARN CHILLY SUN AND MON WITH THE 
ARCTIC AIR DRAINING DOWN FM WRN CANADA. THEREFORE WENT MUCH CLOSER 
TO THE CHILLY MEX TEMPERATURES ON SUN AND MON AS OPPOSED TO THE 
WARMER HPC READINGS. JUST DOES NOT LOOK VERY PLEASANT SUN AND MON.
/MJF 

&&

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

$$