FXUS63 KFSD 041034
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
435 AM CST FRI DEC 4 2009

.DISCUSSION...
WNWLY FLOW OF COLD AND FAIRLY MOIST LOW LVL AIR OVER CWA WITH 
PATCHWORK OF SC CLOUDS AND SCT FLUR THIS MRNG. THIS SHOULD GET 
SCOURED OUT FM W TO E OVER THE CWA THIS AFTN WITH DRYING AND
WARMING FM ALOFT. HOWEVER...NOT CONDUCIVE TO MUCH MIXING AND
WITH LIGHT SNOW COVER...CUT BACK HIGHS A LIT FOR TDA. TEMPS SHOULD 
DROP PRETTY FAST THIS EVE WITH CLRG AND BEFORE SSWLY FLOW KICKS IN. 
SATURDAY BEST DAY OF FCST WITH SOME MIXING DOWN OF WARMER AIR FROM 
ALOFT...MAINLY IN SRN CWA...WITH SNOW COVER RESTRICING WARMING UP 
NORTH ESP FM BKX TO SWRN MN. THEN THE USUAL ADVENTURE WITH FLIP/ 
FLOPPING MODELS. GFS DID A SWAP WITH THE NAM FM YESTERDAY FOR THE 
LATE SUN SYSTEM...WITH NOW THE GFS MUCH WEAKER AND FURTHER SOUTH. 
HOWEVER...CANADIAN AND ECMWF STILL SUPPORT CHCS -SN DVLPG NEWD INTO 
THE CWA MAINLY SOUTH OF I90 BY SUN NGT WITH SHORT WAVE AND LOBE OF 
ISENTROPIC LIFT...WITH STILL AN INCH OR TWO PSBL MAINLY NWRN IA...
SO WILL NOT DROP THE BALL BASED ON THE GFS. THIS MODEL ALSO ALL OVER 
THE PLACE WITH PSBLY MAJOR WAVE CRASHING NEWD INTO THE CNTRL PLAINS 
TUES...AND THE NOTORIOUS 06Z GFS RUN HAS REALLY BACKED OFF. BUT A 
COMPOSITE OF THE ECMWF...CANADIAN...AND GFS WOULD STILL IMPLY A 
PRETTY GOOD CHC OF AT LEAST LIGHT SNOW MOVING NEWD OVER THE SERN HLF
OF THE CWA LATER MON NGT INTO TUES NGT...SO UPPD THE POPS SOME FM 
PREV FCST. OTRW CUT BACK THE TEMPS SOME ACROSS THE BOARD FM SUN THRU 
TUES WITH NRN STREAM DOMINATION OF CANADIAN AIR AND POTENTIALLY NEW 
SNOW. HOPEFULLY LATER RUNS OF THE GFS WILL SETTLE DOWN TO SOME KIND 
OF SOLUTION FOR LATER FCSTS./ RYRHOLM

&&

.AVIATION...
THERMAL PROFILES MAKING IT FAIRLY DIFFICULT TO GET A FULL PICTURE OF 
WHAT THE LOWER VFR/UPPER MVFR CLOUD COVER REALLY IS THIS MORNING...
AND VISFOG SATELLITE IMAGERY AT TIMES NOT MATCHING UP TOO WELL TO 
OBSERVATIONS TO THE NORTHWEST OF THE AREA. EVEN WITH SOME CLEARING 
PATCHES...WL LKLY FIND SELF DESTRUCTIVE TENDENCY TDA BEFORE LARGER 
SCALE RIDGING AIDS CLEARING FROM W TO E THRU THE AFTN. THREAT FOR 
MVFR VSBYS WITH FLURRIES AND LIGHT SNOW APPEARS TO BE OVER...AT 
LEAST TO A DEGREE THAT WARRANTS MENTION IN THE TAFS...BUT THROUGH AT 
LEAST 11-13Z WL FIND FLURRIES WITH CLOUD TMPS ANCHORED WELL WITHIN 
THE DENDRITIC...AND WL LKLY CONTINUE WELL INTO THE DAY ONCE CLOUDS
REDEVELOP WITH HEATING AND/OR WRAP SEWRD THRU FAR ERN SD/SW MN. 
/CHAPMAN

&&

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

$$