FXUS63 KFSD 030223
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
825 PM CST WED DEC 2 2009

.DISCUSSION...
HAVE UPDATED THE FCST AND GRIDS FOR AN EXPECTED INCREASE IN SNOW 
SHOWERS AFTER 06Z N OF I90 AS UPPER LOW DROPS SEWD INTO SW MN BY 12Z 
THU. FAIRLY LARGE AREA OF SNOW SHOWERS ASSOCD WITH THIS FEATURE OVR 
NERN SD/SERN ND INTO WCNTRL MN ATTM AND THIS SHUD CONT TO SPREAD SWD 
WITH UPPER LOW. SO HAVE INCREASED POPS TO LIKELY N OF I90 AFTER 06Z 
AND WL KEEP CHC TO THE S. CUD SEE 1/2 TO 3/4 OF AN INCH SNOW AFTER 
06Z WITH THE UPPER LOW ESPEC ACRS CNTRL SD AND PSBLY INTO SW MN. 
PREVIOUS SNOW SHOWERS THAT MOVED ACRS CWA THIS EVE ARE DISSIPATING 
WITH LOSS OF DAYTIME HEATING...BUT AS STATED ABOVE...MORE SNOW 
EXPECTED AFTER 06Z. ALSO NW WINDS SHUD INCREASE ACRS NRN CWA LATER 
TONIGHT AS SFC BDNRY ASSOCD WITH UPPER LOW REACHES I90 BY MORNING.  

&&
.AVIATION...
SCATTERED SNOW SHOWERS CAN BE EXPECTED THROUGH 00Z THURSDAY. 
VISIBILITIES MAY BRIEFLY FALL TO AROUND 1 SM IN HEAVIER 
SHOWERS...HOWEVER...VISIBILITIES REDUCTION SHOULD BE SHORT LIVED. 
COULD PUT TEMPO GROUPS THROUGH NEARLY ENTIRE TAF 
PERIOD...HOWEVER...FOCUSED TEMPO GROUPS AROUND AREAS OF STRONGER 
LIFT MOVING THROUGH. AS UPPER LEVEL WAVE MOVES OUT OF NORTH DAKOTA 
THIS EVENING...EXPECT MVFR CEILINGS TO BECOME MORE WIDESPREAD.  
NORTHWEST WINDS WILL BECOME GUSTY WITH A LITTLE DAYTIME MIXING ON 
THURSDAY...MAINLY IN THE 15 TO 20 KNOT RANGE WITH SLIGHTLY HIGHER 
GUSTS. /BT

&&

.PREVIOUS DISCUSSION...
CONVECTIVE SNOW SHOWERS WHICH DEVELOPED THIS AFTERNOON ARE EXPECTED 
TO DIMINISH WITH LOSS OF HEATING TOWARD SUNSET. UPPER LEVEL WAVE AND 
ASSOCIATED BACKDOOR COLD FRONT WILL DROP SOUTH INTO OUR CWA TONIGHT 
AND PRODUCE ADDITIONAL ROUND OF SNOW SHOWERS. SHOULD BE FAIRLY QUICK 
MOVING SHOWERS AND DO NOT EXPECT MUCH ACCUMULATION...THOUGH A TENTH 
OR TWO NOT OUT OF THE QUESTION WITH FAVORABLE SNOW GROWTH TEMPS NEAR 
TOP OF STRATUS LAYER. GUIDANCE LOW TEMPS IN THE MID TEENS TO NEAR 20 
LOOK REASONABLE AND DID NOT STRAY MUCH FROM THAT.

WITH UPPER LOW OVER FCST AREA ERY THU MRNG...AND SECONDARY LOBE 
DROPPING SWD OVER AREA AS LOW BEGINS TO PULL OUT...SNOW SHWR 
POTENTIAL SHUD CONT THRU MOST OF THU OVER ALL OF FCST AREA. AGAIN 
LIMITED MOISTURE LVLS AND SPOTTY NATURE OF MEASRBL SNOW SHUD KEEP 
ANY ACCUMS TO THE DUSTING LEVEL WITH NOTABLE BUT VERY BRIEF VSBY 
DECREASES. SUPPORT DECREASES THU NGT AS LO LVL MOISTURE LINGERS...SO 
WILL GO WITH FLRYS. CLDS SHUD GRDLY DCRS FROM THE W/SW FRI AND FRI 
EVE. TEMPS WILL BE COLD...THAT IS NOT TOO MUCH BLO NORMAL...WITH 
GUIDNCE HAVING A REASONBL HANDLE ON TEMPS. CLDS WILL KEEP DIURNAL 
RANGE FAIRLY LIMITED. FOR A FAIRLY BENIGN SAT...THAT IS DRY AND 
PTCLDY...A LTL COLDER LOWS AND SLGTLY WARMER HIGHS CAN BE EXPECTED.

MODELS FAIRLY CONSISTENT ON SHOWING WAVE APPCHG FOR SUN AND SUN NGT 
WITH SOME LIMITED THERMAL CONTRAST AND MOISTURE AVBL FOR LGT SNOW 
DVLPMNT. CANADIAN AND ECMWF A LTL SLOWER BUT FAVOR FASTER GFS WHICH 
SEEM TO BE SUPPORTED BY THE LAST 2 NAM RUNS AT H84. WILL KEEP POPS 
LOW WITH SYS DUE TO BE DAMPENED SOME AS IT APPROACHES...AND ALSO 
TIMING QUESTIONS...BUT WILL MENTION THE LGT SNOW CHC FOR ALL OF FCST 
AREA FOR SUN AND SUN NGT. A BREAK MON...THEN WILL KEEP ANOTHER SLGT 
CHC FOR MON NGT AND TUES...WITH ANOTHER DRY DAY FOR THE LAST DAY OF 
THE FCST WHICH IS WED. MEANWHILE...TEMP VARIATIONS WILL NOT BE VERY 
STG WITH A LTL COOLING FOR SUN AND MON...AND SLGT WARMING AGAIN BY 
WED.

IN SHORT...NEXT SVRL DAYS CUS SEE SOME PDS OF LGT SNOW OR 
FLRYS...BUT NOT ENUF THERMAL CONTRAST MOISTURE OR ORGANIZATION OF 
PATTERN TO BRING MORE THAN PRETTY LIGHT ACCUMS...WHICH IS GOOD SINCE 
TIMING OF INDIVIDUAL WEAK WVS WILL BE TRICKY. TEMPS WILL SEE 
VARIATIONS ONLY TO THE EXTENT THAT HIGHS WILL STAY IN THE 20S OR 30S.
&& 

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

$$