FXUS63 KFSD 150330
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
930 PM CST MON DEC 14 2009

.DISCUSSION...
VIRTUALLY CLR SKIES IN MOST THE CWA ATTM AND EARLIER CUT BACK SKY 
COVER QUITE A BIT FM PREV GRIDS. WNWLY FLOW OF VERY COLD DRY AIR...
BUT LOOKS LIKE ANOTHER SURGE OF COLD ADVECTION PRECDD BY MID CLDS 
MOVG THRU CNTRL SD TOWARDS CWA...SO WILL BRING THIS ACROSS DURG THE 
NGT...FLWD BY SOME MORE CLRG...A MUCH BIGGER TEMP DROP...AND ENUF
OF A NW BREEZE TO KEEP THE WIND CHILL ADVY NRN TO ERN CWA. MIGHT 
EVEN GET 10 MPH PLUS WINDS TO REALLY GET THE WIND CHILLS WELL INTO 
THE CRITERIA...BUT PROBABLY A LIT LATER THAN THE PREV FCST OVERALL.
RYRHOLM

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL THRU 00Z WED. AREA OF MID LVL CLOUDS
WITH WK SECONDARY WAVE SLIDING THRU SHUD LARGELY BE ON THE DECREASE
AS THE MASS SHIFTS TO THE SE THRU THE LTR EVNG AND OVERNIGHT...
BUT SHUD BE DECREASING IN COVERAGE AS FRONTOGENETIC FORCING WKNS.
BEST THREAT FOR A BRIEF PERIOD OF VFR CIG WOULD OCCUR ARND KHON AND 
KSUX. /CHAPMAN

&&

.PREV DISCUSSION...
MAIN CHALLENGE TONIGHT WILL BE THE AMOUNT OF CLOUD COVER AND HOW 
COLD TEMPERATURES WILL GET WITH AS BITTERLY COLD AIR CONTINUES TO 
FILTER IN BEHIND EXITING SYSTEM. PRESENT SATELLITE/OBS SHOWING 
CLOUDS BREAKING UP ACROSS THE AREA...WITH A FEW ISOLATED FLURRIES AS 
WEAK WAVE CROSSES THE CWA. ANTICIPATE THIS FLURRY ACTIVITY TO 
DIMINISH THROUGH THE LATE AFTERNOON AS THE WAVE PUSHES EAST...WITH 
CLOUDS CONTINUING TO BREAK UP UNDER A DRY NORTHWESTERLY FLOW. MAY 
SEE A FEW MORE MID CLOUDS LATE TONIGHT AS ANOTHER WEAK WAVE SWINGS 
OUT OF THE NORTHERN ROCKIES. ALSO EXPECTING WINDS TO DIMINISH 
OVERNIGHT AS SURFACE RIDGING BUILDS INTO THE AREA...HOWEVER WITH 
RAPIDLY FALLING TEMPERATURES DURING THE EVENING...WILL BEGIN TO 
FLIRT WITH WIND CHILL ADVISORY CRITERIA. WL GO WITH WIND CHILL ADVY 
ACRS NRN AND ERN CWA WHERE WINDS AND AIR TEMPS WL PUSH WIND CHILLS 
TO CRITERIA LEVELS. DOES APPEAR THAT THE HIGHER ELEVATIONS OF OUR 
NORTHEAST WOULD STAND THE BEST CHANCE OF HOLDING ON TO THE HIGHER 
WINDS. WENT ON THE LOW SIDE OF GUIDANCE WITH RESPECT TO 
LOWS...RANGING FROM NEAR -20 IN OUR NORTHWEST TO AROUND -10 IN OUR 
SOUTH.  /JM

WITH A COLD START TO TUES MORN AND SFC RIDGE AXIS ACRS WRN CWA...WL 
BE HARD TO WARM UP ACRS ERN CWA ON TUES AND WL STRUGGLE TO GET MUCH 
ABOVE 5 ABOVE. WEAK WAA ACRS WRN CWA IN AFTN WL ALLOW TEMPS TO RISE 
TO 10 TO 15 ABOVE ACRS THE SW. STRONGER WAA ALOFT WL SPREAD ACRS CWA 
TUES NIGHT ALONG WITH SOME INCREASING CLOUDS. SO EXPECT LOWS TO 
OCCUR IN THE EVE FOLLOWED BY SLOWLY RISING TEMPS. AM EXPECTING A 
QUICK DROP OFF IN TEMPS TO 5 TO 10 BELOW ACRS THE E IN THE EARLY EVE 
AND THEN RISE TO ABOVE ZERO LATER IN THE NIGHT AS LOW LEVEL SLY FLOW 
INCREASES. ACRS THE WEST...AM ALSO EXPECTING LOWS IN THE EVE...JUST 
NOT SUB ZERO. 

WL BE WARMER ACRS CWA ON WED...BUT LOW LEVEL SELY FLOW AHEAD OF 
QUASI WARM FNT ACRS FAR SWRN CWA WL KEEP MOST OF CWA BLO NORM...BUT 
AT LEAST IN THE UPPER TEENS TO LOWER 20S FOR HIGHS. PBLY WL WARM 
INTO LOWER 30S ACRS SWRN CWA WHERE SFC FLOW WL BECOME A LTL MORE 
SWLY. 

ANOTHER WEAK S/W AND ASSOCD WAA WL MOVE ESEWD ACRS CWA WED NITE AND 
THIS WILL HELP HOLD TEMPS UP ABOVE ZERO. CUD SEE A FEW FLURRIES WITH 
THIS S/W BUT FOR NOW WL LEAVE DRY. 

LOOKS LIKE THU WL BE THE WARMEST DAY IN THE 7 DAY FCST. SHUD BE A 
FEW DEG ABOVE NORM AHEAD OF NEXT S/W WHICH WL MOVE SEWD ACRS CWA 
LATER THU NITE INTO FRI MORN. THIS S/W WL BRING ANOTHER SHOT OF 
COLDER AIR INTO CWA FOR FRI INTO SUN. THE COLDER AIR ASSOCD WITH 
THIS FEATURE NOT AS COLD AS CURRENTLY ACRS CWA...SO WL ONLY SEE 
HIGHS 5 TO 10 DEG BLO NORM FRI INTO SUN WITH LOWS IN THE SINGLE 
DIGITS. DID KEEP SMALL CHC OF LIGHT SNOW IN FCST FOR FRI AS WEAK SFC 
LOW DROPS SEWD ACRS MN ASSOCD WITH S/W. MAY NEED TO UP POPS ACRS SW 
MN AS WE GET CLOSER TO EVENT...DEPENDING ON EXACT TRACK OF SFC WAVE 
AND S/W. 

&&

.FSD WATCHES/WARNINGS/ADVISORIES...

IA...WIND CHILL ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST 
     TUESDAY FOR IAZ002-003-014-022.

MN...WIND CHILL ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST TUESDAY 
     FOR MNZ071-072-080-081-089-090-097.

NE...NONE.
SD...WIND CHILL ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST TUESDAY 
     FOR SDZ038>040-052>056.

&&

$$