FXUS63 KFSD 151548
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
947 AM CST TUE DEC 15 2009

.DISCUSSION...
COLD DAY WITH A RELATIVELY STRONG INVERSION TO WORK THROUGH. 
THUS...HAVE SLOWED DOWN WARMING A LITTLE AND DECREASED HIGHS JUST A 
TOUCH. BAND OF MID CLOUDS OVER SOUTHWEST CWA LOOKS LIKE IT WILL 
LIKELY STICK TOGETHER THROUGH THE DAY...SO INCREASED CLOUD COVER A 
LITTLE OVER THE SOUTH INTO THE AFTERNOON. THE WIND CHILL ADVISORY 
WAS ALLOWED TO EXPIRE AND FOR THE MOST PART WIND CHILL VALUES WILL 
IMPROVE THROUGH THE DAY. THE NORTHERN TIER OF COUNTIES COULD STAY 
AROUND 25 BELOW FOR A COUPLE MORE HOURS...BUT WITH WIND SPEEDS OF 
ABOUT 5 TO 10 MPH...SO NOT A MAJOR THREAT. /08

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL THRU 12Z WED. WEAK MID-UPPER LEVEL WAVE 
MAY PRODUCE CIGS AOA 10KFT AFTER 15/21Z...MAINLY ALONG AND NORTH OF 
INTERSTATE 90. JH

&&

.PREV DISCUSSION...
ANOTHER COLD DAY IN STORE AS 1040 MB HIGH SHIFTS ACROSS THE AREA. 
WIND CHILL ADVISORY REMAINS IN EFFECT FOR THE NRN AND ERN CWA 
THROUGH MID MORNING WITH WIND CHILLS 20 TO 30 BELOW ZERO. 
TEMPERATURES WILL SLOWLY MODERATE TODAY...BUT WITH RELATIVELY LIGHT 
WINDS...WIND CHILLS WILL BE MUCH IMPROVED BY THIS AFTERNOON. WILL 
SEE SOME THIN CIRRUS MOVE ACROSS THE AREA LATER TODAY BUT SHOULD 
HAVE LITTLE AFFECT ON HIGH TEMPERATURES. 

LOW TEMPERATURE FORECAST IS A BIT TRICKY TONIGHT...AS GRADIENT WIND 
WILL KEEP TEMPERATURES FROM FALLING MUCH AT ALL...ESPECIALLY IN 
THE WEST. EXPECTING A 5 TO 10 DEGREE DROP IN THE EAST LATE 
AFTERNOON/EARLY EVENING WHERE THE SFC GRADIENT WILL BE WEAKER NEAR 
THE SFC HIGH CENTER. GRADIENT WILL INCREASE QUITE A BIT THROUGH THE 
EVENING...AND AS WINDS INCREASE...TEMPERATURES WILL LEVEL OFF AND  
BEGIN TO RISE. ACTUALLY...THEN LOW LEVEL JET GETS CRANKING OVER THE 
ERN CWA BY LATE THIS EVENING...WHICH COULD WARM TEMPERATURES BEYOND 
THE CURRENT FORECAST...ESPECIALLY IF SOME 20 KT PLUS MIX TO THE SFC. 
INCREASED WIND SPEED ABOVE GUIDANCE IN THESE AREAS FOR LATE 
TONIGHT...BUT MAY NOT BE ENOUGH.  

FOR WEDNESDAY...HIGH TEMPERATURES REALLY DEPEND ON HOW MUCH ARCTIC 
AIR GETS SCOURED OUT BY SW WINDS AND HOW DEEP THE ATMOSPHERE MIXES. 
GUIDANCE SEEMED TO COLD...ESPECIALLY THE NAM...WHICH SHOULD IT 
VERIFY WOULD MEAN NO MIXING. THINKING MIXING CLOSE TO 925 MB IS 
MORE REALISTIC...WHICH WOULD PUSH HIGHS INTO THE 20S AND EVEN SOME 
30S INTO THE SW. 

MODELS CHANGED QUITE A BIT FROM LAST NIGHTS RUNS FOR LATER PORTIONS 
OF THIS WEEK. CANADIAN...GFS...AND NAM ALL KEEPING CLIPPER LIKE 
WAVES WELL NORTH OF THE CWA...SO BASICALLY NO CHANCE FOR 
PRECIPITATION UNTIL THU NIGHT. ALSO...THIS MEANS WARMER TEMPERATURES 
INTO THE LATE HALF OF THE WEEK. THURSDAY COLD BE A RATHER WARM 
DAY...ESPECIALLY IN COMPARISON TO THE LAST FEW WEEKS. KEPT FORECAST 
HIGHS ABOVE GUIDANCE...AS THU LOOKS FAVORABLE FOR MIXING UNDER LIGHT 
WRLY FLOW. BEST CHANCE FOR PRECIPITATION WILL BE INTO S CNTRL SD 
WITH A WAVE WHICH SLIDES ACROSS WRN SD...INTO CNTRL NE THU NIGHT. 
MOST OF THE ENERGY SHOULD STAY W AND S OF THE CWA. INVERTED THROUGH 
HANGS OVER THE AREA FRI AND FRI NIGHT...SO KEPT SOME SMALL CHANCE 
FOR MEASURABLE SNOW GOING ACROSS THE CWA. 97

&&

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

&&

$$