FXUS63 KFSD 290930
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
330 AM CST SUN NOV 29 2009

.DISCUSSION...
TEMPERATURES REMAIN THE PRIMARY FOCUS OF THE FORECAST THROUGH THE 
NEXT FEW DAYS...WITH THE STREAK OF ABOVE NORMAL READINGS CONTINUING 
INTO TUESDAY BEFORE STRONG COLD FRONT PLUNGES SOUTHWARD TUESDAY AND 
TUESDAY NIGHT.

FOR TODAY...FAIRLY WIDESPREAD AREA OF STRATUS TO OUR NORTH POISED TO 
SLIDE INTO CENTRAL/EASTERN PORTIONS OF THE CWA THIS MORNING. STRATUS 
WILL LINGER LONGEST INTO THE EARLY-MID AFTERNOON ACROSS PORTIONS OF 
SOUTHWEST MINNESOTA/NORTHWEST IOWA...AND WILL KEEP HIGH TEMPERATURES 
THERE CLOSER TO COOLEST GUIDANCE IN THE MID TO UPPER 30S. MORE SUN 
AND MODEST MIXING WITH WEST-NORTHWEST FLOW SHOULD YIELD MID 40S FOR 
AREAS WEST OF THE JAMES RIVER.

VERY MILD AIR AGAIN TAKING OVER FOR MONDAY WITH 925MB TEMPS OF +5C 
IN THE NORTHEAST CWA TO +10C IN THE SOUTHWEST. COULD HAVE SOME MID 
LEVEL WARM ADVECTION CLOUDS DEVELOP OVER THE CWA TONIGHT AND LINGER 
OVER THE NORTHEAST CWA EARLY IN THE DAY...BUT SHOULD MOVE OUT OF THE 
AREA BY EARLY AFTERNOON AND WOULD NOT EXPECT THEM TO HAMPER WARMING 
TOO MUCH AS STRONGER WESTERLY FLOW SHOULD ALLOW FOR STRONG MIXING. 
MOST AREAS SHOULD SEE HIGHS ABOUT 10 DEGREES WARMER ON MONDAY THAN 
TODAY.

NEXT COUPLE OF NIGHTS WOULD EXPECT TO SEE SOME ELEVATION DEPENDENT 
TEMPS ACROSS THE AREA WITH RELATIVELY LIGHT THOUGH NOT COMPLETELY 
CALM WINDS. WARMEST READINGS WILL LIKELY BE ACROSS GREGORY COUNTY 
AND ALSO EAST OF THE BUFFALO RIDGE IN SOUTHWEST MINNESOTA...WHERE 
LOW LEVEL FLOW FROM THE SOUTHWEST FAVORS GOOD DOWNSLOPE. THIS COULD 
BE MORE DRAMATIC MONDAY NIGHT THAN CURRENTLY FORECAST...AND LATER 
SHIFTS MAY HAVE TO WARM THE FAR NORTHEAST FURTHER AS 925MB TEMPS 
CLIMB TO +6C BY 12Z TUESDAY.

COLD FRONT PUSHES THROUGH THE CWA TUESDAY...AND ASIDE FROM THE 
OPERATIONAL GFS STILL BEING ON THE FAST SIDE WITH THE SURFACE 
BOUNDARY...MODELS SEEM TO BE SETTLING ON TIMING SIMILAR TO PREVIOUS 
FORECAST...PUTTING THE FRONT IN THE SOUTHEAST CORNER OF OUR CWA BY 
00Z WEDNESDAY. TIMING OF LOW LEVEL COOLING BEHIND THE FRONT SEEMS TO 
BE MORE IN QUESTION...WITH NAM SHOWING MUCH MORE AGRESSIVE 850MB 
COLD PUSH THAN EITHER ECMWF OR GEM. NAM ACTUALLY AMONG THE WARMEST 
MODELS AT 18Z AHEAD OF THE BOUNDARY...BECOMING ONE OF THE  COLDEST 
BY 00Z BEHIND THE FRONT. IF NAM TAKEN AT FACE VALUE...COULD SEE 
STRONGER NON-DIURNAL TREND TO TEMPS WITH READINGS WARMING QUICKLY BY 
MIDDAY...THEN FALLING OFF IN THE NORTHWEST THROUGH THE AFTERNOON... 
THOUGH INITIAL COOLING ALOFT MAY LEAD TO WARMER TEMPS BRIEFLY AS 
DEEPER MIXING RESULTS. HAVE NOT GOTTEN TOO AGRESSIVE WITH AFTERNOON 
COOLING DUE TO THIS...BUT DO HAVE TEMPS IN OUR NORTHWEST BECOMING 
FAIRLY STEADY AFTER 18Z AND TAILING OFF AFTER 21Z.

THIS COLD FRONT WILL SIGNAL TRANSITION BACK TO MUCH MORE SEASONAL 
AIR ACROSS THE REGION...WITH SUBZERO 850MB TEMPS BECOMING ENTRENCHED 
OVER THE AREA THROUGH THE END OF THE WEEK. WHILE THE MID-LATTER PART 
OF THE WEEK WILL FEEL MUCH COOLER...READINGS WILL GENERALLY BE CLOSE 
TO OR JUST A FEW DEGREES BELOW EARLY DECEMBER NORMALS.  /JH

&&

.AVIATION...
A NARROW BAND OF CIGS BETWEEN 1000 AND 2000 FT WILL MOVE SOUTHEAST 
ACROSS PORTIONS OF SW MN AND NW IA...EXITING THE AREA BY 12Z. 
ANOTHER AREA OF STRATUS...GENERALLY FROM 2000 TO 3000 FT WILL MOVE 
SOUTH FROM ND INTO ERN SD AND SW MN. THESE CLOUDS WILL REACH KHON... 
KBKX AND KMML BY 12Z AND SHOULD BE SOUTH OF I90 BY 15Z AND THROUGH 
KSUX AND KSLB BY 17Z. AS THE MORNING PROGRESSES...THE STEERING WINDS 
AT 925 MB WILL SHIFT TO NW RESULTING IN ADVECTION OF THE CLOUDS MORE 
TO THE EAST SUCH THAT KHON AND KMHE SHOULD BE VFR BY 15Z OR 16Z. 
EXPECT THAT THE OVC SKIES WILL MOVE EAST OF KFSD AND KSUX BY 19Z. 
HOWEVER...WITH COLD TEMPS ALOFT AND HEATING...SHOULD SEE STRATOCU 
REFORM WITHIN A COUPLE OF HOURS ON THE STRATUS. THIS WILL LIKELY 
AFFECT KFSD AND KBKX INTO THE AFTERNOON. ONCE THE SUNSETS BY 22Z 
EXPECT MAIN STRATUS TO BE EAST OF THE AREA WITH STRATOCU RAPIDLY 
DISSIPATING LEAVING VFR CONDITIONS. THEN EXPECT W TO NW FLOW TO 
CONTINUE THROUGH THE NIGHT. /SCHUMACHER

&&

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

$$
 JH/SCHUMACHER