000 
FXUS63 KFSD 231041
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
400 AM CST WED NOV 23 2005

.DISCUSSION...
AS HAS BEEN ADVERTISED...SOME BIG CHANGES ARE ON THE WAY.  
TEMPERATURES HAVE BEEN RISING OVER MOST OF THE CWA DURING THE 
OVERNIGHT HOURS...AND PLACES IN THE CENTRAL AND EASTERN PORTIONS OF 
THE AREA WILL MOST LIKELY SEE HIGHS REACHED DURING THE EARLY 
AFTERNOON AS STRONG CAA BEGINS TO TAKE PLACE.  850 MB TEMPS BEGIN TO 
DROP OFF DRASTICALLY AFTER 18Z...BEING IN THE RANGE OF 0 TO -12 FROM 
SOUTHWEST TO NORTHEAST RESPECTIVELY BY THIS EVENING.  IT DOES LOOK 
TO BE WINDY THIS AFTERNOON...BUT BELIEVE IT WILL REMAIN BELOW 
ADVISORY CRITERIA WITH 850 WINDS REMAINING AROUND 40 KTS AND 925 
WINDS AROUND 35 KTS AT THEIR HIGHEST.  WHILE 950 TO 925 MB LAPSE 
RATES BY LATER THIS AFTERNOON WILL SUPPORT GOOD MIXING...THE MSLP 
GRADIENT MAGNITUDE IS NOT ESPECIALLY THAT IMPRESSIVE AND 300 AND 850 
MB Q VECTORS WILL BE WORKING AGAINST LOWER LEVEL WINDS...SO JUST 
DONT FEEL IT WILL BE A BIG WIND EVENT.  WITH THE STRONG CAA AND 
LOWER LEVEL MOISTURE AND LOW LEVEL FRONTOGENESIS...KEPT SCATTERED 
FLURRIES IN THE FORECAST FOR TONIGHT OVER THE CWA...BUT MUCH DRIER 
AIR FILTERING INTO THE REGION WILL SHUT THIS DOWN FROM NORTHEAST TO 
SOUTHWEST BY 12Z ON THURSDAY.  STILL LOOKS TO BE A MUCH COLDER DAY 
ON THANKSGIVING...WITH MODELS IN GOOD AGREEMENT ON 850 TEMPS IN THE 
-4 TO -13 RANGE OVER THE FA.  WITH THE BAROCLINIC BAND SETTING UP 
JUST TO THE WEST OF OUR CWA ON THURSDAY...COULD STILL SEE A FEW 
FLURRIES THROUGH THE DAY IN THE FARTHEST SOUTHWESTERN COUNTIES OF 
OUR CWA.  BAROCLINIC BAND ALONG WITH WAA WILL BEGIN TO PROGRESS BACK 
TO THE EAST ON THURSDAY NIGHT...PRODUCING SCATTERED SNOW 
SHOWERS...MOVING FROM WEST TO EAST ACROSS THE CWA THROUGH EARLY 
FRIDAY AFTERNOON.  BEST CHANCE OF POPS WILL BE IN THE NORTH WHERE 
THE UPPER LEVEL FORCING IS HIGHEST.  I TOOK OUT THE CHANCE OF 
FREEZING RAIN ON THE BACKSIDE OF THE PRECIPITATION SHIELD ON 
FRIDAY...AS IT APPEARS THAT THE PRECIPITATION WILL BE OVER BY THE 
TIME TEMPERATURES ALOFT RISE ABOVE FREEZING.  PRETTY SIGNIFICANT 
WARMING FOR FRIDAY AND SATURDAY...BEFORE ANOTHER SHOT OF REINFORCING 
COLD AIR COMES IN ON SATURDAY NIGHT.

MAIN CHALLENGE IN THE EXTENDED SUN THRU WED IS THE POTENTIAL FOR A 
WINTER STORM...AT LEAST OVR THE ERN HALF OF THE FA...IN THE SUN 
NIGHT THRU MON NIGHT TIMEFRAME. LATEST 00Z GFS HAS BEGUN TO LIFT THE 
LARGE UPPER/SFC LOW FURTHER TO THE N WHEN COMPARED TO YESTERDAYS 
00Z RUN...WHEN THE NRN STREAM WAS FIRMLY ENTRENCHED ACROSS THE NRN 
HALF OF THE U.S. NOW THE 00Z GFS HAS RETREATED THE NRN STREAM BRANCH 
UP TO THE NRN TIER OF THE U.S...ALLOWING FOR A PROGRESSION OF THE 
SFC LOW INTO THE LOWER MO RIVER VALLEY ON MONDAY. BELIEVE THAT EVEN 
THIS IS TOO FAR SOUTH...AS USUALLY THE RIDGING AHEAD OF THESE 
DEEPENING UPPER LOWS MOVG OUT OF THE SRN RCKYS IS MODELED TOO WEAK. 
THUS...SRN STREAM SYSTEMS HAVE A TENDENCY TO LIFT FURTHER NWD THAN 
ORIGINALLY FCST. THIS IS BACKED UP BY THE 00Z CANADIAN AND 00Z ECMWF 
IN A MAJOR WAY...IN THAT THESE TWO MODELS LIFT THE SFC LOW FROM THE 
SRN PLAINS TO THE NRN MS VALLEY FM SUN NIGHT THRU MON NIGHT. THAT 
TRACK WOULD DEFINITELY BE FAVORABLE FOR A MAJOR EVENT IN OUR 
FA...BUT IT IS A LONG WAY OUT. DAYSHIFT WL HAVE TO REALLY PERUSE OVR 
THIS FOR THE DETAILS...BUT I BEGAN A TREND OF COOLING THINGS OFF 
SUNDAY THRU TUESDAY AND EVEN INTRODUCED A CHC OF RA/SN OR SN SUN AND 
SUN NIGHT JUST BEHIND THE INVERTED TROF. H85 TEMPS ARE STILL A BIT 
WARM IN OUR E ON SUNDAY WITH A TIGHT BAROCLINIC ZONE OVR THE CWFA 
BUT CLOUD COVER...AND CYCLOGENESIS TO OUR S MAY WRAP SOME COOL AIR 
INTO THE SYSTEM FM THE E. ATTM...STILL HAVE SOME RA/SN CHCS IN ON 
MONDAY MINUS SW MN WHERE PURE SN SHOULD FALL...BUT DAYSHIFT WL HAVE 
TO REEVALUATE THE COLD AIR DRAINAGE INTO OUR CWFA FM THE E AND NE AS 
IT COULD BE PURE SNOW IF THE CYCLOGENESIS IS STRONG ENUF.  


&&

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

&&

$$

JM/MF