FXUS63 KFSD 011617
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1015 AM CST TUE DEC 1 2009

.DISCUSSION...
FRONT ON TRACK SO FAR THIS MORNING...WITH INITIAL WIND SHIFT TO 
NORTHWEST JUST EAST OF KBKX-KYKN LINE AS OF 1535Z SURFACE OBS. 
STRONGER WINDS WILL AWAIT SHOT OF COLD ADVECTION ALOFT WHICH WILL 
ALLOW FOR BETTER MIXING...AND CURRENT TIMING OF WIND ADVISORY IN OUR 
WEST LOOKS GOOD. A LITTLE QUESTIONABLE THAT AREAS SOUTH OF I-90 WILL 
REACH ADVISORY CRITERIA WITH STRONGEST COLD ADVECTION AND BETTER 
PRESSURE RISES AIDING THE STRONGER WINDS IN MIXING DOWN ACROSS THE 
NORTH...BUT DO HAVE SOME ELEVATION ASSISTANCE IN GREGORY COUNTY AREA 
SO WILL LEAVE IT AS IS FOR NOW.

TEMPERATURES MORE TRICKY...AS EXPECT TO SEE QUICK WARMING WITH 
INITIAL MIXING...FOLLOWED BY STEADY TO FALLING TEMPS AS COLDER AIR 
WORKS IN ALOFT. OVERALL...FORECAST HIGHS LOOK PRETTY REASONABLE BUT 
WILL HAVE TO PLAY WITH HOURLY TRENDS A BIT. NO UPDATE TO ZFP PLANNED 
AT THIS TIME. WILL HAVE NEW GRIDS PFM OUT SHORTLY.   /JH

&&

.AVIATION...
PRIMARILY VFR EXPCD THRU 09Z TNGT...THOUGH PATCHY BKN MVFR CIGS 
POSSIBLE THIS AFTERNOON ALONG/WEST OF THE JAMES RIVER. BETTER CHANCE 
OF MVFR CIGS WORKING SOUTHWARD INTO HIGHWAY 14 CORRIDOR AFTER 09Z 
AND PUSHING INTO I-90 CORRIDOR AFTER 14Z WEDENSDAY. 

STG NWLY WINDS...SUSTAINED AT 25-30KTS WITH BRIEF GUSTS TO 40 KTS 
WILL BE FOUND BEHIND A CDFNT TODAY...REACHING THE JAMES VALLEY BY 
18Z. STG WINDS WILL CONTINUE TO EXPAND EAST THROUGH THE AFTERNOON... 
REACHING I-90 BY 21Z. WINDS SHOULD DECOUPLE AFTER 23Z AS SUN SETS... 
THOUGH GUSTS AOA 25KTS WILL PERSIST THROUGH THE EVENING...ESPECIALLY 
EAST OF THE JAMES VALLEY.   /JH

&&

.PREV DISCUSSION...
MAIN CHALLENGES FOR TODAY WILL BE TEMPERATURES AND WINDS WITH THE 
PASSAGE OF A STRONG COLD FRONT THROUGH THE AREA. EARLY THIS 
MORNING...THE COLD FRONT IS STILL BARELY NUDGING INTO EXTREME 
NORTHWESTERN SOUTH DAKOTA...THOUGH EXPECTING IT TO BE APPROACHING 
OUR FAR WESTERN CWA BY 12Z. MODELS IN PRETTY GOOD AGREEMENT ON 
TIMING OF THE FRONT...WHICH WOULD GET IT INTO OUR FAR SOUTHEAST 
AROUND 21Z. STRONG COLD AIR ADVECTION WILL ENSUE BEHIND THE 
FRONT...AND WITH STEEP LOW LEVEL LAPSE RATES AND 2 TO 4 MB PRESSURE 
RISES WITH THE PASSAGE OF THE BOUNDARY...ELECTED TO ISSUE A WIND 
ADVISORY FOR PARTS OF THE JAMES RIVER VALLEY FOR THIS AFTERNOON 
WHERE 925/850 MB WINDS ARE PROGGED TO BE AROUND 30/45KT 
RESPECTIVELY. DAY SHIFT WILL HAVE TO WATCH TO SEE IF AN ADVISORY IS 
NEEDED FARTHER TO THE EAST LATER IN THE DAY. TEMPERATURES ARE ALSO 
TRICKY...DEPENDENT ON SPEED OF THE SYSTEM AND ANY CLOUD COVER WITH 
THE FRONT. AT THIS POINT...PREFRONTAL MIXING/WARMING SHOULD ALLOW 
OUR SOUTHEASTERN AREAS TO GET INTO THE LOWER TO MID 50S BEFORE THE 
FRONTAL PASSAGE. MODELS PROGGING A BAND OF MID CLOUDS WITH THE 
FRONT...SO COULD SEE TEMPERATURES FALL TEMPORARILY WITH THE PASSAGE 
OF THE FRONT...THEN COULD SEE A SLIGHT REBOUND...MAINLY IN OUR 
WEST...WITH BETTER MIXING AND BREAKS IN THE CLOUDS. IN ANY 
EVENT...LOOKS LIKE A GENERAL NONDIURNAL TREND WITH RESPECT TO 
TEMPERATURES.

WINDS WILL STAY UP TONIGHT...PREVENTING TEMPERATURES FROM COMPLETELY 
BOTTOMING OUT...THIS ALONG WITH BROKEN CLOUDS...WILL KEEP LOWS IN THE 
20S ACROSS THE AREA.

ON WEDNESDAY...THE UPPER LEVEL TROUGH REALLY BEGINS TO SETTLE INTO 
THE NORTHERN PLAINS...WITH LOWER CLOUDS INCREASING FROM THE NORTH 
THROUGH THE DAY. WHILE HIGHS ARE EXPECTED TO BE IN THE LOWER TO MID 
30S...WITH STOUT NORTHWESTERLY WINDS CONTINUING OVER THE 
REGION...WIND CHILLS WILL BE IN THE TEENS TO LOWER 20S. WITH A 
LITTLE DEEPER MOISTURE/CONTINUING CAA/AND WEAK LIFT OVER THE 
AREA...STILL THINKING WE COULD SEE SOME FLURRY ACTIVITY ON WEDNESDAY 
NIGHT INTO THURSDAY AS THE TROUGH CONTINUES TO DEEPEN OVER THE 
CENTRAL PART OF THE NATION. THE BRUNT OF THE COLD AIR WILL BE FELT 
ON THURSDAY AND THURSDAY NIGHT...WHEN 925 MB TEMPS WILL BE IN THE 
RANGE OF -8 TO -11 C ACROSS OUR CWA...SO LOOKING FOR HIGHS IN THE 
LOWER TO MID 20S WITH LOWS EITHER SIDE OF 10 DEGREES.

AIRMASS BEGINS TO MODERATE SLIGHTLY BY FRIDAY AS THE TROUGH AXIS 
MOVES TO THE EAST...WITH HIGHS A COUPLE OF DEGREES WARMER THAN 
THURSDAY...ESPECIALLY IN OUR WEST. LOOKS LIKE WE WILL HAVE A HARD 
TIME GETTING RID OF THE STRATOCU ON FRIDAY...THOUGH MAY SEE A 
DECREASE IN CLOUDS IN OUR WEST BY LATER IN THE AFTERNOON.  /JM

&& 

.FSD WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
MN...NONE.
NE...NONE.
SD...WIND ADVISORY FROM NOON TODAY TO 6 PM CST THIS EVENING FOR 
     SDZ038-039-050-052>054-057>060-063-064.

&&

$$
 JH