000
FXUS63 KFSD 232118
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
320 PM CST MON NOV 23 2009

.DISCUSSION...
UPPER LEVEL WAVE PROGRESSING EAST ACROSS NEBRASKA SHOULD BEGIN TO 
INTERACT WITH THE INVERTED TROF/LOW TO MID LEVEL FRONT OVER THE NEXT 
SEVERAL HOURS. INITIAL SIGNS OF THIS ACTIVITY OCCURRING OVER 
NORTHWEST IOWA AT 2030Z...AND SHOULD SEE SOMETHING CLOSE TO THIS 
AREA EXPAND THROUGH THE EVENING. UPPER LEVEL PV ANOMALY SURGES INTO 
NW IA BETWEEN ABOUT 0Z TO 3Z AND SHOULD SET UP A NICE BAND OF RAIN. 
INSTABILITY NOT TOO BAD WITH THIS SYSTEM AND APPEARS THAT SOMETHING 
CLOSE TO THE 750MB FRONT SHOULD BE THE MOST ACTIVE. THIS WOULD PLACE 
THE BETTER CHANCE FOR RAIN FROM ABOUT VERMILLION TO WORTHINGTON 
EARLY THIS EVENING...THEN SHIFTING EAST OF THIS LINE BY LATE EVENING 
INTO THE OVERNIGHT HOURS. THE 650-700MB FRONT STILL LINGERING BACK 
FARTHER WEST...SO WILL KEEP LOWER POPS IN BY INTERSTATE 29 THROUGH 
12Z. OTHERWISE...TEMPERATURES WILL BE FAIRLY MILD BEHIND THE 
INCOMING WIND SHIFT...SO RAISED LOWS A COUPLE OF DEGREES. 

UPPER LOW WL DRIFT SLOWLY EWD ACRS NRN MO ON TUES AND THIS WL CONT 
TO BRING A CHC OF PRECIP MAINLY ACRS SERN CWA ON TUES WITH BEST CHC 
ACRS NW IA. SO WL KEEP CAT POPS THERE AND GO DRY W OF I29 TUES. 
TEMPS ALOFT MARGINAL FOR ANY SNOW...BUT WL KEEP CHC OF A R/S MIXTURE 
ON WRN EDGE OF PRECIP TUES MORN. CLOUD COVER WILL PERSIST MOST OF 
DAY E OF I29 WITH MORE SUN ACRS THE WEST. SO WUD EXPECT WRN CWA TO 
BE WARMER WITH HIGHS FM 45 TO 50 WITH 40 TO 45 EAST.

WL CLR OUT FOR A TIME TUES NITE ERN CWA AS LOW PULLS AWAY...BUT WL 
CLOUD BACK UP AGAIN FM THE NW AS S/W DROPS SEWD OUT OF ND. MOISTURE 
WL BE SOMEWHAT LACKING WITH THIS SYS...HWVR WITH VERY COLD AIR ALOFT 
ASSOCD WITH THIS FEATURE...WUD NOT BE SURPRISED TO GET CONVECTIVE 
SNOW SHOWERS OUT OF THIS WAVE ESPEC ACRS ERN CWA WITH FLURRIES TO 
THE WEST LATE TUES NITE INTO WED EVE. TEMPS WL BE ABOUT 10 DEG 
COLDER ON WED THAN TUES AND ALSO WINDY AS MIXING SHUD BRING GUSTIER 
WINDS ALOFT DOWN TO SFC. 

SHUD BE A DRY BUT COOL THANKSGIVING AS SFC HIGH PUSHES E ACRS THE 
DAKOTAS. WNDS MAY BE STILL A BIT GUSTY IN THE MORN AND TAPER OFF IN 
THE AFTN. WITH PLENTY OF SUN EXPECTED...TEMPS SHUD BE NEAR OR 
SLIGHTLY ABOVE NORM.

PREFER THE EC SOLUTION IN THE EXTENED AND THE 12Z GFS HAS COME 
AROUND TO THIS SOLUTION. THIS WUD INDICATE THAT FRI SHUD WARM INTO 
THE 40S AND 50S AHEAD OF NEXT CDFNT THAT WL DROP SEWD ACRS CWA ON 
SAT. SO BUMPED UP TEMPS A FEW DEG FOR FRI AND ONLY SLIGHTLY COOLER 
ON SAT. MAIN SURGE OF COLDER AIR WL LIKELY LAG BEHIND FNT ON SAT AND 
MIXING WL ALLOW TEMPS TO RISE INTO 40S. UPPER LOW DROPPING SWD OUT 
OF ND ON SUN WL PBLY PRODUCE A FEW FLURRIES OR SCT SW- AND DID THROW 
A 20% INTO FCST ALONG WITH COLDER TEMPS.   

&&

.AVIATION...
MVFR CONDITIONS TO CONTINUE THROUGH THE NIGHT ACROSS THE EASTERN 
HALF OF THE CWA...WITH IMPROVING CONDITIONS IN THE WESTERN HALF 
THROUGH THE EVENING. A BAND OF RAIN WILL FILL IN ACROSS NORTHWEST 
IOWA AND EXTREME SOUTHEAST SD...THEN PROGRESS EAST THROUGH THE 
NIGHT. 



&&

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

$$