824 
FXUS63 KFSD 140850
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
348 AM CDT TUE AUG 14 2012

.DISCUSSION.../ISSUED AT 348 AM CDT/
YET ANOTHER PLEASANT SUMMER DAY EXPECTED ACROSS THE REGION TODAY 
WITH SURFACE HIGH PRESSURE SLIPPING SOUTHEASTWARD INTO THE MID 
MISSISSIPPI VALLEY BY THIS AFTERNOON.  RETURN FLOW BEHIND THE HIGH 
WILL BRING INCREASED SOUTHERLY FLOW...WHICH WILL BE GREATEST ACROSS 
OUR WESTERN HALF. WINDS SHOULD BECOME BREEZY INTO THE JAMES VALLEY 
AND WESTWARD. HIGHS WILL BE WARMER TODAY THAN IN PREVIOUS DAYS WITH 
HIGHS MAINLY IN THE 80S...TO AROUND 90 IN SOUTH CENTRAL SOUTH 
DAKOTA.

LOW LEVEL JET IS EXPECTED TO START KICKING IN THIS EVENING AND 
OVERNIGHT ACROSS CENTRAL AND EASTERN PORTIONS OF THE FORECAST AREA. 
THIS WILL BE COUPLED WITH A WEAK MID LEVEL WAVE WHICH TRACKS EAST 
SOUTHEAST THROUGH THE FORECAST AREA. THIS SHOULD BE ENOUGH TO SQUEAK 
OUT SOME ISOLATED THUNDERSTORMS...ALTHOUGH THE MEAGER MOISTURE COULD 
WILL KEEP PRECIPITATION AMOUNTS WELL IN CHECK. 

A BROAD CANADIAN UPPER TROUGH DIGGING INTO THE NORTHERN PLAINS WILL 
DROP A FAIRLY POTENT COLD FRONT ACROSS THE NORTHERN PLAINS ON 
WEDNESDAY. MIXY SOUTH SOUTHWEST WINDS AHEAD OF THE FRONT WILL USHER 
IN THE WARMEST DAY OF THE WEEK AHEAD OF THE FRONT...WITH HIGHS IN 
THE UPPER 80S TO MID 90S. THE FRONT WILL TRACK THROUGH THE FORECAST 
AREA WEDNESDAY AFTERNOON AND EVENING...ACCOMPANIED BY A STRONG MID 
LEVEL WAVE A FRONTOGENESIS. CAPPING SHOULD HOLD OFF INITIAL 
CONVECTION IN OUR FAR WESTERN COUNTIES EARLY IN THE DAY...HOWEVER 
WILL LIKELY SEE SCATTERED STORMS START FIRING EAST OF A YANKTON TO 
BROOKINGS LINE IN THE LATE AFTERNOON AND BECOME MORE LIKELY ACROSS 
NORTHWEST IOWA AND SOUTHWEST MINNESOTA IN THE EVENING HOURS AS 
DAYTIME HEATING PEAKS AND THE 850 MB WAVE/FRONT DIGS INTO THE AREA. 
STEEP LAPSE RATES APPROACHING 10C/KM...1500+ J/KG CAPE AND 40 KT 
BULK SHEAR PER NAM FORECAST SOUNDINGS SUGGEST THE POTENTIAL FOR SOME 
SEVERE STORMS WITH HAIL AND WIND CONCERNS...ALTHOUGH LOWER LEVEL 
MOISTURE DOES APPEAR SOMEWHAT LACKING. WILL CONTINUE WITH LIKELY TO 
CATEGORICAL POPS WEDNESDAY EVENING ACROSS NORTHWEST IOWA AND 
SOUTHWEST MINNESOTA.

DRY NORTHWEST FLOW SETTLES IN FOR THE LATER HALF OF THE WEEK. 
TEMPERATURES WILL BE QUITE A BIT COOLER ON THURSDAY WITH BREEZY 
NORTHERLY WINDS ADVECTING IN SOME BELOW NORMAL TEMPERATURES AND 
CLOUDS DECREASING THROUGH THE MORNING.  HIGHS WILL LIKELY ONLY BE IN 
THE 70S ON THURSDAY AND FRIDAY...BUT WILL BE ON A GRADUAL WARMING 
TREND THROUGH THE WEEKEND.  OVERALL CONDITIONS LOOK PRETTY DRY WITH 
ONLY SOME MINOR MOISTURE STARVED WAVES TRACKING THROUGH THE PLAINS 
IN THE NORTHWEST FLOW. GFS PAINTS SOME LIGHT POPS ACROSS THE AREA 
AROUND THE SATURDAY TIME FRAME...WHICH IS NOT WELL SUPPORTED IN THE 
OTHER MODELS. WILL CONTINUE TO LEAVE OUT ANY MENTION OF POPS BEYOND 
EARLY THURSDAY WITH LITTLE CONFIDENCE IN THE TIMING AND TRACK OF ANY 
MID LEVEL WAVE THAT DOES MAKE AN APPEARANCE. 


&&

.AVIATION.../FOR THE 06Z TAF ISSUANCE/
THE 06Z TAFS REFLECT VFR CONDITIONS THROUGH THE REST OF TONIGHT AND 
TUESDAY WITH A COUPLE OF CAVEATS. WITH LIGHT WINDS ONCE AGAIN 
DEVELOPING AND SMALL DEW POINT DEPRESSIONS...ESPECIALLY EAST OF THE 
JAMES RIVER VALLEY...THERE IS A CHANCE FOR IFR AND LIFR RADIATIONAL 
FOG EAST OF THE JAMES. HOWEVER AT THIS TIME WE DID NOT REDUCE THE 
VISIBILITIES IN THE KFSD AND KSUX TAF SITES AS THE EXACT SPOTS OF 
FOG DEVELOPMENT ARE VERY DIFFICULT TO PREDICT FOR TONIGHT. BUT IT IS 
SOMETHING TO WATCH FOR. AT THIS TIME...IT APPEARS THAT THE WESTERN 
PLAINS CONVECTION MAY STAY WEST OF THE SIOUX FALLS FORECAST AREA 
LATE TONIGHT. HOWEVER FOR TUESDAY EVENING...ANOTHER MID LEVEL 
DISTURBANCE COUPLED WITH A FAIRLY STRONG LOW LEVEL JET AND WARM AIR 
ADVECTION...SHOULD PRODUCE A FEW THUNDERSTORMS ALONG AND WEST OF I 
29 IN OUR SOUTH DAKOTA ZONES. THIS WAS REFLECTED WITH A TEMPO GROUP 
IN THE KHON TAF. BUT CONFIDENCE IS TOO LOW TO MENTION IN THE KFSD 
TAF RIGHT NOW. 

&&

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

&&

$$