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. && $$