749 FXUS63 KFSD 221158 AFDFSD AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SIOUX FALLS SD 652 AM CDT FRI AUG 22 2014 .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 406 AM CDT FRI AUG 22 2014 MAIN FOCUS IN THE SHORT TERM WILL BE A FAIRLY POTENT WAVE EXPECTED TO IMPACT THE FORECAST AREA BEGINNING THIS EVENING. LARGE TROUGH OVER THE INTERMOUNTAIN WEST THIS MORNING WILL EJECT A SHORTWAVE FROM THE FOUR CORNERS REGION INTO THE CENTRAL HIGH PLAINS THIS AFTERNOON. MEANWHILE SURFACE LOW PRESSURE DEEPENS IN WESTERN KANSAS AND LIFTS NORTHWARD INTO NEBRASKA IN THE EVENING. AN ATTENDANT WARM FRONT WILL ALSO LIFT NORTHWARD TOWARDS THE MISSOURI VALLEY LATE TONIGHT. MUGGY CONDITIONS WILL PERSIST TODAY...WITH MID TO UPPER 60S DEWPOINTS INCREASING THROUGH THE DAY TODAY AS FLOW CONTINUES TO TAP INTO MOISTURE. EXPECT DEWPOINTS WELL INTO THE LOW OR MID 70S ACROSS OUR SOUTHEASTERN HALF BY THIS AFTERNOON. WITH HIGH TEMPERATURES WARMING ONCE AGAIN INTO THE 80S...HEAT INDEX VALUES WILL REACH THE MID TO UPPER 90S IN PARTS OF NORTHWEST IOWA AND FAR SOUTHEAST SOUTH DAKOTA. COULD SEE A FEW INITIAL HIGH BASED CONVECTION FIRE EARLIER IN THE DAY IN NEBRASKA AND CLIP OUR SOUTHERN BORDER. HOWEVER...LATER THIS EVENING AS THE LOW LEVEL JET BEGINS INCREASING AND THE FRONT STARTS LIFTING NORTHWARD...CONVECTION WILL SLOWLY BUILD NORTHWARD INTO THE MISSOURI VALLEY...BECOMING CATEGORICAL ACROSS OUR SOUTHWESTERN HALF OVERNIGHT. MAIN CHANGE WAS TO SLOW DOWN THE TIMING SEVERAL HOURS WITH NEARLY EVERY MODEL SUPPORTING A SLOWER PROGRESSION OF THE BOUNDARY LIFTING NORTH. STRONG INSTABILITY ESPECIALLY IN OUR SOUTH COULD BUMP CAPE VALUES TO 2500 J/KG...WITH INITIAL MEAGER SHEAR INCREASING OVERNIGHT AS THE LLJ INCREASES. A FEW ISOLATED EMBEDDED SEVERE STORMS WILL BE POSSIBLE LATE TONIGHT NEAR THE MISSOURI VALLEY AS THE FRONT NEARS THE AREA...HOWEVER THE BULK OF THE THREAT WILL REMAIN SOUTH OF THE CWA. MAIN SEVERE THREAT WOULD BE MARGINAL HAIL AND GUSTS TO 65 MPH. LOWS TONIGHT WILL BE IN THE MID 60S TO NEAR 70. .LONG TERM...(SATURDAY THROUGH THURSDAY) ISSUED AT 406 AM CDT FRI AUG 22 2014 IN GENERAL...00Z GFS RUN IS MUCH MORE PROGRESSIVE THAN THE OTHER SOLUTIONS...AND GIVEN ITS OUTLYING SOLUTION...HAVE DISCOUNTED IT AND HAVE ATTEMPTED TO REDUCE THE BLENDS INFLUENCE. WARM AND MUGGY PATTERN CONTINUES THIS WEEKEND AHEAD OF A SLOW MOVING TROUGH MOVING OUT OF THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES. LEADING SHORTWAVE LIFTING INTO THE REGION IN SOUTHWEST FLOW APPEARS TO MAINLY BE FOCUSED WEST...AND WHILE THE EAST REMAINS UNSTABLE...LACK OF FORCING AND STRONG ENOUGH CAP SHOULD LIMIT CONVECTION SPREADING EAST. AS SUCH...HAVE SCALED BACK POPS EAST OF I-29 THROUGHOUT THE DAY ON SATURDAY. AS PREVIOUS FORECAST MENTIONED...PWAT VALUES ARE NEAR 2 INCHES...WHICH IS AROUND 2 STANDARD DEVIATIONS ABOVE NORMAL. WITH STRONG WARM AIR ADVECTION THROUGHOUT THE DAY SATURDAY...THERE IS THE POTENTIAL FOR REGENERATING CELLS ALONG THE WARM FRONT LIFTING NORTH THROUGH THE AREA. CLOSER TO THE CENTER OF THE SHORT WAVE...CLOUDS AND CONVECTION WILL KEEP TEMPERATURES DOWN...WHILE FURTHER TO THE EAST TEMPERATURES WILL APPROACH 90. ON SATURDAY NIGHT INTO SUNDAY...UPPER LOW APPROACHES FROM THE WEST BUT RIDGE TO THE EAST IS FAIRLY STRONG SO THE LOW LIFTS MORE NORTH THAN TRANSLATING EAST. WITH THE FOCUS FURTHER TO THE WEST...HAVE CUT POPS BACK SOME ESPECIALLY THROUGHOUT THE DAY ON SUNDAY. COLD FRONT MOVES THROUGH ON SUNDAY WITH MUCH COOLER AND DRIER AIR WORKING INTO THE REGION BEHIND THE FRONT. TEMPERATURES APPEAR TO REMAIN BELOW NORMAL THROUGH THE BETTER PORTION OF NEXT WEEK...WITH THE BEST CHANCE OF PRECIPITATION ON WEDNESDAY AS WEAK UPPER LEVEL TROUGH MIGRATES THROUGH THE AREA. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY NIGHT) ISSUED AT 652 AM CDT THU AUG 21 2014 PATCHY SHALLOW FOG EARLY THIS MORNING WILL QUICKLY LIFT BY 13Z...WITH VFR CONDITIONS EXPECTED THROUGH 00Z. CONVECTION LIKELY TO DEVELOP THIS EVENING NEAR THE MISSOURI RIVER AND VERY SLOWLY LIFT NORTHEAST THROUGH THE END OF THE TAF PERIOD. MVFR AND IFR VISIBILITY AND CEILINGS WILL BE POSSIBLE IN THUNDERSTORMS WITH HEAVY RAINS. EXPECT ACTIVITY IN KSUX AFTER 03Z...POSSIBLE MAKING IT AS FAR NORTH AS KFSD AND KHON AFTER 06Z. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM... LONG TERM... AVIATION...