675 FXUS63 KFSD 271213 AFDFSD AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SIOUX FALLS SD 713 AM CDT MON JUL 27 2015 .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 417 AM CDT MON JUL 27 2015 STATE OF THE REGION IN THE WEE HOURS OF THE MORNING REVEALS A COUPLE AREAS OF CONVECTION ONGOING. THE FIRST IS ACROSS NORTH CENTRAL SOUTH DAKOTA WITH A SOUTHWARD TAIL...ASSOCIATED WITH LEADING WEAK WAVE LIFTING OVER RIDGE INTO NORTH DAKOTA...AND THE LEADING LOW LEVEL JET INCREASE THROUGH CENTRAL SD. WILL BE A CLOSE CALL...BUT WILL LIKELY FIND AN ISOLATED SHOWER/THUNDERSTORM BRUSH AREAS AROUND KHON IN THE PREDAWN HOURS. SECOND AREAS OF CONVECTION IS A BROAD MASS OF THUNDERSTORMS ACROSS KANSAS AND EXTENDING NORTHWARD INTO NEBRASKA... THE NORTHERN EXTENT OF WHICH REMAINS MORE ACTIVE AT TIMES TOWARD NORTHEAST NEBRASKA. AS WAVE MOVES EASTWARD THROUGH THE CENTRAL PLAINS...LIKELY TO SEE AT LEAST ISOLATED CONVECTION PUSHING THROUGH THE LOWER MISSOURI VALLEY INTO NORTHWEST IOWA DURING THE EARLY TO MID MORNING HOURS...ON THE LEADING GRADIENT OF STEEPENING MID LEVEL LAPSE RATES. FAIRLY MODIFIED AIRMASS TO THE SOUTH WILL BE A STRUGGLE TO DESTABILIZE GREATLY FOR A GOOD PORTION OF THE DAY...AND WILL ALSO LIKELY BE BETWEEN WEAK SYSTEMS DURING THIS TIME...SO ELIMINATED A GREAT DEAL OF THE LOWER POPS THROUGH THE MIDDLE PORTIONS OF THE DAY. SOME OF THE LATEST HIGH RESOLUTION MODELS INDICATE THIS TREND OF LESSER ACTIVITY AFTER DWINDLING OF MORNING ACTION...AND HARD TO ARGUE WITH LACK OF BOUNDARIES AND DELAY TO DESTABILIZING. ANY SIGNIFICANT SURFACE OR NEAR SURFACE BOUNDARY WILL REMAIN WELL WEST AND SOUTH THROUGH THE AFTERNOON...BUT DISCONTINUITY SHOULD BE WORKING NORTHWARD TROUGH NEBRASKA...AND LOW PROBABILITY TO IGNITE A FEW STORMS FAR WEST AND MISSOURI VALLEY LATE DAY. OVERALL...BEST DYNAMICAL FORCING LOOKS TO REMAIN WEST OF THE AREA THROUGH THE DAY AND EVEN INTO EARLY EVENING...AND WILL LIKELY IGNITE CONVECTION NEAR DEVELOPING DRYLINE/COLD FRONT IN THE HIGH PLAINS LATE AFTERNOON. MODELS APPEAR TO BE A BIT OVERZEALOUS IN INSTABILITY AND WEAKENING WHAT SHOULD BE A FORMIDABLE CAP OVER THE AREA THIS AFTERNOON. GREATEST WEAKENING OF THE CAP WOULD OCCUR IN BETTER HEATING AXIS IN THE FAR WESTERN CWA...WHERE INCREASING MOISTURE TRANSPORT THROUGH THE DAY AND ADVECTION OF ELEVATED MIXED LAYER WOULD PERHAPS BRING UP TO 2000 J/KG MLCAPE...STILL WEAKLY CAPPED BY PEAK HEATING. LOW LEVEL JET WILL INCREASE THROUGH THE DAY...AND BY THE EVENING INCREASE SHOULD REACH 45 TO 55 KNOTS. BEST CONVERGENCE FROM FEATURE WILL ALSO FAVOR AREAS NORTH OF THE CWA. DEEP SHEAR WILL BECOME IMPRESSIVE...BUT STRONGEST VALUES LAGGING TO THE WEST. ENOUGH FOR ORGANIZATION...LIKELY MORE TOWARD THE LINEAR SIDE BY THE TIME ANYTHING PROGRESSES EASTWARD...BUT WOULD NOT COUNT OUT A SLIGHTLY ELEVATED SUPERCELL ONCE LOW LEVEL JET REALLY KICKS IN BY LATE EVENING. OVERALL...SET UP IS ONE WHERE IF STORMS FORM...THEY DO PRESENT A DECENT PROBABILITY OF SEVERE STORMS...WITH BEST SEVERE CHANCES NORTH AND WEST IN THE CWA...AND MAINLY A HAIL/WIND THREAT DURING THE LATTER EVENING AND OVERNIGHT. VERY WARM AND HUMID CONDITIONS TODAY WILL SEE THE HEAT INDEX NUDGE 100 DEGREES AT TIMES THIS AFTERNOON FOR SPOTTY LOCATIONS THROUGH THE MISSOURI AND JAMES VALLEYS...BUT NEITHER WIDESPREAD ENOUGH OR PERSISTENT ENOUGH TO WARRANT ISSUING A HEAT ADVISORY. NONETHELESS... WORTHY OF CAUTION TO AVOID OVEREXERTION IN THE HOT CONDITIONS. IMPRESSIVE UPPER WAVE MOVING OUT OF THE NORTHERN ROCKIES TONIGHT WILL PUSH COLD FRONT EASTWARD. CONVECTION ALONG THIS BOUNDARY MAY START TO LOSE COHESION WORKING EASTWARD INTO A WARMER LAYER ALOFT... ESPECIALLY EROSIVE TOWARD THE SOUTH LATER IN THE NIGHT. BOUNDARY SHOULD PUSH JUST EAST OF JAMES VALLEY BY 12Z. AHEAD OF THE FRONT... REMAINING VERY WARM...BREEZY AND HUMID...WITH SHARP DRYING BEHIND. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 417 AM CDT MON JUL 27 2015 AN UNSEASONABLY STRONG WAVE MOVING THROUGH TUESDAY...COMING A LITTLE FASTER THAN WAS SUGGESTED YESTERDAY. THIS DROPS THE THREAT OF VERY HOT AND HUMID CONDITIONS AHEAD OF THE FRONT SINCE THE BOUNDARY SHOULD BE OUT OF THE CWA BY ABOUT 18Z TO 21Z. AREAS FROM WINDOM TO SPENCER IOWA TO IDA GROVE COULD SEE SOME UPPER 90 HEAT INDICES BUT THAT HEAT WILL GET QUICKLY FLUSHED OUT IN THE EVENING WHEN THE STRONG COOL/DRY FRONT SWINGS THROUGH. THE REMAINDER OF THE CWA WILL SEE DEW POINTS TANK THROUGH THE DAY AND THE WESTERN CWA MAY EVEN SEE SOME DEW POINTS INTO THE 30S. A FAIRLY GUSTY NORTHWEST WIND AND TEMPERATURES IN THE 80S IS EXPECTED. THE MODELS HINTING AT SOME COOLER AIR WRAPPING SOUTH INTO THE CWA TUESDAY NIGHT WHICH WOULD KEEP THE WIND UP THROUGH THE NIGHT. BUT DRY AND MILD WITH LOW IN THE UPPER 50S TO LOWER 60S. WEDNESDAY WILL BE A DRY...MIXY AND WARM DAY WITH HIGHS TOPPING OUT IN THE LOWER TO MIDDLE 80S. IN THE OUTER PERIODS(THURSDAY THROUGH SUNDAY)...FAIRLY FAST WEST TO NORTHWEST FLOW ALOFT THROUGH THE ENTIRE PERIOD. THIS PATTERN SHOULD SUPPORT LESS HUMIDITY AND LOWER CHANCES FOR THUNDERSTORMS SO ONLY SOME SPOTTY SLIGHT CHANCES AT THIS TIME. AT THIS TIME THE BEST CHANCE APPEARS TO BE ON SATURDAY NIGHT AS A LITTLE JET ACCELERATION DROPS SOUTH INTO THE GREAT LAKES REGION AND IS EXPECTED TO SWING A WEAK BOUNDARY INTO THE AREA. OVERALL A DECENT STRETCH OF WEATHER WITH HIGHS IN THE 80S AND LOWS IN THE 60S. SATURDAY COULD PROVE TO BE A BIT WARMER IF THE BOUNDARY SNEAKS IN FROM THE NORTH AT JUST THE RIGHT TIME TO ALLOW FOR SOME ENHANCED WARMING AHEAD OF THE FRONT. IF THE TIMING IS RIGHT WOULD NOT BE SURPRISED TO SEE HIGHS SATURDAY WELL IN THE 90S IN SOME LOCATIONS. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING) ISSUED AT 710 AM CDT MON JUL 27 2015 SCATTERED CONVECTION PUSHING NORTHEAST ACROSS THE AREA THIS MORNING...WITH BRIEF MVFR VISIBILITY. OTHER PATCHY MVFR TO IFR CEILINGS STREAMING ACROSS THE AREA FROM THE EAST...AND SHOULD GRADUALLY WORK TOWARD MORE SCATTERED BY LATE MORNING. CONFIDENCE IN ANY FEATURE IS FAIRLY LOW PAST MORNING CONVECTION AND CLOUDS. HAVE NOT INCLUDED ANY CONVECTION LATER INTO THE NIGHT OTHER THAN A BRIEF CHANCE AT KHON...AS CONFIDENCE IS LOW ON TIMING. HOWEVER...ANY STORMS THAT DO FORM WILL HAVE POTENTIAL TO BE SEVERE. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...CHAPMAN LONG TERM...08 AVIATION...CHAPMAN