108 FXUS63 KFSD 201732 AFDFSD AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SIOUX FALLS SD 1232 PM CDT SUN JUL 20 2014 .SHORT TERM...(TODAY AND TONIGHT) ISSUED AT 351 AM CDT SUN JUL 20 2014 DEVELOPMENT OF STRATOCU IN EASTERN PORTIONS OF THE AREA YESTERDAY PUT A DAMPER ON EXPECTED WARMING. MODELS SHOWING THAT LOW LEVEL MOISTURE STILL HANGING AROUND ACROSS THE EAST TODAY BENEATH THE INVERSION...THOUGH NOT VERY DEEP ON FORECAST SOUNDINGS. EXPECT WE WILL SEE SOME DEVELOPMENT AGAIN TODAY...THOUGH AT THIS POINT DO NOT ANTICIPATE COVERAGE TO BE AS EXTENSIVE AS YESTERDAY AND THUS LOWER TO MID 80S SHOULD BE ATTAINABLE FOR HIGHS NEAR/EAST OF I-29. AREAS ALONG/WEST OF THE JAMES SEE MORE NOTABLE LOW LEVEL WARMING AND WILL STICK WITH IDEA OF LOWER-MID 90S FOR HIGHS IN THIS AREA. THIS NEAR THE WARMEST GUIDANCE SOLUTIONS...WITH SOME OF THE GLOBAL MODELS AND NUMERICAL GUIDANCE A FEW DEGREES LOWER. WITH FORECAST DEW POINTS IN THE UPPER 60S TO AROUND 70...LOCATIONS IN OUR WEST DO BRUSH TRIPLE DIGIT HEAT INDICES FOR 2-3 HOURS THIS AFTERNOON. HOWEVER WITH SMOKE LAYER ALOFT STILL EXPECTED TO BE FAIRLY WIDESPREAD...THIS COULD HOLD TEMPS DOWN A BIT FROM FULL MIXING POTENTIAL...AND THUS HAVE OPTED TO HOLD OFF ON ISSUING HEAT ADVISORY IN OUR WEST AT THIS TIME. WILL BE SOMETHING FOR DAY SHIFT TO MONITOR THOUGH. OTHER QUESTION FOR THE LATE AFTERNOON/EVENING IS WHETHER BOUNDARY WILL SAG FAR ENOUGH SOUTHEAST TO ALLOW ISOLATED STORMS TO BRUSH OUR NORTHWEST CWA. MOST GUIDANCE HOLDS THE BOUNDARY WELL NORTH OF THE AREA...WITH STRONG CAP KEEPING OUR AREA DRY THROUGH TONIGHT. HOWEVER HI-RES ARW AND RAP/HRRR MORE AGGRESSIVE IN DROPPING THE BOUNDARY FARTHER SOUTH AND DEVELOPING CONVECTION INTO OUR NORTHWEST CORNER BY EVENING. SIDING WITH THE NORTHERN/DRY SOLUTION FOR NOW...BUT AGAIN WILL BE SOMETHING TO WATCH THROUGH THE DAY. .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 351 AM CDT SUN JUL 20 2014 PRIMARY FOCUS IN THE MEDIUM RANGE AND EXTENDED PORTIONS OF THE FORECAST REMAINS ON HOT AND HUMID CONDITIONS OF MONDAY...ALONG WITH SEVERE WEATHER POTENTIAL MONDAY NIGHT. ON MONDAY...INCREASING MID-LEVEL HEIGHTS AND SIGNIFICANT NORTHWARD ADVECTION OF BOUNDARY LAYER MOISTURE WILL WORK IN TANDEM TO PRODUCE A RAPID SHIFT FROM SEASONALLY COOL CONDITIONS OF THE PAST WEEK TO A BRIEF STINT OF DANGEROUS HEAT. AS A MID-LEVEL SHORTWAVE ROTATES AROUND THE WESTERN FLANK OF THE MID-LEVEL RIDGE...SURFACE CYCLOGENESIS WILL OCCUR OVER WEST CENTRAL SOUTH DAKOTA EARLY MONDAY MORNING. A WARM FRONT IS EXPECTED TO FORM NORTH OF THE CWA WITH THE INCREASED MERIDIONAL FLOW ALLOWING MOISTURE TO POOL SOUTH OF THE BOUNDARY MONDAY AFTERNOON. ADJUSTING RAW MODEL DEW POINTS NEAR 80F...BY TAKING ACCOUNT OF SLIGHT DOWNWARD MIXING OF DRIER AIR ALOFT...SHOULD STILL RESULT IN DEW POINT VALUES 74-78 OVER MUCH OF THE CWA. ALOFT...H850 TEMPERATURES APPROACHING +30C SHOULD MOVE OVERHEAD...EFFECTIVELY CAPPING THE CWA THROUGH THE AFTERNOON. TEMPERATURES WILL RISE AROUND THE 90 DEGREE MARK IN AREAS ALONG AND EAST OF I-29...WITH READINGS PUSHING 100 DEGREES WEST OF THE JAMES RIVER. GIVEN THE RECENT COOL SPELL...THE ABSENCE OF ANY SIGNIFICANT HEAT THIS SUMMER SEASON...AND THE DEGREE OF HUMIDITY THAT WILL BE PRESENT MONDAY AFTERNOON...THE POTENTIAL IMPACTS FROM A SHORT DURATION SPELL OF HEAT COULD BE AMPLIFIED. THUS...WILL GO AHEAD AND ISSUE A HEAT ADVISORY A BIT EARLY AND AHEAD OF THE NEW WORK WEEK. REGARDING CONVECTION CHANCES MONDAY NIGHT...STRONG SIGNALS CONTINUE TO PERSIST THAT SEVERE CONVECTION WILL FORM EARLY MONDAY AFTERNOON ACROSS NERN SD AND SOUTHERN ND AS LARGE SCALE LIFT FROM AN APPROACHING SHORTWAVE REACHES THE REGION. THE MAJORITY OF THIS ACTIVITY SHOULD STAY NORTH OF THE CWA THROUGH THE AFTERNOON. THE CONCERNS HOWEVER WOULD BE THE POTENTIAL THAT ONCE A WELL DEFINED COLD POOL FORMS...SEVERAL OF THESE CLUSTERS COULD BEGIN TO TAKE A TURN TO THE SOUTH AND SOUTHEAST MONDAY EVENING. CORFIDI VECTORS BY 03Z SHOW INCREASED POTENTIAL FOR A SHIFT SOUTHEAST WHICH COULD BRING THE TAIL-END OF THIS ACTIVITY ACROSS THE NORTHEASTERN THIRD OF THE CWA. THE PRIMARY RISKS WOULD BE DAMAGING WINDS. A COLD FRONT WILL PASS THROUGH THE CWA EARLY TUESDAY MORNING...AND THIS WILL LEAD TO SLIGHTLY COOLER TEMPERATURES. TEMPERATURES WILL RUN NEAR THE SEASONAL NORMAL WEDNESDAY AND THURSDAY...BEFORE A STRONG UPPER LOW EJECTS EASTWARD FROM BRITISH COLUMBIA. THE GFS REMAINS A STRONG AND FURTHER SOUTH OUTLIER THAN THE EC/GEM...AND THUS WILL NOT GO QUITE AS BULLISH WITH POPS ON THUR/FRI...BUT CONTINUE TO ADVERTISE LOW CHC POPS. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 1230 PM CDT SUN JUL 20 2014 AREA OF MVFR STRATOCU AGAIN OUT THERE THIS AFTERNOON. LOOKS LIKELY THAT KFSD WILL STAY MVFR THROUGH THE DAY. KSUX REMAINS RIGHT ON THE EDGE OF THE STRATOCU. AS MIXING CONTINUES WE MAY SEE THE CLOUD COVER EXPAND SOMEWHAT TO THE EAST...THUS KSUX WILL PROBABLY END UP SCATTERED TO BROKEN THROUGH THE AFTERNOON AROUND 2500 FEET. CLOUDS WILL PROBABLY DISSIPATE AFTER SUNSET...WITH CONDITIONS BECOMING VFR. HOWEVER SIGNS IN THE MODELS THAT LOW STRATUS WILL FORM OVERHEAD LATE TONIGHT INTO EARLY TOMORROW...THUS ADDED THIS INTO ALL THREE TAFS. THIS STATUS MAY INITIALLY BE IFR...WITH A SLOW INCREASE INTO THE MVFR THROUGH THE MORNING. HOWEVER...LOOKING LIKE MVFR CONDITIONS MAY VERY WELL LINGER INTO AT LEAST A PORTION OF THE AFTERNOON HOURS EAST OF THE JAMES RIVER. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR SDZ038>040-050- 052>071. MN...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR MNZ071-072-080- 081-089-090-097-098. IA...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR IAZ001>003- 012>014-020>022-031-032. NE...HEAT ADVISORY FROM 11 AM TO 9 PM CDT MONDAY FOR NEZ013-014. && $$ SHORT TERM...JH LONG TERM...DUX AVIATION...CHENARD