945
FXUS63 KFSD 161128
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
628 AM CDT TUE JUL 16 2019
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 308 AM CDT TUE JUL 16 2019
EARLY THIS MORNING, WATCHING A LINE OF ELEVATED THUNDERSTORMS
MOVING ACROSS SOUTHERN SD/NORTHERN NE. SEVERE THREAT APPEARS
MARGINAL AS STORMS MOVE INTO A VERY WARM WEAK SHEAR ENVIRONMENT.
CANNOT COMPLETELY RULE OUT SOME SMALL HAIL, BUT BIGGER THREAT WILL
BE WIND. REGIONAL OBSERVATIONS EARLIER THIS MORNING PEAKED
BETWEEN 45 AND 55 MPH ACROSS NORTHERN NE, BUT MORE RECENT REPORTS
SHOW STORM INDUCED WINDS GENERALLY 40 MPH OR LESS. THIS MCS WILL
MOVE SLOWLY TO THE EAST THROUGH THE MORNING AND OUT OF THE AREA
NO LATER THAN NOON.
BEST CHANCES FOR CONVECTIVE RE-DEVELOPMENT THIS AFTERNOON WILL BE
ACROSS SOUTHERN MN INTO IA AS NOTED BY THE DAY 1 SPC CONVECTIVE
OUTLOOK. IT IS IN THIS AREA WHERE A MCV FROM THIS MORNING'S
CONVECTION MAY INTERACT WITH A RESIDUAL SURFACE BOUNDARY LEFT FROM
THUNDERSTORMS THAT MOVED MAINLY ACROSS CENTRAL/SOUTHERN MN LAST
EVENING. SHEAR LOOKS GOOD ENOUGH FOR AT LEAST A FEW MARGINALLY
STRONG/SEVERE STORMS, SO SOMETHING TO WATCH THROUGH THE DAY.
TEMPERATURES TODAY WILL BE A BIT COOLER THAN YESTERDAY WITH HIGHS
IN THE MID 80S TO NEAR 90 DEGREES, BUT IT WILL STILL FEEL MUGGY
WITH DEWPOINTS IN THE 70S.
MORE CONCERNED ABOUT SEVERE THREAT LATE THIS EVENING AND OVERNIGHT
AS A STRONGER SHORT-WAVE MOVES THROUGH QUASI-ZONAL FLOW ALOFT.
UNLIKE THIS MORNING, DEEP SHEAR IS STRONGER WITH A 300 HPA 50-60
KT JET MAX MOVING ACROSS THE FORECAST AREA. 0-3 KM SHEAR ALSO
INCREASES TO NEAR 30 KTS AND MODEL HODOGRAPHS SHOW DECENT CURVATURE
IN THE LOWEST KILOMETER. WITH AMPLE INSTABILITY, LATEST HIGH
RESOLUTION CAMS SUGGEST ANOTHER LINE OF STRONGER THUNDERSTORMS
WILL MOVE ACROSS THE FORECAST AREA OVERNIGHT. SPC DAY 1 OUTLOOK
SHOWING A SLIGHT SEVERE RISK FOR AREAS WEST OF THE JAMES RIVER
SEEMS REASONABLE AT THIS TIME. PRIMARY THREATS WITH THESE STORMS
WILL BE LARGE HAIL UP TO PING PONG SIZE AND DAMAGING WINDS IN
EXCESS OF 70 MPH.
LONG TERM
(WEDNESDAY THROUGH MONDAY)
ISSUED AT 308 AM CDT TUE JUL 16 2019
BIG STORY WEDNESDAY THROUGH FRIDAY WILL BE CONTINUED HIGH HEAT,
ESPECIALLY FOR AREAS SOUTH OF I-90. DAILY HIGHS IN THE LOWER TO
MID 90S COMBINED WITH DEWPOINTS INTO THE MID 70S WILL RESULT IN
HEAT INDICES OVER 100 DEGREES. FOR THIS REASON, WILL CONTINUE
WITH AN EXCESSIVE HEAT WATCH WEDNESDAY AFTERNOON THROUGH FRIDAY.
THUNDERSTORM CHANCES CONTINUE WEDNESDAY WITH A DRYING TREND
LOOKING MORE LIKELY THURSDAY INTO FRIDAY. MUCH OF WHAT HAPPENS
WEDNESDAY WILL DEPEND ON THE EVOLUTION OF TONIGHT'S MCS, BUT THE
OVERALL ENVIRONMENT WOULD CONTINUE TO SUPPORT STRONG TO SEVERE
STORMS FOR PARTS OF THE AREA.
SATURDAY IN SUNDAY, 00Z GFS/ECMWF SHOW THE STRONG 500 HPA RIDGE
BREAKING DOWN A BIT AS A LARGER AND STRONGER SHORT-WAVE SWEEPS
ACROSS THE NORTHERN PLAINS. THAT SAID, THE GFS IS MORE AGGRESSIVE
WITH THIS IDEA THAN THE ECMWF, BUT SOMETHING THAT BEARS WATCHING
OVER THE COMING DAYS.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 628 AM CDT TUE JUL 16 2019
SCATTERED MORNING THUNDERSTORMS IN THE VICINITY OF KHON/KSUX WILL
GRADUALLY MOVE EASTWARD WITH DRYING EXPECTED BY 16.14Z. COULD
BRIEFLY SEE MVFR CONDITIONS DUE TO REDUCED VISIBILITY/CEILINGS
WITH ANY STRONGER STORM. FOR THE REST OF TODAY, CONVECTION IS
EXPECTED TO REMAIN EAST OF TAF AIRFIELDS, ALTHOUGH SCATTERED
AFTERNOON STORMS ACROSS NORTHWEST IA COULD APPROACH KSUX ONCE
AGAIN. NOT ENOUGH CONFIDENCE TO INCLUDE IN 12Z TAFS, BUT SOMETHING
TO MONITOR THROUGH THE DAY. BETTER CHANCES FOR MORE WIDESPREAD
SHOWERS AND STORMS COMES LATE THIS EVENING AND OVERNIGHT.
INTRODUCED VCTS AT BOTH KHON/KFSD, BUT KEPT KSUX DRY AS OVERNIGHT
STORMS MIGHT NOT REACH AIRFIELD UNTIL NEAR 17.12Z.
AWAY FROM THUNDERSTORMS, VFR CONDITIONS WILL BE RULE. NORTHWEST
BREEZES AT KSUX THIS MORNING NEAR THUNDERSTORMS WILL EVENTUALLY
WEAKEN AND TURN TO THE SOUTHEAST LATER TODAY. FOR KHON/KFSD, LIGHT
AND VARIABLE WINDS WILL EVENTUALLY BECOME MORE ESTABLISHED FROM
THE EAST-NORTHEAST.
FSD WATCHES/WARNINGS/ADVISORIES
SD...EXCESSIVE HEAT WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY
EVENING FOR SDZ050-063>071.
MN...NONE.
IA...EXCESSIVE HEAT WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY
EVENING FOR IAZ001>003-012>014-020>022-031-032.
NE...EXCESSIVE HEAT WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY
EVENING FOR NEZ013-014.
SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...ROGERS
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