Severe Thunderstorm Warning 149, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
408 PM CDT TUE JUL 6 2010

.DISCUSSION...
CONVECTION BREAKING OUT RIGHT ON TRACK WITH THE SHORT RANGE HRRR
MODEL IN SCNTRL SD...AND CONCERN IN THE SHORT TERM LARGELY ON THE
SEVERE WEATHER AND HEAVY RAIN THREAT. MID AFTERNOON SFC ANALYSIS
INDICATES BNDRY SHARPENING UP THRU SCNTRL SD...WITH MOISTURE TONGUE
WRAPPED FROM BACKED SERN SD/NERN NEBRASKA FLOW. THIS HAS RESULTED IN
ARND 2000 J/KG MLCAPE...ONLY WKLY CAPPED. SHEAR PARAMETERS ARE EVEN
A BIT BETTER AT LOW LVLS THAN EARLIER PROGGED...WITH A GREATLY
TURNING AND STRONGER WIND FLOW THRU LOWEST 2KM.  LOWER BRULE AREA
REALLY A FOCUS FOR BEST OVERLAP OF EXISTING LOW LVL VORTICITY WITHIN
FRONTOGENETIC ZONE...AND 0-3KM CAPE. TOR WATCH WAS ISSUED SHORTLY
AFT 2PM.  SHEAR DOES NOT SEEM TO SUPPORT MOTION SUGGESTED BY HRRR
WHICH RACES SUPERCELLULAR STRUCTURES INTO THE KFSD AREA BY 01Z...BUT
RATHER WOULD SUGGEST A MODEST EWRD PROGRESSION TO AREA OF CONVECTION.
THIS SFC BASED CONVECTION WOULD THEN PERHAPS FIND A WEAKENING OF
COVERAGE LATER THIS EVENING AS WAVE STARTS TO SHEAR NEWRD THRU ND.
ADDITIONAL IMPULSE REINFORCES FRONTAL LINEAR FORCING LATER TONIGHT...
AND INCREASED POPS LATER ON IN NIGHT TO REFLECT STRONGER FORCING AS
BODILY TROUGH PUSHES EWRD LATE NIGHT.

ALSO A HEAVY RAIN THREAT AS DEEPER WIND MOTION HAS STRONGLY PARALLEL
COMPONENT TO BOUNDARY. FOR THE TIME...DID NOT ISSUE FFA AS STORMS
SHUD BE A BIT MORE DISCRETE TO START...BUT EVENING ACTION MAY SET UP
ADDITIONAL PROBLEMS FOR LATER NIGHT ACTIVITY...AND CAN ADDRESS AFTER
THE SHORT TERM SVR THREAT. /CHAPMAN

WEDNESDAY LOOKS LIKE A DAY WITH THE POTENTIAL FOR OCCASIONAL SHOWERS
AND THUNDERSTORMS THROUGHOUT THE DAY WITH LITTLE IN THE WAY OF
CAPPING AND A WEAK AND MOIST SFC BOUNDARY HANGING AROUND. THE THREAT
FOR SEVERE FAIRLY MINIMAL...BUT WOULD NOT BE SURPRISED AT A FEW
ISOLATED HAILER OR HIGH WIND REPORTS. INITIALLY THE BETTER CHANCE
SHOULD BE CONFINED TO THE NORTHWEST HALF OF THE CWA...SO DECREASED
HIGHS A SMIDGE...WHILE INCREASING A BIT OVER THE SOUTHEAST HALF AS
THE THREAT FOR THUNDERSTORMS SHOULD BE LATER. DID INCREASE TO 60-70
POPS FOR THE ENTIRE AREA THROUGH THE DAY.

BY WEDNESDAY NIGHT THE MAIN THREAT WILL BE LIFTING OUT SO HAVE POPS
MAINLY ALONG AND EAST OF I29 IN THE EVENING. AFTER THIS SHOULD BE
CLEARING SKIES AND DECREASING HUMIDITY. LOWS LIKELY IN THE 50S.

THURSDAY AND FRIDAY LOOK LIKE VERY NICE DAYS WITH NO MAJOR THREAT
FOR THUNDERSTORMS...WINDS MAINLY UNDER 15 MPH AND MOSTLY SUNNY
SKIES.LOWS IN THE 50S AND HIGHS IN THE 80S.

IN THE LATTER PERIODS(SAT/TUE)...OVERALL LOOKS LIKE THE POTENTIAL TO
CONTINUE WITH A RELATIVELY BUSY PATTERN. GENERALLY FAST WEST TO
NORTHWEST FLOW EXPECTED ALOFT WITH SOME POORLY AGREED UPON TROFING
SOMETIME OVER THE WEEKEND. SO...WILL NEED LOW END POPS FOR MUCH OF
THE PERIOD WITH THIS PATTERN...AND EXPECT TEMPERATURES TO BE NEAR
NORMAL THROUGHOUT. SATURDAY NIGHT INTO SUNDAY DOES LOOK LIKE A
PERIOD WHERE TEMPERATURES COULD BE A LITTLE ABOVE NORMAL ASSUMING
THUNDERSTORMS ARE NOT TOO WIDESPREAD. /08

&&

.AVIATION...
CONVECTIVE POTENTIAL LARGEST CHALLENGE TO TAFS.  MAIN AREA UNDER THE
GUN FOR SFC THREAT WOULD BE KHON AND AREAS FROM JAMES VALLEY AND
WWRD THRU THE EARLY EVNG. THE CONVECTIVE ACTIVITY WILL LIKELY
PRODUCE HEAVY RAIN REDUCING VISIBILITIES BRIEFLY BLO 1SM...BUT
TAFWISE WOULD SEEM THAT 2SM WOULD BE SUFFICIENT. THESE STORMS WILL
AFFECT THE KHON TERMINAL AFTER 22Z...AND TOWARD/AFT 12Z WEDNESDAY AT
THE KFSD AND KSUX TERMINALS. /CHAPMAN

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1145 AM CDT TUE JUL 06 2010

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-071200-
AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA-
CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE-
DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON-
IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN-
LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN-
OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN-
SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON-
1145 AM CDT TUE JUL 06 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA...
SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
INITIAL DEVELOPMENT OF THUNDERSTORMS IS EXPECTED VERY LATE THIS
AFTERNOON INTO EARLY EVENING FROM THE MID JAMES VALLEY TOWARD THE
LOWER BRULE AREA.  EARLY DISCRETE STORMS WILL BE CAPABLE OF HAIL
TO GOLF BALL SIZE...WIND GUSTS TO 65 MPH...AND EVEN A BRIEF
TORNADO.  THESE STORMS ARE EXPECTED TO BECOME MORE NUMEROUS
THROUGH THE EVENING HOURS...WITH THE THREAT TRANSITIONING TO MORE
DAMAGING WIND AND HAIL TO QUARTER SIZE MOVING EAST TOWARD DE
SMET...MITCHELL...AND LAKE ANDES.  THE SLOW EASTWARD MOVEMENT OF
STORMS OVERNIGHT WILL ALSO CONTRIBUTE TO A HEAVY RAINFALL
THREAT...WITH ANOTHER INCH TO TWO OF RAINFALL POSSIBLE FOR
LOCATIONS WEST OF A DE SMET TO LAKE ANDES LINE.

FLOODING...
THE JAMES RIVER WILL REMAIN IN FLOOD FOR THE FORESEEABLE FUTURE.
ELSEWHERE...RIVERS CONTINUE TO FALL. THE LITTLE SIOUX RIVER NEAR
LINN GROVE WILL ALSO BE IN FLOOD UNTIL MID WEEK. ADDITIONAL HEAVY
RAINFALL OVER THE NEXT DAY OR TWO COULD STALL OR REVERSE FALLING
TRENDS IN AREA RIVER LEVELS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

SHOWERS AND A FEW THUNDERSTORMS WILL MOVE EAST AND SOUTHEAST OVER
THE AREA THROUGH WEDNESDAY. LOCALLY HEAVY RAIN WILL BE
POSSIBLE...ALONG WITH ISOLATED SEVERE STORMS MAINLY SOUTHEAST OF
A LINE FROM MARSHALL TO YANKTON...BUT A WIDESPREAD SEVERE WEATHER
THREAT IS NOT EXPECTED.

THE PATTERN WILL STILL BE FAVORABLE FOR A FEW SEVERE OR HEAVY
THUNDERSTORMS AT TIMES FROM LATE SATURDAY INTO NEXT WEEK...MAINLY
IN THE NIGHTTIME HOURS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE POSSIBLE AFTER 5 PM CDT WEST OF THE
JAMES RIVER.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
737 PM CDT TUE JUL 06 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0727 PM     TORNADO          3 ESE HARRISON          43.43N 98.47W
07/06/2010                   DOUGLAS            SD   TRAINED SPOTTER

            TORNADO ON THE GROUND MOVING EAST.

&&

MDB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
743 PM CDT TUE JUL 06 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0655 PM     HAIL             4 W HARRISON            43.44N 98.61W
07/06/2010  M1.75 INCH       DOUGLAS            SD   TRAINED SPOTTER

            GOLF BALL SIZE HAIL STRIPPED CORN.

&&

MDB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
807 PM CDT TUE JUL 06 2010

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0735 PM     HAIL             6 ENE PUKWANA           43.81N 99.07W
07/06/2010  E1.00 INCH       BRULE              SD   PUBLIC

            MARBLE TO QUARTER SIZE HAIL COVERED THE GROUND.

&&

WILLIAMS