Severe Thunderstorm Warning 352, NWS Rapid City, SD

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
100 PM MDT THU AUG 11 2011

.DISCUSSION...CURRENT SURFACE ANALYSIS PLACES LOW OVER SOUTHEAST
MONTANA INTO NORTHEAST WYOMING WHILE HIGH REMAINS NEAR THE MIDWEST.
SOUTHERLY/EASTERLY FLOW AHEAD OF THE LOW CONTINUES TO BRING
INCREASED MOISTURE INTO THE CWFA. UPPER LEVEL ANALYSIS PLACES
WESTERLY FLOW OVER OUR AREA WHILE INITIAL SHORT WAVE PUSHES OVER THE
NRN CWFA...BRINGING SCT THUNDERSTORMS TO THE AREA. COMPACT LOW
OVER SRN ALBERTA/NWRN MT CONTINUES TO PUSH EASTERLY WITH VARIOUS
WAVES AHEAD OF IT.

FOR THIS AFTERNOON INTO TONIGHT...TIMING OF STORM DEVELOPMENT WILL
BE TRICKY TODAY WITH THE VARIOUS SHORT WAVES MOVING THROUGH THE
AREA. MODELS NOW SUGGESTING AN INITIAL ROUND EARLY WITH THE CURRENT
WAVE...THEN A SECOND ROUND TOWARDS EVENING WITH THE APPROACH OF THE
MAIN LOW/WAVE. STRONG INSTABILITY IS NOTED INTO NERN WYO INTO
WRN/CNTRL SD...WITH THE STRONGEST INSTABILITY EAST OF THE BLACK
HILLS WHERE MODELS ADVERTISE CAPE VALUES OF ~2-3 KJ/KG. PLENTY OF
SHEAR IS AVAILABLE FOR SUPERCELLS WITH 40-55 KTS 0-6 KM BULK. HRRR
SUGGESTING DISCRETE STORMS WITH THE FIRST ROUND WHICH WOULD BE
CONDUCIVE TO LARGE HAIL...WITH STORMS BECOMING MORE LINEAR LATER
WHICH WOULD LEAN MORE TOWARDS A WIND THREAT. ALSO...WITH LOW LEVEL
SHEAR INCREASING AHEAD OF SFC LOW WILL HAVE TO WATCH FOR POSSIBLE
TORNADIC THREAT THIS AFT/EARLY EVE...PARTICULARLY TOWARDS CNTRL SD.

ON FRIDAY...STRONG UPPER WAVE PASSES TO THE NORTH OF THE
CWFA...THOUGH WITH CYCLONIC FLOW ALOFT EXPECT SOME SHOWERS AND
THUNDERSTORMS THROUGH THE DAY. EXPECT STORMS TO REMAIN TAME AS
STRONGEST INSTABILITY WILL BE TO THE EAST. DRY WEATHER IS EXPECTED
BY EVENING AS RIDGE BUILDS IN.

FOR SATURDAY...RIDGE CONTINUES TO BUILD IN BRINGING A DRY DAY TO THE
AREA.

EXTENDED...AN UPPER LEVEL RIDGE OVER THE CENTRAL UNITED STATES WILL
SLOWLY SHIFT EAST INTO EARLY NEXT WEEK CREATING ACTIVE SOUTHWESTERLY
FLOW ALOFT OVER THE FORECAST AREA. THERE WILL BE A SLIGHT CHANCE OF
MAINLY AFTERNOON AND EVENING THUNDERSTORMS NEARLY EVERY DAY WITH
TEMPERATURES NEAR SLIGHTLY ABOVE NORMAL.

&&

.AVIATION...SCATTERED THUNDERSTORMS ARE EXPECTED THROUGH MUCH OF THE
NIGHT. SOME THUNDERSTORMS MAY BE SEVERE IN THE EVENING WITH LARGE
HAIL AND STRONG WINDS. OTHERWISE...VFR CONDITIONS ARE EXPECTED.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
115 PM MDT THU AUG 11 2011

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-121300-
BENNETT-BUTTE-CENTRAL BLACK HILLS-CUSTER CO PLAINS-FALL RIVER-HAAKON-
HARDING-HERMOSA FOOT HILLS-JACKSON-MELLETTE-NORTHEASTERN CROOK-
NORTHERN BLACK HILLS-NORTHERN CAMPBELL-NORTHERN FOOT HILLS-
NORTHERN MEADE CO PLAINS-PENNINGTON CO PLAINS-PERKINS-RAPID CITY-
SHANNON-SOUTHERN BLACK HILLS-SOUTHERN CAMPBELL-SOUTHERN FOOT HILLS-
SOUTHERN MEADE CO PLAINS-STURGIS/PIEDMONT FOOT HILLS-TODD-TRIPP-
WESTERN CROOK-WESTON-WYOMING BLACK HILLS-ZIEBACH-
115 PM MDT (215 PM CDT) THU AUG 11 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN SOUTH DAKOTA AND
NORTHEASTERN WYOMING.

.DAY ONE...TODAY AND TONIGHT

AN APPROACHING UPPER LEVEL DISTURBANCE WILL BRING SCATTERED
THUNDERSTORMS THIS AFTERNOON INTO THIS EVENING. THERE IS A SLIGHT
RISK THAT SOME OF THESE STORMS MAY BECOME SEVERE...WITH LARGE HAIL
AND DAMAGING WINDS AS THE MAIN THREATS. THERE IS ALSO A LOW TORNADIC
THREAT FOR THIS AFTERNOON INTO EARLY THIS EVENING...PARTICULARLY
TOWARDS CENTRAL INTO PARTS OF WESTERN SOUTH DAKOTA.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS FRIDAY ACROSS CENTRAL
SOUTH DAKOTA. THERE ARE ALSO DAILY CHANCES FOR THUNDERSTORMS SUNDAY
THROUGH WEDNESDAY. WIDESPREAD SEVERE WEATHER IS NOT EXPECTED AT THIS
TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RAPID CITY SD
1245 PM MDT THU AUG 11 2011

SDZ026-028-111915-
CENTRAL BLACK HILLS SD-RAPID CITY SD-
1245 PM MDT THU AUG 11 2011

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL PENNINGTON COUNTY UNTIL
115 PM MDT...

AT 1242 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
A STRONG THUNDERSTORM NEAR JOHNSON SIDING...OR 10 MILES NORTHEAST OF
HILL CITY...MOVING SOUTHEAST AT 20 MPH.

HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  HISEGA...
  SHERIDAN LAKE...
  ROCKERVILLE...

IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A
STURDY BUILDING.

RICHARDS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
113 PM MDT THU AUG 11 2011

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

1250 PM     HAIL             4 S PACTOLA RESERVOIR   44.01N 103.50W
08/11/2011  E1.00 INCH       PENNINGTON         SD   PUBLIC

&&

WFO UNR

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
116 PM MDT THU AUG 11 2011

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

0100 PM     HAIL             7 SW DOWNTOWN RAPID CIT 44.00N 103.33W
08/11/2011  M0.88 INCH       PENNINGTON         SD   TRAINED SPOTTER

&&

KCLARK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
212 PM MDT THU AUG 11 2011

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

0155 PM     HAIL             6 NW MILESVILLE         44.52N 101.77W
08/11/2011  E2.75 INCH       HAAKON             SD   PUBLIC

&&

KCLARK