Severe Thunderstorm Warning 6, NWS Rapid City, SD

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
310 PM MDT FRI APR 6 2012

.DISCUSSION...WATER VAPOR IMAGERY SHOWS UPPER RIDGING ALONG THE
MISSISSIPPI VALLEY AND AN UPPER TROUGH CROSS THE NORTHERN CONUS.
DEEP SOUTHWESTERLY FLOW ALOFT IS QUICKLY DEVELOPING ACROSS THE
REGION WITH A STRONG WAVE NOW CROSSING THE AREA. SURFACE ANALYSIS
SHOWS LOW PRESSURE STRADDLING THE CWA WITH STRONG SOUTHERLY WINDS
ACROSS THE CENTRAL SOUTH DAKOTA PLAINS. ON THE BACKSIDE OF THE
LOW...GUSTY WEST/SOUTHWESTERLY WINDS ARE ACROSS EAST CENTRAL
WYOMING...AND COOLER TEMPS AND NORTHWESTERLY WINDS ARE NOTED
ACROSS NORTH CENTRAL WYOMING. RADAR SHOWS A LINE OF SHOWERS AND
STORMS ACROSS THE BLACK HILLS STRETCHING TOWARD NORTHWEST SOUTH
DAKOTA.

TONIGHT...PRECIP WILL CONTINUE TO PUSH EASTWARD AHEAD OF
THE DRY LINE/COLD FRONT CONVERGING ACROSS NORTHEAST WYOMING. LATEST
RUC SHOWS SURFACE BASED CAPE OF AROUND 1000 J/KG EXTENDING JUST
AHEAD OF THE FRONTAL BOUNDARIES...WITH DEEP SHEAR THROUGH THE LOW
TO MID LEVELS. WITH MARGINAL INSTABILITY...A FEW STORMS HAVE
ALREADY PRODUCED MODERATE SIZE HAIL. THERE IS SOME POTENTIAL FOR
ANOTHER STORM OR TWO TO PRODUCE MARGINALLY SEVERE HAIL...BUT
WIDESPREAD SEVERE WEATHER IS NOT EXPECTED. THE BEST DYNAMICS WILL
BE ACROSS NORTHWEST SOUTH DAKOTA WHERE RADAR SHOWS SOME STORMS
BEGINNING TO DEVELOP.

ADVISORY CRITERIA WINDS HAVE CONTINUE ACROSS MUCH OF THE SOUTH
DAKOTA PLAINS TODAY...BUT HAVE FAILED TO REACH ADVISORY CRITERIA
IN THE PLAINS CLOSER TO THE BLACK HILLS. MODELS ARE SUGGESTING
GUSTY WEST/SOUTHWEST WINDS WILL PUSH INTO WEST CENTRAL/SOUTHWEST
SOUTH DAKOTA THIS EVENING BEHIND THE DRY LINE. SO WILL KEEP THE
ADVISORY GOING TILL 900 PM MDT EVEN FOR THE FOOTHILLS. A COLD
FRONT WILL THEN PUSH THROUGH THE AREA LATER THIS EVENING...ENDING
THE STRONG WINDS ACROSS WEST CENTRAL/SOUTHWEST SOUTH DAKOTA
PLAINS. IT LOOKS LIKE WINDS OVER NORTHWEST SOUTH DAKOTA WILL
REMAIN AT ADVISORY CRITERIA OVERNIGHT GIVEN STRONG COLD AIR
ADVECTION...SO HAVE EXTENDING THE ADVISORY TONIGHT AND THROUGH
SATURDAY.

THE UPPER LOW WILL SWING NORTHEASTWARD INTO CANADA SATURDAY AS IT
BECOME NEGATIVELY TILTED. LATEST MODEL RUNS SHOW LINGERING PRECIP
WILL STAY NORTH OF THE CWA SATURDAY...SO HAVE REMOVED POPS. EXCEPT
FOR THE GUSTY WEST/NORTHWEST WINDS...SHOULD BE A QUIET DAY WITH
MOST AREAS SEEING SUNSHINE. HIGH PRESSURE WILL DEVELOP ACROSS THE
AREA SUNDAY BRINGING MORE SUNSHINE AND WINDS NORTHWEST WINDS AT 10
TO 20 MPH...THOUGH WINDS ACROSS NORTHWEST SOUTH DAKOTA COULD BE
STRONGER. MAX TEMPS IN THE MID 50S TO MID 60S ARE EXPECTED.

.EXTENDED...

MONDAY THROUGH FRIDAY

THE EXTENDED FORECAST REMAINS VERY COMPLICATED GIVEN A FRACTURING
WAVE OVER THE ROCKIES/UNKNOWN POSITIONING OF THE JAMES BAY
VORTEX/AND THE DEGREE OF WESTERN ATLANTIC RIDGING. FORECAST MODELS
TAKE A SPLIT PER DETAILS MID NEXT WEEK ON...WITH CLEAR DIVISION IN
ECMWF AND GFS SOLUTIONS BY THE END OF THE WEEK. A DEEP HUDSON BAY
VORTEX WITH BLOCKED DOWNSTREAM FLOW WOULD CERTAINLY OFFER MUCH
COOLER THERMAL FIELDS INTO THE AREA...AND THE GEM/ECMWF SUPPORT A
SOLUTION IN THIS DIRECTION GIVEN A WESTERN BIASED EASTERN CONUS
UPPER TROUGH. GIVEN TYPICAL POOR HANDLING OF HUDSON/JAMES BAY VORTEX
POSITIONING...WITH FORECAST MODELS TENDING TO BE BIASED TOO FAR EAST
/ESP THE GFS/ WILL SIDE HEAVIER TOWARD AN ECMWF/GEM SOLUTION. THIS
CONCERN COMBINED WITH SIGNALS FOR CONTINUED EASTERLY COMPONENT TO
THE FLOW SUPPORTS THE COOL SIDE OF GUIDANCE THROUGH THE MAJORITY OF
THE PERIOD ATTM...UNTIL TRENDS ARE ESTABLISHED. ALSO RETAINED POPS
PER THE THUR SYSTEM. TYPICALLY POORLY HANDLED FRACTURING MID LEVEL
IMPULSE CERTAINLY IS FROM BEING ASCERTAINED ATTM...WITH FORECAST
CONSISTENCY PREFERRED. CERTAINLY LOOKS TO BE A RAIN EVENT ALTHOUGH
SNOW MAY BE POSSIBLE WITH THE EXIT OF THIS SYSTEM. HENCE...ADDED A
SNOW MENTION...ESP IN LIGHT OF ECMWF/GEM THERMAL FIELDS.
OTHERWISE...DRY WEATHER EXPECTED OUTSIDE WED NIGHT-THUR ATTM.

&&

.AVIATION.../18Z TAFS/
DEEPENING LOW PRESSURE WILL FORCE A COLD FRONT THROUGH THE REGION IN
THE PERIOD. MAINLY VFR CONDITIONS THIS AFTERNOON WITH POCKETS OF
MVFR CIGS AWAY FROM THE TERMINALS. WINDS WILL VEER NW BY EARLY
EVENING WITH A FROPA...AS A GENERAL TREND...REMAINING GUSTY. WINDS
WILL BE VERY TRICKY OVER NE WY...INCLUDING GCC GIVEN A STALLED FRONT
IN PLACE. HAVE RETAINED VRBL MENTION THERE ATTM...GIVEN UNCERTAINTY
OF BOUNDARY PLACEMENT. GUIDANCE INDICATED A STRONG SOUTHERLY WIND
AHEAD OF THE COLD FRONT THERE. HOWEVER...LATEST RUC INDICATES THAT
THE SFC FRONT WILL REMAIN OVER OR JUST SOUTH OF THE TERMINAL. WILL
MONITOR. OTHERWISE...SHRA ARE EXPECTED TO DEVELOP ALONG AND AHEAD OF
THE COLD FRONT...POSSIBLY AFFECTING RAP. DETERIORATING CONDITIONS
EXPECTED AT GCC THIS EVENING GIVEN A PERIOD SNOW SHOWERS THERE. HAVE
TRENDED TO IFR CIGS. CONDITIONS WILL IMPROVE SAT AS HIGH PRESSURE
BUILDS INTO THE AREA.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 9 PM MDT /10 PM CDT/ THIS EVENING FOR
     BENNETT-CUSTER CO PLAINS-FALL RIVER-HAAKON-HERMOSA FOOT
     HILLS-JACKSON-MELLETTE-PENNINGTON CO PLAINS-RAPID CITY-
     SHANNON-SOUTHERN FOOT HILLS-TODD-TRIPP.

     FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
     EVENING FOR BADLANDS AREA-SOUTHWESTERN SOUTH DAKOTA.

     WIND ADVISORY UNTIL 9 PM MDT SATURDAY FOR BUTTE-HARDING-NORTHERN
     MEADE CO PLAINS-PERKINS-SOUTHERN MEADE CO PLAINS-ZIEBACH.

WY...FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY
     EVENING FOR LOWER ELEVATIONS OF CROOK AND WESTON COUNTIES-
     SOUTHERN CAMPBELL.

&&

SHORT TERM...13
LONG TERM...JC
AVIATION...JC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
133 PM MDT FRI APR 6 2012

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-071300-
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-
133 PM MDT (233 PM CDT) FRI APR 6 2012

...WIND ADVISORY THROUGH THIS EVENING FOR THE WESTERN AND CENTRAL
SOUTH DAKOTA PLAINS...
...FIRE WEATHER WATCH SATURDAY AFTERNOON THROUGH SATURDAY EVENING
FOR PORTIONS OF THE NORTHEAST WYOMING PLAINS AND FAR SOUTHWEST SOUTH
DAKOTA...

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS WILL CONTINUE TO CROSS PARTS OF NORTHEAST
WYOMING AND WESTERN SOUTH DAKOTA THIS AFTERNOON INTO THE EARLY
EVENING. ALTHOUGH WIDESPREAD SEVERE WEATHER IS NOT EXPECTED...A FEW
THUNDERSTORMS MAY BECOME SEVERE WITH LARGE HAIL AND DAMAGING WINDS AS
THE MAIN THREATS.

GUSTY SOUTHERLY TO WESTERLY WINDS OF 25 TO 40 MPH WILL CONTINUE
OVER MUCH OF THE AREA THIS AFTERNOON. THE WINDS WILL DIMINISH LATER
THIS EVENING. DRY CONDITIONS COMBINED WITH THE WINDS OVER FAR
SOUTHWEST SOUTH DAKOTA ARE RESULTING IN AN EXTREME GRASSLAND FIRE
DANGER.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

GUSTY NORTHWEST WINDS WILL DEVELOP OVER THE AREA ON SATURDAY. THE
WINDS WILL COMBINE WITH DRY CONDITIONS TO POSSIBLY BRING CRITICAL
FIRE WEATHER CONDITIONS TO PORTIONS OF NORTHEAST WYOMING AND
SOUTHWEST SOUTH DAKOTA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
322 PM MDT FRI APR 06 2012

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

0320 PM     HAIL             9 NNW BEAR BUTTE STATE  44.60N 103.47W
04/06/2012  E0.88 INCH       MEADE              SD   TRAINED SPOTTER

&&

JC

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RAPID CITY SD
324 PM MDT FRI APR 6 2012

SDZ012-072-073-062215-
BUTTE SD-SOUTHERN MEADE CO PLAINS SD-STURGIS/PIEDMONT FOOT HILLS SD-
324 PM MDT FRI APR 6 2012

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN MEADE AND CENTRAL BUTTE
COUNTIES UNTIL 415 PM MDT...

AT 320 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR NEWELL...OR 18 MILES NORTH OF DOWNTOWN
STURGIS...MOVING NORTHEAST AT 20 MPH.

HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  NEWELL...
  CASTLE ROCK...

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

&&

LAT...LON 4503 10344 4472 10303 4450 10350 4474 10359
TIME...MOT...LOC 2125Z 209DEG 18KT 4469 10342

BUNKERS

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RAPID CITY SD
332 PM MDT FRI APR 6 2012

SDZ027-030-041-042-062215-
CUSTER CO PLAINS SD-FALL RIVER SD-SHANNON SD-SOUTHERN FOOT HILLS SD-
332 PM MDT FRI APR 6 2012

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN FALL RIVER...EXTREME
SOUTHEASTERN CUSTER AND WESTERN SHANNON COUNTIES UNTIL 415 PM MDT...

AT 328 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 8 MILES SOUTHWEST OF OELRICHS...OR 24 MILES SOUTH
OF DOWNTOWN HOT SPRINGS...MOVING NORTHEAST AT 40 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  PINE RIDGE...
  ANGOSTURA RESERVOIR...
  OELRICHS...
  SMITHWICK...
  ORAL...
  SLIM BUTTE...
  OGLALA...

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

&&

LAT...LON 4336 10350 4357 10279 4300 10251 4299 10252
      4299 10337
TIME...MOT...LOC 2132Z 239DEG 34KT 4312 10331

BUNKERS

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