Severe Thunderstorm Warning 140, NWS Rapid City, SD

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
232 PM MDT MON JUL 16 2012

.DISCUSSION...LATEST WATER VAPOR IMAGERY IS SHOWING TWO MOISTURE
PLUMES WITH EMBEDDED SHORTWAVES. THE FIRST EXTENDS FROM THE PACIFIC
INTO NRN AND WESTERN PORTIONS OF THE AREA WITH THE SECOND SURGING
NORTHWARD FROM THE GULF REACHING INTO SOUTHERN SOUTH DAKOTA. 20Z
SURFACE ANALYSIS AS AN AREA OF LOW PRESSURE ON TOP OF THE CWA WITH A
FRONT SPLITTING THE CWA IN HALF FROM NORTH TO SOUTH. VISIBLE
SATELLITE HAS LOTS OF CU DEVELOPING OVER THE NORTHERN BLACK HILLS
AND AREAS NORTHWARD...WITH RADAR IMAGERY AND LIGHTNING DATA SHOWING
THUNDERSTORMS ACROSS CARTER COUNTY MONTANA.

FOR TONIGHT...EMBEDDED SHORTWAVES IN THE MOISTURE PLUMES COMBINED
WITH MOISTURE CONVERGENCE ALONG THE FRONT...MODERATELY STEEP LAPSE
RATES AND MLCAPE AROUND 1000 J/KG WILL PRODUCE SCATTERED SHOWERS AND
STORMS ACROSS THE AREA. KEPT POPS SIMILAR TO PREVIOUS
FORECAST...HOWEVER DID GO WITH COVERAGE INSTEAD OF UNCERTAINTY. NAM
IS FORECASTING AND BOUNDARIES ON THE RADAR SUGGEST THE POSSIBILITY
OF SOME STORMS ALONG THE CONVERGENCE ZONE OF THE EASTERN FOOTHILLS
THAT WILL EXTEND INTO NRN SOUTH DAKOTA THAT COULD PRODUCE SOME
DAMAGING WINDS. HAVE KEPT ANY MENTION OF SEVERE STORMS OUT OF THE
FORECAST FOR NOW...BUT WILL POSSIBLY ADD THEM IN BEFORE ISSUING AS I
CONTINUE TO MONITOR THE TRENDS THIS AFTERNOON.

THE ACTIVE PATTERN CONTINUES WITH THE MAIN FORECAST CHALLENGES
BEING STORMS AND TEMPERATURES. SURFACE HIGH OVER SOUTHERN
CANADA WILL SLOWLY PUSH THE FRONT SOUTHWARD AS A LEE TROF DEEPENS
OVER EASTERN MONTANA. THIS WILL BRING EASTERLY FLOW AND AN INCREASE
IN MOISTURE TO THE AREA. INSTABILITY COMBINED WITH SURFACE HEATING
WILL BRING A CHANCE OF STORMS TUESDAY AND WEDNESDAY. KEPT CHANCE
POPS THROUGH THIS TIME AND WENT WITH HIGHER TEMPERATURES SLIGHTLY
OVER GUIDANCE SINCE MODELS HAVE BEEN RUNNING A LITTLE LOW.

EXTENDED... UPPER LEVEL RIDGE WILL REBUILD OVER THE NORTHERN AND
CENTRAL PLAINS LATE THIS WEEK AND PERSIST INTO AT LEAST THE FIRST
PART OF THE WEEKEND. THIS WILL BRING MAINLY DRY WEATHER AND WELL
ABOVE AVERAGE TEMPERATURES TO THE AREA. HIGH TEMPERATURES WILL BE
WELL INTO THE 90S...WITH TRIPLE DIGITS LIKELY FOR MOST AREAS EAST OF
THE BLACK HILLS THURSDAY...FRIDAY...AND SATURDAY. THE RIDGE IS THEN
EXPECTED TO SLOWLY SHIFT EAST OF THE AREA OVER THE WEEKEND...
ALLOWING FOR A BETTER CHANCE OF THUNDERSTORMS ACROSS NORTHEASTERN WY
AND FAR WESTERN SD LATE SATURDAY THROUGH SUNDAY. A WEAK COLD FRONT
PASSAGE WOULD ALSO BRING SLIGHTLY COOLER AIR INTO MOST OF THE AREA
BY SUNDAY.

&&

.AVIATION...18Z TAF UPDATE
SCATTERED THUNDERSTORMS WILL DEVELOP INTO THIS EVENING ACROSS
NORTHEASTERN WY AND FAR WESTERN SOUTH DAKOTA...SPREADING EASTWARD
ACROSS MUCH OF THE FORECAST AREA TONIGHT. MVFR CONDITIONS ARE
POSSIBLE WITH A FEW OF THE STRONGER STORMS. OTHERWISE VFR CONDITIONS
ARE EXPECTED THROUGH TUESDAY MORNING.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...HEAT ADVISORY UNTIL 7 PM MDT /8 PM CDT/ THIS EVENING FOR BENNETT-
     HAAKON-JACKSON-MELLETTE-TODD-TRIPP-ZIEBACH.

WY...NONE.
&&

SHORT TERM...MLS
LONG TERM...13
AVIATION...13

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
316 PM MDT MON JUL 16 2012

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-171300-
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-
316 PM MDT (416 PM CDT) MON JUL 16 2012

...HEAT ADVISORY FOR CENTRAL SOUTH DAKOTA TODAY...

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

STRONG HIGH PRESSURE WILL PERSIST ACROSS THE REGION. THIS
WILL CONTINUE TO BRING TEMPERATURES WELL ABOVE AVERAGE TO THE AREA.
ACROSS CENTRAL SOUTH DAKOTA...MAXIMUM TEMPERATURES WILL BE OVER
100 DEGREES TODAY.

SCATTERED THUNDERSTORMS...SOME OF WHICH WILL BE SEVERE...ARE
POSSIBLE OVER NORTHWESTERN SOUTH DAKOTA THIS EVENING. THE MAIN
THREATS FROM THESE STORMS WILL BE DAMAGING WINDS AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A CHANCE OF THUNDERSTORMS EXISTS TUESDAY AND WEDNESDAY...AND AGAIN
THIS WEEKEND...BUT AT THIS TIME...WIDESPREAD SEVERE WEATHER IS NOT
EXPECTED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

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