Damaging Wind in South Dakota, May 7, 2009

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
635 PM MDT WED MAY 6 2009

.UPDATE...THE FORECAST IS ON TRACK AND NO MAJOR UPDATES WERE MADE.
THE MAIN ADJUSTMENT WAS TO CHANGE FROM PROBABILITY TO CATEGORICAL
WORDING AS SHOWERS ARE ALREADY SPREADING ACROSS NERN WY AND WRN SD.
THE 00Z KUNR SOUNDING HAD 88 J/KG OF MUCAPE...SO THERE STILL IS A
CHANCE OF ISOLATED THUNDER. WATER VAPOR AND RADAR IMAGES INDICATE
PRECIP SHOULD BE ON THE UPTICK OVER THE NEXT SEVERAL HOURS.

PREVIOUS DISCUSSION...WATER VAPOR IMAGERY SHOWS AN UPPER LOW JUST
NORTH OF NORTH DAKOTA DRIFTING EASTWARD WITH NEAR ZONAL FLOW TO THE
SOUTH ACROSS THE REGION. ALSO EVIDENT ARE SEVERAL SHORTWAVES NOW
ENTERING WESTERN WYOMING AND APPROACHING THE AREA. THIS FORCING WILL
BRING A CHANCE OF SHOWERS TO THE CWA TONIGHT. FORECAST SOUNDINGS
SHOW MUCAPE VALUES ON THE WEAK SIDE...SO COULD ALSO SEE ISOLATED
THUNDERSTORMS DEVELOP TONIGHT. SEVERE WEATHER IS NOT EXPECTED GIVEN
THE WEAK INSTABILITY.

ZONAL FLOW WILL CONTINUE THURSDAY WITH HIGHS NEAR TO SLIGHTLY ABOVE
AVERAGE. SHORTWAVES WILL CONTINUE TO CROSS THE REGION KEEPING A
CHANCE OF SHOWERS/STORMS ACROSS MUCH OF THE AREA. CLOUDS AND THE
CHANCE FOR PRECIP WILL INCREASE LATE THURSDAY INTO THURSDAY NIGHT AS
A STRONGER SHORTWAVE DROPS FROM CANADA AND CROSSES EASTERN MONTANA.
A COLD FRONT WILL ALSO CROSS THE AREA WITH COOLER AIR SPILLING INTO
THE REGION FRIDAY...LIMITING HIGHS TO THE 50S ACROSS MOST LOCATIONS.
CYCLONIC FLOW AND COOL AIR ALOFT WILL KEEP STEEP LAPSE RATES ACROSS
THE AREA WITH SHOWERS AND THUNDERSTORMS CONTINUING. WEAK UPPER LEVEL
RIDGING IS EXPECTED TO BUILD IN FRIDAY NIGHT WITH PRECIP DECREASING
INTO THE EARLY MORNING HOURS.

EXTENDED...AN UNSETTLED WEATHER PATTERN WILL PERSIST THROUGH THE
EXTENDED PERIOD AS ZONAL FLOW REMAINS OVER THE NORTHERN PLAINS. A
SERIES OF SHORTWAVES WILL CROSS THE AREA DURING THIS TIME...
PRODUCING RAIN SHOWERS AND THUNDERSTORMS. EXACT TIMING FOR THESE
SHORTWAVES REMAINS UNCERTAIN THIS FAR OUT...SO WILL KEEP
BROADBRUSHED POPS EACH PERIOD. TEMPERATURES WILL REMAIN NEAR TO
SLIGHTLY ABOVE SEASONAL AVERAGES.

&&

.AVIATION...MAINLY VFR CONDITIONS WILL CONTINUE THROUGH THURSDAY
MORNING. ISOLATED TO SCATTERED SHOWERS CAN BE EXPECTED AGAIN
TONIGHT...WITH A FEW THUNDERSTORMS POSSIBLE IN THE EVENING.

&&

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

&&

BUNKERS/CALDERON/ST

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
335 AM MDT WED MAY 6 2009

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-071400-
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-
335 AM MDT (435 AM CDT) WED MAY 6 2009

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

.DAY ONE...TODAY AND TONIGHT

AN UPPER LEVEL DISTURBANCE CROSSING THE AREA WILL CREATE A CHANCE OF
THUNDERSTORMS TONIGHT. SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS
TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THERE IS A CHANCE OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS OVER
VARIOUS PARTS OF THE AREA FROM THURSDAY THROUGH TUESDAY. WIDESPREAD
SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY.