Hail and Damaging Winds in South Dakota, August 14, 2006

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
230 PM MDT MON AUG 14 2006

.DISCUSSION...CURRENT SURFACE ANALYSIS PLACES BROAD AREA OF HIGH
PRESSURE THROUGH THE CENTRAL AND NORTHERN PLAINS...WITH WEAK TROF
FROM CENTRAL MONTANA INTO CENTRAL WYOMING. GENERALLY WEST-NORTHWEST
FLOW OVER THE AREA...THOUGH A VARIETY OF SHORT WAVES CONTINUE TO
MOVE THROUGH. CLOSEST WAVE IS PUSHING INTO THE SOUTHWEST PTN OF
CWFA...WITH SOME TCU CURRENTLY DEVELOPING OVER THE BLK HILLS INTO
SOUTHWEST SOUTH DAKOTA. MODELS ARE INDICATING A FAIR AMOUNT OF CAPE
OVER FAR SOUTHWEST SD INTO THE HILLS...AS ETA IS INDICATING CAPE
VALUES OF 1000-1800 J/KG...AND LAST RUN OF THE RUC IS PUSHING CAPE
VALUES OVER 2000 J/KG. MODELS ALSO INDICATE STEEP LAPSE AND ADEQUATE
SHEAR PROFILES FOR SUPERCELLS. THUS...A SEVERE THUNDERSTORM WATCH
HAS BEEN ISSUED FOR THAT AREA UNTIL EARLY THIS EVENING. LARGE HAIL
WILL BE THE MAIN THREAT...THOUGH DAMAGING WIND GUSTS WILL ALSO BE A
POSSIBILITY. FOR LATER ON TONIGHT...LOW LEVEL JET WILL SET UP WITH A
FAIR AMOUNT OF THETA-E ADVECTION...THEREFORE CONTINUED POPS INTO THE
OVERNIGHT HOURS. FOR TOMORROW...MAIN CONCERN WILL BE WINDS. MODELS
ARE INDICATING A TIGHT PRESSURE GRADIENT SETTING UP...PARTICULARLY
OVER THE EASTERN CWFA. WINDS WILL INCREASE TO 20 TO 30 MPH OVER
EASTERN CWFA ONCE FULL MIXING OCCURS. ANOTHER WAVE WILL MOVE THROUGH
THE AREA IN THE AFTERNOON INTO THE EVENING...WITH THE LOW LEVEL JET
SETTING UP AGAIN LATE IN THE EVENING...BRINGING ANOTHER CHANCE FOR
THUNDERSTORMS. FOR WEDNESDAY AND THURSDAY...UPPER FLOW WILL SHIFT
SOUTHWEST AS AN UPPER LEVEL TROF MOVES INTO THE PACIFIC NORTHWEST.
THIS WILL OPEN THE DOOR FOR MULTIPLE DISTURBANCES TO MOVE THROUGH.
TEMPERATURES WILL BE IN THE 90S ON BOTH DAYS. THE BEST CHANCE FOR
PRECIP WILL COME ON THURSDAY AS THE MAIN TROUGH AXIS AND COLD FRONT
MOVE INTO THE REGION.

EXTENDED...HIGH PRESSURE WILL BUILD INTO THE REGION ON FRI AND SAT
IN WAKE OF CDFNT...BRINGING DRY WX WITH TEMPS NEAR AVERAGE. TEMPS
WILL BE ON THE REBOUND FOR SUN AND MON AS UPR RIDGE BUILDS INTO THE
NRN ROCKIES...AND WILL CONTINUE WITH DRY FCST AS UPR RIDGE AXIS TO
OUR WEST SHOULD SUPPRESS MOST CONVECTION.

&&

.AVIATION...SCATTERED THUNDERSTORMS WILL OCCUR THIS AFTERNOON ALONG
ROUTES 258...259...AND...285. THUNDERSTORM ACTIVITY IS EXPECTED TO
TAPER OFF LATE THIS EVENING. IFR/MVFR CONDITIONS WILL BE COMMON IN
ANY THUNDERSTORMS THAT DEVELOP...OTHERWISE VFR CONDITIONS EXPECTED.

&&

.FIRE WEATHER...AN UPPER LEVEL RIDGE OF HIGH PRESSURE IS IN CONTROL
OVER THE NORTHERN PLAINS TUESDAY BRINGING A RETURN TO TEMPERATURES
IN THE MID 90S AND LOW RELATIVE HUMIDITIES AROUND 15 TO 25 PERCENT.
IN ADDITION...A TIGHT PRESSURE GRADIENT ACROSS THE AREA WILL
INCREASE SOUTHERLY WINDS TO NEAR 30 MPH ACROSS SOUTH CENTRAL SOUTH
DAKOTA. SINCE THESE VALUES ARE EXPECTED TO EXCEED OR COME CLOSE TO
EXCEEDING CRITERIA...WILL GO WITH A FIRE WEATHER WATCH FOR THE SOUTH
DAKOTA PLAINS FOR TOMORROW. EXPECT SIMILAR CONDITIONS ON WEDNESDAY
SO WILL CONTINUE TO MONITOR THE SITUATION IN CASE THE WATCH NEEDS TO
BE EXTENDED.

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
1150 AM MDT MON AUG 14 2006

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-151300-
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-
1150 AM MDT (1250 PM CDT) MON AUG 14 2006

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

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON INTO
THIS EVENING FOR FAR SOUTHWEST SOUTH DAKOTA INCLUDING THE BLACK
HILLS ALONG WITH PARTS OF NORTHEAST WYOMING.

ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED THIS AFTERNOON INTO
THIS EVENING. SOME OF THESE THUNDERSTORMS WILL HAVE THE POTENTIAL
TO BECOME SEVERE...PARTICULARLY OVER THE BLACK HILLS...FAR
SOUTHWEST SOUTH DAKOTA...AND PARTS OF FAR NORTHEAST WYOMING ADJACENT
TO THE BLACK HILLS. LARGE HAIL WILL BE THE MAIN THREAT...THOUGH
DAMAGING WIND GUSTS WILL ALSO BE POSSIBLE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

PASSING UPPER LEVEL DISTURBANCES WILL BRING AFTERNOON AND EVENING
THUNDERSTORMS TO THE AREA TUESDAY THROUGH THURSDAY. SEVERE
THUNDERSTORM DEVELOPMENT IS POSSIBLE WEDNESDAY AND THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY.