High Wind in South Dakota, April 18, 2007

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
935 AM MDT WED APR 18 2007

.DISCUSSION...CURRENT SURFACE ANALYSIS HAS DEEPENING AREA OF LOW
PRESSURE CENTERED OVER NORTH CENTRAL WY WITH TIGHT PRESSURE GRADIENT
OVER THE NORTHERN HIGH PLAINS. WINDS BEGINNING TO INCREASE ACROSS
THE AREA AS BOUNDARY LAYER MIXES OUT. UPPER LEVEL ANALYSIS SHOWS
TROF AXIS ACROSS THE GREAT BASIN WITH SOUTH-SOUTHWEST FLOW ACROSS
THE PLAINS. STRONG UPPER JET IS ROUNDING THE TROF WITH SHORTWAVE
ENERGY MOVING OUT OF UT AND INTO SOUTHERN WY. THIS COULD BRING A FEW
SHOWERS AND THUNDERSTORMS TO NORTHEAST WY BY LATE AFTERNOON.
OTHERWISE...MAIN CHANCES FOR PCPN WILL HOLD OFF UNTIL TONIGHT.

ONLY VERY MINOR TWEAKS MADE TO TODAYS FORECAST FOR NOW...MAINLY TO
ACCOUNT FOR CURRENT CONDITIONS. WILL CONTINUE TO MONITOR WINDS...BUT
LOOKS LIKE COVERAGE OF WIND ADVISORY IS GOOD. HOWEVER...AM WORRIED A
BIT ABOUT WINDS REACHING WARNING CRITERIA ACROSS FAR NORTHWEST SD
THIS AFTERNOON...MAINLY HARDING AND POSSIBLY PERKINS CO. MAY NEED TO
UPGRADE THOSE AREAS BY THIS AFTERNOON...BUT NO ZONE UPDATE IS
PLANNED AT THE MOMENT.

&&

.AVIATION...VFR CONDITIONS EXPECTED INTO THIS EVENING. SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE OVER EASTERN WYOMING...WESTERN SOUTH
DAKOTA AND THE NEBRASKA PANHANDLE LATE THIS AFTERNOON AND EVENING.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY THROUGH 900PM MDT THIS EVENING FOR MUCH OF
     WESTERN SD.
WY...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
630 AM MDT WED APR 18 2007

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-191300-
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-
630 AM MDT (730 AM CDT) WED APR 18 2007

...WIND ADVISORY IN EFFECT FROM 900 AM MDT UNTIL 900 PM MDT FOR MUCH
OF WESTERN SOUTH DAKOTA...

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

.DAY ONE...TODAY AND TONIGHT

VERY WINDY CONDITIONS WILL DEVELOP THIS MORNING OVER NORTHEAST
WYOMING AND MUCH OF WESTERN SOUTH DAKOTA. SOUTH TO SOUTHEAST WINDS
WILL INCREASE TO 25 TO 40 MPH WITH GUSTS TO 50 MPH. THE WINDS WILL
SLOWLY TAPER OFF THIS EVENING.

AN UPPER LEVEL DISTURBANCE APPROACHING THE AREA WILL RESULT IN
THUNDERSTORMS DEVELOPING OVER NORTHEAST WYOMING THIS AFTERNOON
BEFORE SPREADING INTO WESTERN AND SOUTH CENTRAL SOUTH DAKOTA THROUGH
THE EVENING HOURS. THOUGH WIDESPREAD SEVERE WEATHER IS NOT
ANTICIPATED AT THIS TIME...A FEW OF THE STORMS OVER NORTHEAST WYOMING
AND FAR WESTERN SOUTH DAKOTA MAY HAVE THE POTENTIAL TO BECOME
SEVERE LATE THIS AFTERNOON INTO EARLY THIS EVENING. IF ANY DO BECOME
SEVERE...LARGE HAIL AND DAMAGING WIND GUSTS WILL BE THE MAIN THREATS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE CHANCE FOR THUNDERSTORMS WILL CONTINUE INTO THURSDAY...MAINLY
OVER WESTERN INTO SOUTH CENTRAL SOUTH DAKOTA. THE STORMS ON
THURSDAY ARE NOT EXPECTED TO BECOME SEVERE.

THE NEXT CHANCE FOR THUNDERSTORMS WILL COME FRIDAY EVENING INTO
SATURDAY AS ANOTHER UPPER LEVEL DISTURBANCE APPROACHES THE AREA.
SOME OF THESE STORMS WILL HAVE THE POTENTIAL TO BECOME SEVERE ON
SATURDAY...PARTICULARLY OVER SOUTH CENTRAL SOUTH DAKOTA EAST OF A
LINE FROM PHILIP TO MARTIN. THE PRIMARY THREATS FROM THESE STORMS
WILL BE LARGE HAIL AND DAMAGING WIND GUSTS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY.