Damaging Wind in Wyoming, August 18, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
226 PM MDT SAT AUG 18 2001

SAT IMAGERY SHOWING SHORTWAVE TREKKING ACROSS WYOMING THIS
AFTERNOON.  CU FORMING OVER WESTERN WYOMING.  THE ONLY THUNDERSTORMS
ARE JUST SOUTH OF BORDER NEAR FLAMING GORGE AND TO THE NORTH OF
YELLOWSTONE AND ABSAROKAS.  TEMPS MAINLY IN THE 80S...EXCEPT FOR LOW
90S IN BIG HORN BASIN AND JOHNSON COUNTY.

MODEL LI/S BEST OVER WESTERN AND SOUTHWESTERN WYOMING THIS EVENING.
WILL LEAVE ISOLATED POPS THERE.  A WEAK COLD FRONT MOVES THROUGH
WYOMING FROM THE NORTHWEST LATE TONIGHT...BUT GETS CAUGHT FROM
AN ARCH FROM EVANSTON TO TOGWOTEE THEN TO BUFFALO AND ON EAST.
THIS WILL BRING IN SLIGHTLY COOLER AIR FOR SUNDAY TO AREAS BEHIND
THE FRONT.  AN AREA OF CHANNELED VORTICITY IN THE WESTERLY FLOW
ENTERS WESTERN WYOMING SUNDAY MORNING AND SPREADS EAST ACROSS THE
NORTH THROUGH THE DAY.  LOOKS LIKE THE BEST CHANCE FOR CONVECTION TO
BE NORTHWEST MOUNTAINS...SO WILL LEAVE THE ISOLD THUNDERSTORMS THERE.
CLOUDS WILL MOVE ACROSS THE STATE WITH THE VORT AREA.  GRADIENT
DOESN/T LOOK SO IMPRESSIVE FOR TOMORROW SO WILL BACK DOWN BREEZY
SOME AREAS.  THE FRONT PROGRESSES THROUGH CASPER SUNDAY NIGHT AFTER
BEING HUNG UP ALL DAY ACROSS SOUTHERN JOHNSON COUNTY.  SOUTHWEST
FLOW PICKS UP MONDAY WITH AREA OF HIGH PRESSURE BUILDING OVER THE
FOUR CORNERS LATE SUNDAY.  THE MOVES OFF THE EAST MONDAY RESULTING
IN A RETURN OF MONSOON...WHICH TRIES TO REACH EXTREME SOUTHERN
WYOMING LATE MONDAY AFTERNOON.  WILL ADD ISOLD THUNDERSTORMS TO RKS
ZONE LATE MONDAY AFTERNOON AND EVENING PERIODS.  OTHER SOUTHERN
ZONES WILL JUST ADD INCREASING AFTERNOON CLOUDS.

IN THE EXTENDED...MONSOON COUNTIES THROUGH WEDNESDAY UNTIL A PAC TROF
MOVES ON SHORE...BRINING ADDED CHANCE FOR SHOWERS AND
THUNDERSTORMS. EXTENDED TEMPS DONT LOOK AS COOL AS THEY DID
YESTERDAY...WILL ONLY MAKE MINOR ADJUSTMENTS TO TEMPS FROM PREVIOUS
PACKAGE.

RIW...RED FLAG WARNING WESTERN...SOUTHERN ZONES AND NORTHERN
MOUNTAINS.

TWB