Severe Thunderstorm Warning 45, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
311 PM MDT WED JUN 25 2008

.SHORT TERM...TONIGHT THROUGH SATURDAY
UPDATED FOR SEVERE THUNDERSTORM WATCH NUMBER 605 WHICH INCLUDES
JOHNSON...WASHAKIE AND BIG HORN COUNTIES THROUGH 9 PM. ISOLATED
SEVERE THUNDERSTORMS COULD ALSO AFFECT OTHER AREAS TO THE SOUTH
AND WEST BUT THE HIGHEST PROBABILITY SHOULD REMAIN IN AND NEAR THE
WATCH AREA.

TWO DISTINCT SHORTWAVES MOVING THROUGH THE AREA TODAY WITH THE
SOUTHERN ONE BRINGING A FEW STRONG...GUSTY THUNDERSTORMS TO THE
RED DESERT WITH ONE AT OR NEAR SEVERE LEVELS. NRN SHORTWAVE MOVING
INTO OUR NRN ZONES WITH SOME CONVECTION FROM AHEAD OF IT. CLOUDS
HAVE HELD THE TEMPS DOWN IN OUR CNTRL ZONES EARLIER BUT NOW TEMPS
ARE SOARING. DEW POINTS ARE MIXING DOWN THOUGH WITH IT IN THE WIND
RIVER BASIN. HIGHER DEW POINTS ARE STILL HOLDING IN THE CODY
FOOTHILLS...BIG HORN BASIN...JOHNSON AND NATRONA COUNTIES. THREAT
FOR AT LEAST ISOLATED SEVERE WILL EXIST INTO THE EARLY EVENING
HOURS EAST OF THE DIVIDE WITH CLOUD/CLOUD FREE AREAS ALSO PLAYING
INTO THE MIX ALONG WITH OUTFLOW BOUNDARIES AND POSSIBLE UPSLOPE SE
FLOW IN SPOTS. ANOTHER LATE EVENING SHORTWAVE AHEAD OF APPROACHING
SHORTWAVE MAY KEEP ISOLATED CONVECTION GOING ACROSS THE WEST AND
NORTH OVERNIGHT.

ON THURSDAY...SHORTWAVE TROUGH WILL APPROACH THE WEST BY LATE
AFTERNOON WITH POTENTIAL RIGHT ENTRANCE REGION JET STREAK AND MID
LEVEL COOLING. POTENTIAL FOR AN ACTIVE DAY IS THERE IN THE NW
FIRST AND THEN SPREAD SOUTHEAST ALONG THE COLD FRONT. HAVE
INDICATED ISOLATED SEVERE THREAT ALONG THE FRONT AS IT MOVES THROUGH.
WINDS SHOULD SHIFT TO THE NORTH BEHIND THE FRONT EAST OF THE
DIVIDE. EVENTUALLY THIS FRONT WILL EVEN MAKE INTO THE RED DESERT.
FRIDAY WILL BE COOLER AND STABLE BEHIND THIS FRONT WITH GENERAL
NORTHEAST SURFACE FLOW. TEMPERATURES BEGIN TO REBOUND SATURDAY BUT
ATMOSPHERE WILL LIKELY NOT RECOVER ENOUGH QUITE YET TO ADD
ISOLATED STORMS BACK INTO THE FORECAST.

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
MEDIUM RANGE MODELS IN DECENT AGREEMENT THAT THE LONG TERM WILL BE
DOMINATED BY AN UPPER LEVEL RIDGE. THIS RIDGE IS EXPECTED TO BE
THE STRONGEST DURING THE WEEKEND...WITH THE WARMEST DAY EXPECTED
TO BE ON SUNDAY WITH TEMPERATURES 5 TO 10 DEGREES ABOVE AVERAGE.
LITTLE PRECIPITATION IS EXPECTED OVER THE WEEKEND...WITH THE BEST
CHANCE OVER THE NORTHERN HIGHER TERRAIN ON SUNDAY...BUT THIS
SHOULD REMAIN ISOLATED. BY NEXT WORK WEEK...THIS RIDGE WILL WEAKEN
SOME...WITH SEVERAL DISTURBANCES IN THIS RIDGE INTERACTING WITH
SUFFICIENT MOISTURE FOR ISOLATED TO LOCALLY SCATTERED AFTERNOON/EVENING
CONVECTION OVER MUCH OF THE CWA...WITH THE SOUTHWEST BEING THE
DRIEST AREA OF THE FORECAST AREA. TEMPERATURES WILL REMAIN AROUND 5
DEGREES ABOVE AVERAGE MONDAY THROUGH WEDNESDAY.

&&

.AVIATION...
A COUPLE OF UPPER LEVEL DISTURBANCES IN THE SOUTHWEST FLOW WILL
BISECT A FIELD OF LOW LEVEL MOISTURE THAT FILTERED IN OVERNIGHT
BEHIND LAST NIGHTS COOL FRONT AS WELL AS INTERACT WITH INCREASING
INSTABILITY. THIS PROCESS WILL INITIATE SIGNIFICANT THUNDERSTORM
ACTIVITY THIS AFTERNOON...MAINLY ACROSS AREAS EAST OF THE
CONTINENTAL DIVIDE. THIS THUNDERSTORM ACTIVITY WILL LAST WELL INTO
THE EVENING ACROSS JOHNSON AND NATRONA COUNTIES. SOME OF THESE
STORMS COULD BECOME SEVERE ACROSS NORTHERN AND EASTERN WYOMING ALONG
WITH DAMAGING WINDS AND LARGE HAIL. THE THUNDERSTORMS EXPECTED TODAY
WILL CAUSE SCATTERED MVFR CONDITIONS ALONG WITH ISOLATED IFR
CONDITIONS AND MOUNTAIN OBSCURATIONS IN THE VICINITY OF THE STRONGER
THUNDERSTORMS. THURSDAY IS EXPECTED TO BE ANOTHER ACTIVE DAY AS FAR
AS THUNDERSTORMS ARE CONCERNED...ESPECIALLY ACROSS THE NORTHERN TWO
THIRDS OF WYOMING...AS ANOTHER UPPER LEVEL DISTURBANCE IN THE
SOUTHWEST FLOW AFFECTS THE AREA. ANOTHER COLD FRONT MOVING SOUTH
ACROSS WYOMING BEHIND THIS FEATURE WILL HELP FOCUS THE THUNDERSTORMS
ACTIVITY AS THE FRONT PROPAGATES SOUTH THURSDAY AFTERNOON AND
EVENING. THUNDERSTORMS COULD AGAIN BECOME SEVERE IN NORTHERN AND
EASTERN ZONES. AGAIN...THE THUNDERSTORMS EXPECTED THURSDAY WILL
CAUSE SCATTERED MVFR CONDITIONS ALONG WITH ISOLATED IFR CONDITIONS
AND MOUNTAIN OBSCURATIONS IN THE VICINITY OF THE STRONGER
THUNDERSTORMS.

&&

.FIRE WEATHER...
THUNDERSTORMS WILL BE SCATTERED EAST OF THE DIVIDE THROUGH THE EVENING
HOURS...SOME OF THESE MAY BE QUITE STRONG TO EVEN SEVERE WITH
LARGE HAIL AND DAMAGING WIND GUSTS. A FEW STRONG THUNDERSTORMS ARE
ALSO EXPECTED ACROSS THE RED DESERT WITH THE THREAT OF DAMAGING
WIND GUSTS. ISOLATED SHOWERS AND THUNDERSTORMS MAY EVEN CONTINUE
OVERNIGHT...ESPECIALLY ACROSS THE WEST AND NORTH. ON THURSDAY...AN
APPROACHING WEATHER DISTURBANCE WILL BRING AN INCREASING CHANCE OF
STRONG THUNDERSTORMS TO NORTHWEST WYOMING AS A STRONG COLD FRONT
MOVES SOUTHEAST ACROSS THE AREA. THUNDERSTORMS WILL MOVE ALONG AND
AHEAD OF THIS FRONT AND SPREAD INTO THE NORTHERN ZONES IN THE
EARLY AFTERNOON...GRADUALLY SPREADING SOUTH AND EAST BY LATE
AFTERNOON.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

SHORT TERM...SKRBAC
LONG TERM...WM
AVIATION...LIPSON
FIRE WEATHER...SKRBAC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
307 PM MDT WED JUN 25 2008

WYZ001>020-022>030-261100-
ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST-
BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS-
EAST SWEETWATER COUNTY-FLAMING GORGE-
GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS-
NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN-
NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS-
ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES-
SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN-
SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY-
TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN-
UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN-
WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST-
YELLOWSTONE NATIONAL PARK-
307 PM MDT WED JUN 25 2008

...FLOOD WARNING IN EFFECT FOR LOCATIONS ALONG THE NORTH FORK
SHOSHONE RIVER IN PARK COUNTY...
...SEVERE THUNDERSTORM WATCH FOR JOHNSON...WASHAKIE AND BIG HORN
COUNTIES THROUGH 9 PM THIS EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

SEVERE THUNDERSTORMS ARE POSSIBLE EAST OF THE CONTINENTAL DIVIDE...
ESPECIALLY ACROSS JOHNSON...BIG HORN AND WASHAKIE COUNTIES.
THE SEVERE STORMS WILL BE CAPABLE OF PRODUCING HAIL AND DAMAGING WIND
GUSTS OVER 60 MPH. ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED
OVER WESTERN AND CENTRAL WYOMING. THESE THUNDERSTORMS SHOULD BE
WEAKER BUT CAPABLE OF PRODUCING BRIEF HEAVY RAIN AND STRONG WIND
GUSTS TO 50 MPH ALONG WITH OCCASIONAL CLOUD TO GROUND LIGHTNING.
PEOPLE PLANNING OUTDOOR ACTIVITIES THIS AFTERNOON AND EVENING SHOULD
BE PREPARED TO SEEK NEARBY SHELTER AS THESE STORMS DEVELOP.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE POSSIBILITY OF SCATTERED AFTERNOON AND EVENING THUNDERSTORMS WILL
CONTINUE ACROSS MAINLY NORTH AND EAST-CENTRAL WYOMING THURSDAY
AFTERNOON AND EVENING ALONG A STRONG COLD FRONT. ISOLATED SEVERE
THUNDERSTORMS WITH LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE...
MAINLY OVER THE NORTH AND EAST-CENTRAL THURSDAY AFTERNOON AND
EVENING. COOLER CONDITIONS EAST OF THE DIVIDE ARE EXPECTED FOR
FRIDAY.

SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO REPORT ANY HAIL SIZES...ALONG WITH ANY
WINDS OF 40 MPH OR GREATER THIS AFTERNOON AND EVENING.

TEAM RIVERTON

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