096
FXUS65 KRIW 240846
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
246 AM MDT THU JUL 24 2008
SHORT TERM
TODAY THROUGH SATURDAY NIGHT
GFS AND NAM IN GOOD AGREEMENT ON THE TRACK OF THE SHORTWAVE
CURRENTLY OVER THE INTERIOR PAC NW AND SHOW THIS SYSTEM MOVING
SLIGHTLY TO THE NORTH OF EAST TODAY ACROSS NORTHERN MT/SOUTHERN
ALBERTA AND SOUTHERN SASKATCHEWAN INTO NORTHERN ND/SOUTHERN MANITOBA
BY 06Z FRIDAY. AS THE SHORTWAVE MOVES TO THE NORTH OF THE REGION
TODAY AND TONIGHT...A WEAK COLD FRONT WILL MOVE INTO NORTHEASTERN
WY ACROSS JOHNSON COUNTY TO THE EAST SLOPES OF THE BIGHORN MOUNTAINS
AND INTO NORTHERN NATRONA COUNTY. NORTHEASTERN LOW LEVEL FLOW ACROSS
THE EASTERN CWA WILL KEEP DEWPOINTS IN THE 40S TO NEAR 50. ALTHOUGH
THE NAM INDICATES MUCH HIGHER CAPE VALUES AND LOWER LIFTED INDICES
THAN THE GFS...THERE SHOULD BE ADEQUATE INSTABILITY TO SUPPORT
ISOLATED SHOWERS AND THUNDERSTORMS ACROSS JOHNSON COUNTY...NATRONA
COUNTY AND THE BIGHORN MOUNTAINS THIS AFTERNOON AND EVENING. THE
HIGHEST PRECIPITABLE WATER VALUES OF NEAR 1.0 INCH WILL BE IN
JOHNSON COUNTY AND LARGE HAIL WILL BE POSSIBLE IN STRONGER
THUNDERSTORMS. ISOLATED SHOWERS AND THUNDERSTORMS WHICH FORM OVER
THE UINTAS ARE ALSO EXPECTED TO DRIFT ACROSS PORTIONS OF SWEETWATER
COUNTY THIS AFTERNOON. THIS CONVECTION SHOULD END LATE THIS
AFTERNOON...AS DRIER LOW LEVEL AIR MOVES ACROSS WESTERN WY INTO
CENTRAL WY. WEAK COLD FRONT WILL PRODUCE NEAR NORMAL HIGH
TEMPERATURES ACROSS THE NORTHEASTERN CWA...WHILE FLAT RIDGE ALOFT
AND H7 TEMPERATURES BETWEEN 14 AND 17 C WILL RESULT IN ABOVE NORMAL
HIGH TEMPERATURES ACROSS THE REMAINDER OF THE REGION.
THE UPPER RIDGE WILL BUILD ACROSS WY FRIDAY...AND RETURN FLOW AROUND
SURFACE HIGH PRESSURE CENTERED IN THE WESTERN DAKOTAS WILL ADVECT
LOW LEVEL MOISTURE ACROSS JOHNSON AND NATRONA COUNTIES. BOTH THE GFS
AND NAM INDICATE THAT PRECIPITABLE WATER VALUES WILL REMAIN BETWEEN
0.75 AN 1.0 INCHES FRIDAY AFTERNOON AND EVENING. THE AVAILABLE
MOISTURE...A VEERING WIND PROFILE AND STRONG SURFACE HEATING FRIDAY
AFTERNOON ARE EXPECTED TO GENERATE ISOLATED CONVECTIVE ACTIVITY
ACROSS JOHNSON AND NATRONA COUNTIES THROUGH FRIDAY EVENING DESPITE
MODERATE H5 HEIGHT RISES. ACROSS THE REMAINDER OF THE CWA FRIDAY IT
WILL CONTINUE TO BE DRY WITH ABOVE NORMAL TEMPERATURES...AS THE
RIDGE BUILDS INTO THE NORTHERN ROCKIES. THE UPPER RIDGE WILL CREST
ACROSS WY SATURDAY...AND WESTERLY BOUNDARY AND H7/H5 WINDS WILL
CONTINUE TO ADVECT A DRIER AIRMASS ACROSS THE REGION. RESIDUAL LOW
LEVEL MOISTURE ACROSS JOHNSON COUNTY COULD RESULT IN WIDELY ISOLATED
SHOWERS AND THUNDERSTORMS. STRONG SUBSIDENCE ALOFT BENEATH THE LARGE
RIDGE WILL PRODUCE ANOTHER DRY DAY FOR MOST OF THE CWA HOWEVER WITH
HIGHS IN THE 90S TO NEAR 100 IN THE LOWER ELEVATIONS EAST OF THE
DIVIDE.
LONG TERM
SUNDAY THROUGH THURSDAY
UPPER RIDGE OVER THE AREA SUNDAY. HOT DAY IN STORE WITH ONLY
ISOLATED STORMS OVER THE MOUNTAINS AND IN THE EAST ZONES. A
SHORTWAVE IS FORECAST TO MOVE THROUGH MONTANA MONDAY WHICH WILL
FLATTEN THE RIDGE. AGAIN ISOLATED STORMS OVER THE NORTH AND EAST
ZONES MONDAY AFTERNOON AND EVENING. MOSTLY DRY CONDITIONS CENTRAL
AND SOUTH DUE TO DRY AIRMASS FORECAST. ON TUESDAY SOME MID LEVEL
MOISTURE MAY RETURN TO THE AREA WITH LOW LEVEL MOISTURE IN THE NORTH
AND EAST ZONES. HAVE GONE WITH ISOLATED STORMS FOR ALL AREAS IN THE
AFTERNOON AND EVENING. GFS INDICATES MORE MOISTURE IN THE FLOW
WEDNESDAY ALONG WITH ADEQUATE DEWPOINT VALUES. THUS WILL GO WITH
ISOLATED AFTERNOON AND EVE STORMS ALL LOCATIONS. LITTLE CHANGE IN
THE PATTERN NEXT THURSDAY AND WILL KEEP ISOLATED STORMS IN THE
FORECAST. TEMPS MONDAY THRU THURSDAY WILL STAY VERY WARM TO HOT WITH
MONDAY AND TUESDAY A LITTLE COOLER THAN SUNDAY...THEN WARMING UP
NEXT WED AND THURS.
AVIATION
A DRIER AIRMASS AND INCREASING WESTERLY WINDS WILL PUSH ACROSS
WESTERN WYOMING LATE THIS MORNING AND OVER THE CONTINENTAL DIVIDE
INTO WEST CENTRAL WYOMING EARLY THIS AFTERNOON. ISOLATED
THUNDERSTORMS WILL FIRE OFF A DRYLINE NEAR THE BIG HORN MOUNTAINS
AND WESTERN NATRONA COUNTY THURSDAY AFTERNOON AFFECTING KCPR-KWRL
ROUTES AND POINTS NORTH.
FIRE WEATHER
LOW LEVEL MOISTURE WILL LINGER ACROSS NORTHEAST WYOMING TODAY
THROUGH FRIDAY...AS UPPER LEVEL HIGH PRESSURE BUILDS ACROSS THE
REGION FROM THE SOUTHWEST. ISOLATED AFTERNOON AND EVENING SHOWERS
AND THUNDERSTORMS ARE EXPECTED IN JOHNSON AND NATRONA COUNTIES AND
THE BIGHORN MOUNTAINS DURING THE AFTERNOON AND EVENING TODAY AND
FRIDAY. WETTING RAINS AND STRONG OUTFLOW WINDS WILL BE POSSIBLE IN
THE STRONGER STORMS ACROSS THESE AREAS BOTH DAYS. WEST WINDS ACROSS
THE REMAINDER OF THE REGION TODAY AND FRIDAY WILL TRANSPORT DRIER
AIR INTO THE AREA FROM THE WEST. HIGH TEMPERATURES TODAY AND FRIDAY
WILL CONTINUE ABOVE NORMAL UNDER THE INFLUENCE OF LARGE HIGH
PRESSURE ALOFT.
RIW WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...SMITH
LONG TERM...AR
AVIATION...AEM
FIRE WEATHER...SMITH
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