Flash Flood Warning 2, NWS Riverton, WY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1248 PM MDT SUN MAY 25 2003

...THIS AFTERNOON THROUGH WEDNESDAY...
A COUPLE OF FOCUSING MECHANISMS FOR CONVECTION THIS AFTERNOON.
FIRST IS WEAK SHORTWAVE DRIFTING NNE ACROSS SW WYOMING WITH MOISTURE
CONVERGING AHEAD/DRYING BEHIND.  SECOND IS SURFACE TROUGH ON EAST
SIDE OF DIVIDE.  BOTH THESE FEATURES TO SLOWLY DRIFT EAST THIS
EVENING WITH TROUGH NEAR A POY-HLD LINE BY 06Z. SE LOW LEVEL FLOW
WITH DEWPOINTS IN THE MID 40S TO LOWER 50S...THETA-E/CAPE TO BE
CONCENTRATED ALONG AND EAST OF TROUGH AXIS WITH DRIER MORE STABLE
WESTERLY FLOW/DEWPOINTS LOWERING INTO THE 30S TO THE WEST.  STEPPING
AWAY FROM COMPUTER SCREENS WITH A 1:SEVERAL MILLION SCALE
REPRESENTATION...CELESTIAL DOME VIEW SHOWS SOME METHOD TO THIS
MADNESS WITH WELL-DEFINED TCU/CB TO THE NORTH AND EAST...CONVECTION
BEING ENTRAINED AND LESS ORGANIZED TO THE SOUTH AND WEST.   BY THIS
EVENING BELIEVE MOST ORGANIZED ACTIVITY WILL BE FROM NEAR A
NATRONA/FREMONT COUNTY LINE UP INTO THE BIG HORN BASIN WITH BEST
COVERAGE ACROSS NORTHERN NATRONA AND JOHNSON COUNTIES.  OF COURSE...
OUTFLOW BOUNDARIES WILL LIKELY SKEW THIS NICE NEAT PICTURE A BIT.
WITH LAST EVENING AS A GUIDE...SOME OF THIS TS LIKELY TO LINGER WELL
INTO THE EVENING HOURS.   ON MEMORIAL DAY...SURFACE TROUGH AXIS TO
REMAIN IN SOMEWHAT SAME POSITION WITH PIECE OF UPPER LEVEL ENERGY
FROM NW COAST TROUGH PROGGED OVER BOUNDARY AROUND 21Z.  SECONDARY
SURFACE LOW NEAR GCC PUTS EAST SIDE OF BIG HORNS IN NORTHERLY FLOW
IN AFTERNOON WITH LESS FAVORABLE VERTICAL WIND PROFILE WITH THETA-E
GRADIENT NORTH OF SHR AND EAST OF GCC.  THUS...DO NOT SEE MUCH
POTENTIAL FOR SEVERE THRESHOLDS BEING REACHED.  MAIN UPPER TROUGH TO
MOVE ACROSS ALBERTA/SASKATCHEWAN MONDAY NIGHT DRIVING FRONT DOWN INTO
CENTRAL WYOMING BY MID-DAY.  ETA/MESO-ETA SHOWING SOME CAPE AND
THETA-E RIDGING ALONG FRONTAL BOUNDARY BUT WARM ADVECTION PROGGED
ALOFT AS UPPER RIDGE BEGINS TO BUILD BACK IN TUESDAY WITH -8C H5
ISOTHERM PUSHING INTO SW AND CAPPING THINGS.  FLOW BACKS WEDNESDAY
WITH DRY SW FLOW AND WARM AIR ALOFT WITH H7 TEMPS NEAR 15C ACROSS
CENTRAL AND SW PUTTING LOWER BASINS NEAR THE 90F MARK.

...THURSDAY THROUGH SUNDAY...COLD FRONT INTO NORTH
THURSDAY AFTERNOON AND EVENING WITH A THREAT OF THUNDERSTORMS NORTH
AND EAST. COOLER FRIDAY WITH A WARM UP ON SATURDAY WITH INCREASING
WEST WINDS WEST...SOUTH AND CENTRAL. C.BAKER

RIW...NONE.

WYZ001>020-022>030-261100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RIVERTON WY
751 AM MDT SUN MAY 25 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING.

.DAY ONE...TODAY AND TONIGHT

AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS
THE AREA PRODUCING LOCALLY HEAVY RAIN...SMALL HAIL AND STRONG WIND
GUSTS ALONG WITH LIGHTNING.  SLOW-MOVING STORMS ALONG MOUNTAIN
RANGES COMBINED WITH MELT-OFF OF HIGHER ELEVATION SNOWPACK MAY CAUSE
RAPID RISES IN DOWNSTREAM RIVERS AND STREAMS AND LOCALIZED
FLOODING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

MONDAY AND TUESDAY AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED
TO DEVELOP ACROSS THE AREA PRODUCING LOCALLY HEAVY RAIN...SMALL HAIL
AND STRONG WIND GUSTS ALONG WITH LIGHTING.  A FEW THUNDERSTORMS MAY
APPROACH SEVERE LIMITS.

SNOWMELT IN THE HIGHER ELEVATIONS OF WESTERN AND NORTHERN WYOMING
WILL CAUSE SOME RUNOFF. THUS WATER LEVELS IN MOUNTAIN STREAMS WILL
RISE LATE IN THE DAY AND DURING THE EVENING. WATER LEVELS WILL
DECREASE LATE AT NIGHT AND DURING THE MORNING HOURS WHEN RUNOFF IS
USUALLY THE LEAST. PEOPLE WITH OUTDOOR INTERESTS IN THE MOUNTAINS
THIS HOLIDAY WEEKEND SHOULD BE AWARE OF THE ABOVE INFORMATION.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

WCJIN-WYNW-WYSW-WYNE