Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 202008
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
208 PM MDT WED AUG 20 2014

.SHORT TERM...TONIGHT THROUGH THURSDAY

AN UPPER LEVEL LOW PRESSURE TROUGH OVER THE NORTHERN ROCKIES EXTENDING
SOUTH INTO THE NORTHERN GREAT BASIN WILL PARTIALLY MOVE EAST ACROSS
MONTANA AND WYOMING WITH REFORMATION OCCURRING TO THE WEST THROUGH
THURSDAY. SUFFICIENT MOISTURE...SHEAR AND INSTABILITY WILL ACCOMPANY
THE TROUGH AS IT MOVES EAST FOR SCATTERED SHOWERS WITH ISOLATED
THUNDERSTORMS WITH STRONG WIND GUSTS. TEMPERATURES WILL CONTINUE A
GRADUAL COOLING TREND.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY

SHOWERS AND STORMS CONTINUE INTO THURSDAY EVENING AS THE TROUGH
CONTINUES TO TREK EAST...SENDING OUT SHORT WAVES AS IT APPROACHES.
BY FRIDAY MORNING...THE MAIN TROUGH WILL CLOSE OFF OVER WASHINGTON
AND TRACK TO IDAHO BY FRIDAY NIGHT. THERE WILL BE PLENTY OF UPPER
LEVEL DYNAMICS WITH THE APPROACHING JET AND BROAD LIFT AHEAD OF
THE TROUGH TO ENHANCE SHOWER AND THUNDERSTORM COVERAGE...SO POPS
WERE BUMPED UP A BIT FOR FRIDAY...KEEPING WITH THE TREND FROM THE
PREVIOUS SHIFT.

ON SATURDAY...THE MAIN TROUGH MOVES INTO THE REGION...SENDING A
SIGNIFICANT COLD FRONT THROUGH THE FORECAST AREA WITH A GOOD CHANCE
OF SHOWERS AND SOME THUNDERSTORMS ALONG WITH SOME SNOW TO THE
HIGHER MOUNTAINS. THE MODELS HAVE YET TO AGREE ON EXACTLY HOW COLD
IT WILL BE BUT THE LATEST THINKING IS THAT SNOW LEVELS COULD DROP
TO 9KFT LATE SATURDAY NIGHT.

THE FLOW FLATTENS ON SUNDAY...TURNING DRIER AND MORE STABLE
HOWEVER ANOTHER TROUGH WILL BE APPROACHING THE REGION...WHICH
COULD BEGIN TO AFFECT THE FAR NORTHWEST BY THE EVENING...OTHERWISE
FLOW WILL SLOWLY TURN BACK TO THE SOUTHWEST. THERE COULD BE
ANOTHER ROUND OF SHOWERS...THUNDERSTORMS AND PERHAPS EVEN SOME
MORE HIGH ELEVATION SNOW MONDAY NIGHT INTO TUESDAY WITH MODELS
TRYING TO BUILD A RIDGE IN THEREAFTER...WHERE THE RIDGE IS
CENTERED REMAINS UNCERTAIN BUT THERE IS AGREEMENT IN A WARM UP BY
MID WEEK.

&&

.AVIATION.../00Z ISSUANCE/

AN UPPER LEVEL LOW PRESSURE TROUGH OVER THE NORTHERN ROCKIES
EXTENDING SOUTH INTO THE NORTHERN GREAT BASIN WILL PARTIALLY MOVE EAST
ACROSS MONTANA AND WYOMING WITH REFORMATION OCCURRING TO THE WEST
THROUGH 00Z FRIDAY. SUFFICIENT MOISTURE...SHEAR AND INSTABILITY WILL
ACCOMPANY THE TROUGH AS IT MOVES EAST FOR SCATTERED SHOWERS WITH
ISOLATED THUNDERSTORMS WITH STRONG WIND GUSTS. LOCAL IFR
CONDITIONS MAY PERSIST IN THE FAR WESTERN VALLEYS WHERE STRATUS
REMAINS TRAPPED IN JACKSON HOLE...YELLOWSTONE NATIONAL PARK AND
THE STAR VALLEY. THE SHOWERS AND THUNDERSTORMS WILL BE MOST
NUMEROUS THROUGH 06Z THURSDAY WITH LOCAL MOUNTAIN OBSCURATIONS
EXPECTED.

SOME SHOWERS AND POSSIBLE THUNDERSTORMS WILL LINGER THROUGH THE
NIGHT AND THURSDAY MORNING...ESPECIALLY OVER THE WESTERN
MOUNTAINS. THEN SHOWERS AND ISOLATED THUNDERSTORMS WILL AGAIN BECOME
MORE NUMEROUS BETWEEN 18Z THURSDAY AND 00Z FRIDAY WITH LOCAL MOUNTAIN
OBSCURATIONS.

&&

.FIRE WEATHER...

AN UPPER LEVEL LOW PRESSURE TROUGH OVER THE NORTHERN ROCKIES
EXTENDING SOUTH INTO THE NORTHERN GREAT BASIN WILL PARTIALLY MOVE EAST
ACROSS MONTANA AND WYOMING WITH REFORMATION OCCURRING TO THE WEST
THROUGH THURSDAY. SUFFICIENT MOISTURE...SHEAR AND INSTABILITY WILL
ACCOMPANY THE TROUGH AS IT MOVES EAST FOR SCATTERED SHOWERS WITH
ISOLATED THUNDERSTORMS WITH STRONG WIND GUSTS.  TEMPERATURES WILL
CONTINUE A GRADUAL COOLING TREND WITH INCREASING RELATIVE
HUMIDITY. THERE WILL BE SUFFICIENT MOISTURE AVAILABLE TO KEEP
MIXING HEIGHTS SUPPRESSED...ESPECIALLY OVER THE WEST.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...ALLEN
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER






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