Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 312040
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
240 PM MDT FRI OCT 31 2014

.SHORT TERM...TONIGHT THROUGH SATURDAY

A FAST MOVING PACIFIC LOW PRESSURE TROUGH OVER EASTERN NEVADA AND
WESTERN IDAHO WILL SWEEP EAST ACROSS WESTERN AND CENTRAL WYOMING
SATURDAY.  AHEAD OF THE TROUGH SOUTHWEST WINDS ALOFT WILL INCREASE
BRINGING BREEZY TO WINDY CONDITIONS ALONG AND EAST OF THE
CONTINENTAL DIVIDE AND THROUGH THE WIND CORRIDOR FROM ROCK SPRINGS
TO CASPER.  OVER THE WESTERN MOUNTAINS AND VALLEYS CLOUDS WILL
INCREASE AND LOWER THROUGH THE NIGHT WITH SOME MOUNTAIN SHOWERS
DEVELOPING LATE TONIGHT AND EARLY SATURDAY MORNING. CLOUDS AND
SHOWERS WILL INCREASE THROUGH SATURDAY MORNING WITH MAINLY SNOW
ABOVE 8500 FEET. LOCAL SNOWFALL OF 2 TO 4 INCHES CAN BE EXPECTED
IN THE FAR WEST MOUNTAINS.  IN THE AFTERNOON THE AIR MASS IS
EXPECTED TO BE UNSTABLE ENOUGH FOR ISOLATED THUNDERSTORMS EMBEDDED
IN THE SHOWERS...ESPECIALLY OVER THE MOUNTAINS.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY

THE HEAVIEST PRECIPITATION IN THE UPCOMING PRECIPITATION EVENT IN
THE WEST STILL LOOKS TO FALL BETWEEN 00Z AND 06Z ON SUNDAY. DURING
THIS TIME THE DEEPEST MOISTURE ALONG WITH SOME LIFT FROM THE
APPROACHING FRONT AND SOME UPPER LEVEL DYNAMICS FROM THE LEFT FRONT
QUAD OF A JET STREAK WILL BRING THE STEADIEST PRECIPITATION. WITH
COLD AIR ADVECTING IN...SNOW LEVELS SHOULD FALL TO THE VALLEY FLOORS
AS WE HEAD TOWARD MIDNIGHT. AS FOR AMOUNTS...THERE COULD BE SOME
ADVISORY LEVEL AMOUNTS. HOWEVER...AT THIS TIME THESE LOOK TO BE
CONFINED TO THE HIGHER ELEVATIONS. STILL SOME TIME TO DETERMINE IF
HIGHLIGHTS ARE WARRANTED. THE HEAVIEST RAIN AND SNOW SHOULD END
AFTER MIDNIGHT SATURDAY NIGHT...ALTHOUGH WITH UPSLOPE FLOW SOME
SHOWERS WILL CONTINUE LATE AT NIGHT AND INTO SUNDAY AS WELL.
MEANWHILE...EAST OF THE MOUNTAINS ALL THE MODELS HAVE TRENDED DRIER
SATURDAY NIGHT INTO SUNDAY WITH THE BEST LIFT MOVING INTO MONTANA.
AS A RESULT WE TRIMMED POPS A BIT WITH SLIGHT CHANCES REMAINING
ACROSS NORTHERN AREAS. WINDS WILL CONTINUE TO BE GUSTY AHEAD OF THE
COLD FRONT BEFORE LESSENING LATER AT NIGHT AND INTO SUNDAY. THE BIG
CHANGE EAST OF THE DIVIDE WILL BE TEMPERATURES WILL SUNDAY RUNNING
10 TO 20 DEGREES COOLER THAN ON SATURDAY. WITH FLOW GOING NORTHWEST
SUNDAY NIGHT...WE WILL HAVE TO WATCH OUT FOR THOSE PAIN IN THE NECK
SNOW BANDS THAT LIKE TO THROW A MONKEY WRENCH INTO THE FORECAST. IT
IS WAY TO EARLY TO PINPOINT THEM...BUT SOMETHING TO WATCH.

BY MONDAY...THE FRONT AND ENERGY WILL BE AWAY TO THE EAST. THE
EUROPEAN MODEL CONTINUES TO SHOW A BIT OF ENERGY MOVING NORTHWARD
AND SCRAPING THE SOUTHEASTERN PORTIONS OF THE COUNTY WARNING AREA
WITH A BIT OF QPF. THE AMERICAN MODELS HAVE NOTHING SO WE WILL KEEP
THE FORECAST MAINLY DRY AT THIS POINT. ELSEWHERE...SOME WEAK RIDGING
SHOULD HELP TO SHUT OFF ANY SHOWERS ACROSS THE WEST. IT WILL BE A
CHILLY DAY HOWEVER WITH TEMPERATURES AVERAGING BELOW NORMAL FOR MOST
LOCATIONS. ON TUESDAY...THE GFS SHOWS ANOTHER SHORTWAVE MOVING INTO
NORTHWESTERN WYOMING WITH ANOTHER ROUND OF SHOWERS...ALTHOUGH NOT A
LOT OF MOISTURE TO WORK WITH. MEANWHILE...THE EUROPEAN IS MUCH DRIER
AND BUILDS RIDGING MORE STRONGLY OVER THE AREA AND KEEPS THE
PRECIPITATION TO THE NORTH AND WEST. WE KEPT SLIGHT POPS ACROSS THE
NORTHWEST BUT IT DOES NOT LOOK LIKE A BIG EVENT. AREAS EAST OF THE
DIVIDE SHOULD STAY DRY DUE TO A DOWNSLOPING BREEZE. A DRYING AND
WARMING TREND WILL THEN BE THE RULE FROM WEDNESDAY INTO FRIDAY AS
RIDGING REBUILDS ACROSS THE WESTERN US AND BRINGS A RETURN TO ABOVE
NORMAL TEMPERATURES. THE MODELS DO HAVE A COUPLE OF SHORTWAVES
BRUSHING BY TO THE NORTH AND WEST BUT WITH TIMING ALL OVER THE
PLACE...WE KEPT THE FORECAST MAINLY DRY AT THIS POINT.

&&

.AVIATION.../00Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

THE TAF AIRPORTS WILL GENERALLY HAVE PREVAILING VFR CONDITIONS
THROUGH 00Z SATURDAY...ALTHOUGH KCOD AND SURROUNDING SITES COULD
SEE MVFR CONDITIONS DEVELOP AROUND 00Z. STRENGTHENING SOUTHWEST
FLOW ALOFT WILL INCREASE MID TO HIGH LEVEL CLOUDS BY 15Z
SATURDAY...WHICH WILL CONTINUE THROUGH 00Z. GUSTY SOUTHWEST WINDS
WILL DEVELOP FROM KRKS TO KCPR TO KBYG TONIGHT. THIS STRONG SOUTHWEST
FLOW WILL THEN BRING STRONG DOWNSLOPE WINDS...AND AREAS OF LOW
LEVEL WIND SHEAR...TO MANY AREAS EAST OF THE DIVIDE...WITH 30-40
KNOT GUSTS POSSIBLE...SATURDAY MORNING AND AFTERNOON. SOME
AIRPORTS ALONG AND EAST OF THE CONTINENTAL DIVIDE ABOVE 9000
FEET...COULD SEE MVFR CEILINGS AND VISIBILITIES...SATURDAY MORNING
AND AFTERNOON...AS SNOW SHOWERS PUSH IN.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

THE AIRPORTS WILL HAVE PREVAILING VFR CONDITIONS THROUGH 10Z
SATURDAY. SOUTHWEST FLOW ALOFT WILL INCREASE MID AND UPPER LEVEL
CLOUDS THROUGHOUT THE NIGHT...WITH MVFR CEILINGS AND VISIBILITIES
POSSIBLE AFTER 10Z...OVER THE WESTERN MOUNTAINS AND VALLEYS.
ISOLATED RAIN SHOWERS...AND SNOW SHOWERS ABOVE 8000 FEET...WILL BE
POSSIBLE ACROSS THE WESTERN MOUNTAINS AND VALLEYS BETWEEN 12Z-18Z.
CHANCES FOR RAIN SHOWERS...AND HIGHER ELEVATION SNOW...THEN INCREASE
SATURDAY AFTERNOON WEST OF THE DIVIDE...WITH A FEW ISOLATED
THUNDERSTORMS ALSO POSSIBLE. GUSTY WINDS WILL DEVELOP ACROSS KRKS
AND SOUTHERN WYOMING TONIGHT...AND CONTINUE THROUGH THE AFTERNOON
SATURDAY. SOUTHWESTERN WYOMING...INCLUDING KBPI AND KPNA...COULD
ALSO SEE GUSTY WINDS DEVELOP...MAINLY AFTER 18Z SATURDAY.


&&

.FIRE WEATHER...

A FAST MOVING PACIFIC LOW PRESSURE TROUGH OVER EASTERN NEVADA AND
WESTERN IDAHO WILL SWEEP EAST ACROSS WESTERN AND CENTRAL WYOMING
SATURDAY AND SATURDAY EVENING. AHEAD OF THE TROUGH SOUTHWEST WINDS
ALOFT WILL INCREASE BRINGING BREEZY TO WINDY CONDITIONS ALONG AND
EAST OF THE CONTINENTAL DIVIDE AND THROUGH THE WIND CORRIDOR FROM
ROCK SPRINGS TO CASPER. OVER THE WESTERN MOUNTAINS AND VALLEYS
CLOUDS WILL INCREASE AND LOWER THROUGH THE NIGHT WITH SOME MOUNTAIN
SHOWERS DEVELOPING LATE TONIGHT AND EARLY SATURDAY MORNING. CLOUDS
AND SHOWERS WILL INCREASE THROUGH SATURDAY MORNING WITH MAINLY
SNOW ABOVE 8500 FEET. IN THE AFTERNOON THE AIR MASS IS EXPECTED TO
BE UNSTABLE ENOUGH FOR ISOLATED THUNDERSTORMS EMBEDDED IN THE
SHOWERS...ESPECIALLY OVER THE MOUNTAINS.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...HATTINGS
AVIATION...ANGLIN
FIRE WEATHER...C.BAKER









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