Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 210524
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1124 PM MDT MON OCT 20 2014

.SHORT TERM...TONIGHT THROUGH TUESDAY

THE UPPER LEVEL HIGH PRESSURE RIDGE THAT HAS BROUGHT MILD...DRY
AND STABLE CONDITIONS TO WESTERN AND CENTRAL WYOMING OVER THE WEEKEND
HAS SHIFTED EAST INTO THE GREAT PLAINS AS A FAST MOVING PACIFIC
TROUGH MOVES INLAND INTO THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA.  THIS WILL BRING INCREASING SOUTHWEST FLOW
ALOFT...INSTABILITY AND MOISTURE TO THE AREA AS THE TROUGH
APPROACHES WESTERN WYOMING.  WINDS WILL INCREASE TONIGHT AND TUESDAY
BECOMING WINDY OVER AND NEAR THE MOUNTAINS AND THROUGH THE WIND
CORRIDOR. SOME GUSTS TO 45 MPH CAN BE EXPECTED FROM ROCK SPRINGS
THROUGH SOUTH PASS TO CASPER...AND IN THE CODY FOOTHILLS. SHOWERS
AND CLOUDS WILL INCREASE OVER THE WEST LATER TONIGHT AND BECOME MORE
WIDESPREAD OVER THE MOUNTAINS THROUGH TUESDAY. ISOLATED
THUNDERSTORMS CANNOT BE RULED OUT WITH MARGINAL INSTABILITY AND
INCREASING JET DYNAMICS OVER THE AREA. THE LOWER ELEVATIONS EAST OF
THE CONTINENTAL DIVIDE SHOULD REMAIN DRY BUT WILL SEE MORE CLOUD
COVER BRINGING SOME COOLING.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

THE APPROACHING TROUGH ON TUESDAY LOOKS TO SPLIT AS IT MOVES ACROSS
THE CWA ON TUESDAY EVENING. AS THE SYSTEM SPLITS...THE SEGMENTS OF
PRECIPITATION WILL MOVE TO THE NORTH AND SOUTH BRINGING DRYING
CONDITIONS ACROSS THE FORECAST AREA BY WEDNESDAY MORNING. A BUILDING
RIDGE WILL KEEP QUIET CONDITIONS OVER THE AREA FOR THE NEXT SEVERAL
DAYS.

TEMPERATURES WILL WARM UNDER THE APPROACHING TROUGH...AND SOME AREAS
OF PRECIPITATION WILL APPROACH THE FORECAST AREA FROM THE WEST. A
FEW ROGUE SHOWERS MAY BE POSSIBLE THROUGH THE REST OF THE
WEEK...THOUGH THE DRY CONDITIONS ARE EXPECTED TO REMAIN PREVALENT
THROUGH SATURDAY. AN APPROACHING TROUGH OF LOW PRESSURE WILL MOVE
OFF THE PACIFIC COAST SATURDAY AND BEGIN TO MOVE EAST TOWARDS THE
FORECAST AREA.

THE TROUGH WILL BEGIN TO INFLUENCE THE FORECAST AREA EARLY
SUNDAY...POTENTIALLY SPREADING SHOWER ACTIVITY ACROSS MUCH OF
WESTERN AND CENTRAL WYOMING THROUGH SUNDAY AFTERNOON. COOLER
TEMPERATURES WILL ALSO BE FOUND WITH THIS SYSTEM AS IT USHERS IN
COOLER H7 TEMPERATURES. THE TROUGH WILL MOVE QUICKLY THROUGH THE
FORECAST AREA...WITH A RETURN OF NORTHWEST FLOW ANTICIPATED BY
MONDAY AFTERNOON.

.AVIATION.../06Z ISSUANCE/
BOTH THE GFS AND NAM ADVERTISING THAT THE UPPER LOW OVER NORTHERN
CALIFORNIA WILL TRACK NORTHEAST AND SWING ACROSS NORTHWEST WYOMING
TODAY. JET ENERGY AND APPROACH OF THE SHORTWAVE WILL ASSIST
DEVELOPMENT OF RAIN/SNOW SHOWERS ACROSS THE NORTHWEST AFTER ABOUT
12Z-14Z TODAY. EXPECT WIDESPREAD MOUNTAIN TOP OBSCURATIONS ACROSS
THE NORTHWEST BETWEEN 12Z-23Z. COULD BE BRIEF PERIOD OF MVFR WITH
HEAVIER RAIN SHOWERS AT KJAC BETWEEN 16Z-21Z AS COLD FRONT PUSHES
THROUGH THE FAR WEST. OTHERWISE...KJAC WILL STAY VFR THROUGH THE
PERIOD WITH CLEARING SKIES AFTER 00Z/WED. CONVECTIVE SHOWERS WILL
BREAK OUT AHEAD OF THE COLD FRONT EARLY THIS AFTERNOON. BEST CHANCE
WILL BE ACROSS THE SOUTHWEST TERMINALS OF KBPI...KPNA...AND KRKS.
STILL...ALL OTHER TERMINALS WILL REMAIN VFR. WE HAVE TRENDED BACK ON
LOWER CIGS AND VSBYS AS THE BEST ENERGY STAYS NORTH OF THIS REGION.
BIGGER ISSUE EAST OF THE DIVIDE WILL BE GUSTY SOUTH TO WEST WIND
AHEAD OF THE COLD FRONT. SURFACE WIND OF 15-20KTS WILL BE COMMON
WITH GUSTS 25-35 KTS AT MANY TERMINALS. WINDS WILL DECREASE AND
BECOME MORE WEST TO NORTHWEST AFTER 00Z/WED AS THE TROUGH PUSHES
EAST THROUGH THE FORECAST AREA. THE EXCEPTION WILL BE KRIW WHERE
FAVORABLE NORTHWEST FLOW WILL PRODUCE A PERIOD OF POST-TROUGH WIND
15-25KTS THROUGH 06Z/WED.


.FIRE WEATHER...

THE UPPER LEVEL HIGH PRESSURE RIDGE THAT HAS BROUGHT MILD...DRY
AND STABLE CONDITIONS TO WESTERN AND CENTRAL WYOMING OVER THE WEEKEND
HAS SHIFTED EAST INTO THE GREAT PLAINS AS A FAST MOVING PACIFIC
TROUGH MOVES INLAND INTO THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA.  THIS WILL BRING INCREASING SOUTHWEST FLOW
ALOFT...INSTABILITY AND MOISTURE TO THE AREA AS THE TROUGH
APPROACHES WESTERN WYOMING.  WINDS WILL INCREASE TONIGHT AND TUESDAY
BECOMING WINDY OVER AND NEAR THE MOUNTAINS AND THROUGH THE WIND
CORRIDOR. SOME GUSTS TO 45 MPH CAN BE EXPECTED FROM ROCK SPRINGS
THROUGH SOUTH PASS TO CASPER...AND IN THE CODY FOOTHILLS. SHOWERS
AND CLOUDS WILL INCREASE OVER THE WEST LATER TONIGHT AND BECOME MORE
WIDESPREAD OVER THE MOUNTAINS THROUGH TUESDAY. ISOLATED
THUNDERSTORMS CANNOT BE RULED OUT WITH MARGINAL INSTABILITY AND
INCREASING JET DYNAMICS OVER THE AREA. RELATIVE HUMIDITY WILL
INCREASE ALONG WITH THE CLOUDS AND SHOWERS. THE LOWER ELEVATIONS
EAST OF THE CONTINENTAL DIVIDE SHOULD REMAIN DRY BUT WILL SEE MORE
CLOUD COVER BRINGING SOME COOLING.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...BRANHAM
AVIATION...CNJ
FIRE WEATHER...C.BAKER









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