Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 200902
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
302 AM MDT MON APR 20 2015

.SHORT TERM...MONDAY THROUGH WEDNESDAY

AT AROUND 2 AM...WE STILL HAVE A COUPLE OF STRAY SHOWERS ACROSS THE
AREA ALTHOUGH COVERAGE CONTINUES TO DECREASE AND SHOULD BE JUST ABOUT
COMPLETELY GONE BY FIRST LIGHT. MOST OF THE REGION SHOULD HAVE A
WARMER AND MILDER DAY AS HEIGHTS RISE A BIT AS RIDGING STARTS TO
BUILD INTO THE AREA. THERE MAY BE JUST ENOUGH INSTABILITY ACROSS THE
MOUNTAINS FOR A FEW SHOWERS BUT THESE LOOK TO BE FEW AND FAR
BETWEEN. ALL IN ALL...A FAIRLY QUIET START TO THE WORKWEEK. A BIT OF
ENERGY STILL MAY BRING A FEW SHOWERS TO SOUTHWESTERN WYOMING THIS
EVENING BEFORE MOVING OUT OF THE AREA. CONTINUITY HAD THIS
REPRESENTED FAIRLY WELL SO WE MADE FEW CHANGES.

TEMPERATURES SHOULD CONTINUE TO RISE TUESDAY AS RIDGING BUILDS.
HOWEVER...INSTABILITY WILL INCREASE A BIT AS A SHORTWAVE APPROACHES
FROM THE WEST. THIS...COMBINED WITH SOME HIGH ELEVATION HEAT
SOURCE...MAY BE ENOUGH TO TOUCH OF SOME SHOWERS...MAINLY ACROSS THE
WESTERN MOUNTAINS. MOST OF THE LOWER ELEVATIONS SHOULD STAY LARGELY
RAIN FREE AS 700 MILLIBAR FLOW IS FAIRLY WEAK FOR MOST AREAS. MOST
OF THESE SHOWERS SHOULD END WITH THE LOSS OF DAYTIME HEATING WITH
MAINLY DRY CONDITIONS FOR LATE TUESDAY NIGHT AND INTO WEDNESDAY.

AS FOR WEDNESDAY...IT LOOKS LIKE MORE OF THE SAME. ANOTHER SHORTWAVE
HEADS TOWARD THE AREA WITH A BIT MORE MOISTURE FLOWING IN AHEAD OF
IT. AS A RESULT...IT LOOKS LIKE ANOTHER ROUND OF SHOWERS. WITH A BIT
MORE INSTABILITY...CONTINUITY ALSO INCLUDED THUNDER SO WE KEPT THAT
AS WELL.


.LONG TERM...THURSDAY THROUGH MONDAY

COMPLEX LONG TERM FORECAST WITH SPLITTING PACIFIC ENERGY MOVING
ACROSS THE WEST/ROCKIES...AS WELL AS A QUASI-STATIONARY FRONTAL
BOUNDARY EAST OF THE DIVIDE INTO THE HIGH PLAINS THUR-SAT.
CURRENTLY...MODELS SHOW THE BULK OF THE ENERGY HEADING NORTH OR
SOUTH OF THE FORECAST AREA. THE BEST INSTABILITY APPEARS TO BE
THURSDAY...AS A STRONG SOUTHERN PIECE OF ENERGY BEGINS TO
TRANSLATE ACROSS THE SOUTHERN ROCKIES. WILL MENTION THUNDERSTORMS
ACROSS THE ENTIRE AREA...AS BOTH THE ECMWF AND GFS ARE SHOWING
STEEP LAPSE RATES AND LIFTED INDEX VALUES OF -2 TO -4 OVER THE
AREA. THE MAIN ENERGY FROM THE SOUTHERN SYSTEM SHOULD PUSH INTO
THE SOUTH CENTRAL PLAINS FRIDAY...BUT SOME NORTHERN STREAM ENERGY
SHOULD KEEP A DECENT CHANCE OF SHOWERS WITH POSSIBLY A FEW
THUNDERSTORMS OVER THE WEST/SOUTH...AS INSTABILITY REMAINS BUT IS
PROGGED TO BE MUCH WEAKER. MODELS THEN SHOW THE NORTHERN STREAM
ENERGY REMAINING OVER THE NORTHERN ROCKIES SATURDAY WITH A
CONTINUED CHANCE OF CONVECTION. HAVING SAID THAT...MODELS HAVE
TRENDED A BIT DRIER SATURDAY.

GLOBAL MODELS THEN TRY TO BRING A MORE STOUT TROUGH INTO THE WEST
EARLY NEXT WEEK...WITH UPSTREAM RIDGING OVER THE ROCKIES/PLAINS
DEVELOPING. ENOUGH MOISTURE AND WEAK WAVES MOVING THROUGH THE
RIDGE...AS WELL AS SOME ENSEMBLES SUPPORTING ANOTHER SPLITTING
TROUGH...WILL KEEP THE CONTINUED MENTION OF AT LEAST ISOLATED
CONVECTION IN THE FORECAST. FOR NOW...WILL KEEP ISOLATED POPS FOR
SUNDAY/MONDAY MAINLY CONFINED TO THE WEST.

TEMPERATURES IN THE LONG TERM ARE EXPECTED TO BE SEASONAL TO
SLIGHTLY ABOVE AVERAGE.

&&

.AVIATION.../12Z ISSUANCE/

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

SCATTERED SHOWERS WILL DEVELOP THIS AFTERNOON OVER OR ALONG THE
ABSAROKA AND WIND RIVER MOUNTAINS. AN ISOLATED THUNDERSTORM IS
POSSIBLE FROM 21Z UNTIL 03Z. ISOLATED SHOWERS WILL OCCUR FROM NEAR A
KCOD TO KLND LINE THIS AFTERNOON INTO THE EARLY EVENING. EXPECT
OCCASIONAL MOUNTAIN OBSCURATION THIS AFTERNOON INTO THE EVENING.
MOST OF THE SHOWERS WILL DISSIPATE BY 06Z TUE. VFR CONDITIONS WILL
PREVAIL AT THE TERMINAL SITES THROUGH THE PERIOD.

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

SCATTERED SHOWERS WILL DEVELOP IN SOUTHWEST WY AFTER 19Z AND
CONTINUE UNTIL 03Z WITH AN ISOLATED THUNDERSTORM POSSIBLE. TERMINAL
SITES MAY SEE A BRIEF SHOWER IN THE SOUTHWEST. EXPECT OCCASIONAL
MOUNTAIN OBSCURATION THIS AFTERNOON INTO THE EVENING. KJAC AIRPORT
LOOKS TO MISS THE SHOWER ACTIVITY THIS AFTERNOON AND EARLY EVENING.
VFR CONDITIONS WILL PREVAIL AT THE TERMINAL SITES THROUGH THE PERIOD.

&&

.FIRE WEATHER...

THERE WILL BE A CHANCE FOR SHOWERS OFF AND ON THIS WEEK BUT WITH A
LOW CHANCE OF ANY WETTING RAIN UNTIL LATE IN THE WEEK WHEN ANOTHER
LARGE PACIFIC SYSTEM COULD BE MOVING IN AND STAYING FOR A WHILE.
OTHERWISE THERE ARE NO MAJOR WIND EVENTS OR SIGNIFICANT LIGHTNING
EPISODES ON THE HORIZON.

&&

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

&&

$$

SHORT TERM...HATTINGS
LONG TERM...WM
AVIATION...AR
FIRE WEATHER...HATTINGS







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