Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 200450
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1050 PM MDT SUN APR 19 2015

UPDATED FOR 06Z AVIATION DISCUSSION.

.SHORT TERM...TONIGHT THROUGH MONDAY (ISSUED AT 216 PM MDT)

COOL UNSTABLE NORTHWEST FLOW STICKS AROUND THROUGH THE NIGHT. A FEW
SHOWERS COULD CONTINUE INTO THE EVENING HOURS...MAINLY ALONG THE
DIVIDE BUT A FEW COULD STREAM OFF THE HIGHER ELEVATIONS AND INTO THE
BASINS...ESPECIALLY SOUTHEAST OF SOUTH PASS WITH A FEW MORE SHOWERS
POSSIBLE BETWEEN ROCK SPRINGS AND RAWLINS. OTHERWISE...RELATIVELY
LIGHT WINDS AND SEASONAL TEMPERATURES EXPECTED OVERNIGHT.

FOR MONDAY...MILDER AIR MOVES IN FROM THE WEST AS A RIDGE BUILDS
AHEAD OF THE NEXT SYSTEM. THERE COULD BE A FEW AFTERNOON SHOWERS
ACROSS SOUTHWEST WYOMING AS SOME MOISTURE STICKS AROUND AND
AFTERNOON HEATING DESTABILIZES THE AREA. OTHERWISE ANOTHER QUIET DAY
IS IN STORE FOR MUCH OF THE FORECAST AREA.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

DEVELOPING SPLITTING FLOW WILL DOMINATE MUCH OF THE PERIOD EXCEPT AT
THE BEGINNING AND POSSIBLY AT THE END OF THIS PERIOD. NW FLOW WILL
INITIALLY DOMINATE WITH WEAK RIPPLES DROPPING SE OVER AND EAST OF US
KEEPING HIGHER PRESSURE TO THE NE AND THE PERSISTENT WEAK FRONTAL
BOUNDARY ALONG AND EAST OF THE DIVIDE. CONVERGENCE ALONG THIS
BOUNDARY COMBINED WITH LIMITED MOISTURE AND DAYTIME HEATING WILL
ALLOW SHOWERS TO FORM OVER THE HIGHER TERRAIN AND TRY TO DRIFT OFF
THE MOUNTAINS...MAINLY ALONG THE BOUNDARY WHICH WILL REMAIN ALONG
THE DIVIDE AND SOUTH INTO THE RED DESERT. LITTLE CHANGE NEEDED TO
START THIS PERIOD MONDAY EVENING AS THIS IS WELL DEPICTED WITH SOME
REMAINING SHOWERS MAINLY OVER THE WCNTRL/SWRN MTNS AND CONVERGENCE
AREA. BOUNDARY WEAKENS SOME ON TUESDAY AND THUS WILL KEEP MORE OF
THE SHOWERS IN THE MOUNTAINS ALONG AND WEST OF THE DIVIDE.
CONDITIONS CHANGE WEDNESDAY WITH ANOTHER SEWD MOVING DISTURBANCE
REINFORCING OUR BOUNDARY ALONG THE DIVIDE AND THEN COMBINING WITH
APPROACHING SPLITTING TROUGH. IT`S ACTUALLY A COMBINATION OF A NEW
SPLITTING TROUGH COMING ON THE COAST WEDNESDAY KICKING OUT THE WEAK
TROUGH JUST OFF THE CA COAST NOW. SOME ADDITIONAL HEATING AND A
LITTLE ADDITIONAL MID LEVEL MOISTURE WILL LIKELY LEAD TO MORE
SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND WEST OF THE DIVIDE BY
WEDNESDAY AFTERNOON. MAYBE EVEN A FEW IN THE SW BY LATE MORNING.
FLOW IS VERY WEAK SO THEY WILL LIKELY STRUGGLE TO GET OFF THE
MOUNTAINS BUT OUR REINVIGORATED COLD FRONT WILL FOCUS SOME
SHOWERS/TSTMS AS IT MOVES BACK INTO THE RED DESERT AND UP AGAINST
THE DIVIDE. AS THIS INITIAL CA UPPER LOW PASSES TO THE SOUTH AND
THE SPLITTING TROUGH APPROACHES AND WEAKENS...IT WILL LIKELY LEAD TO
AN INCREASING CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS THURSDAY
AND FRIDAY. AS THIS SPLITTING TROUGH APPROACHES AND THE CA MOVES
SOUTH OF US...THERE IS SOME INDICATION OF RETURN FLOW MOISTURE
EDGING NWWD INTO SERN WYOMING. IT MAY NOT MAKE IT INTO OUR AREA BUT
IT`S WORTH MONITORING. NOT SURE THERE WILL BE MANY SHOWERS EAST OF
THE DIVIDE UNTIL FRIDAY BUT WILL LEAVE IN THE SLIGHT CHANCES WE HAVE
THURSDAY ALREADY. MODELS DIVERGE QUITE A BIT NEXT WEEKEND WITH THE
GFS LOSING OUR NEXT APPROACHING TROUGH IN THE MEAN RIDGE OVER US
WHILE THE GEM HANGS ONTO A WEAKENING SPLITTING TROUGH AND THE ECMWF
HAS A STRONGER WAVE PASSING ACROSS THE NORTH ON SATURDAY WITH A
WEAKER ONE SUNDAY. MOST LIKELY THERE WILL EITHER BE A WEAKENING
SHORTWAVE IN THE AREA OR A FLAT SHORTWAVE RIDGE WITH EXPECTED
TROUGHS OVER THE ERN PACIFIC AND EASTERN U.S. AND A GENERAL MEAN
RIDGE EXPECTED OVER OUR AREA. GOING FORECAST WEIGHTED TOWARD A
DISTURBANCE STILL IN THE FLOW SATURDAY WITH A DECREASING CHANCE OF
SHOWERS SUNDAY. WILL GIVE THIS ANOTHER CLOSE LOOK TOMORROW.

&&

.AVIATION.../06Z ISSUANCE/

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

SHOWERS WILL END BY 12Z. THEN SCATTERED SHOWERS WILL DEVELOP MONDAY
AFTERNOON OVER OR ALONG THE ABSAROKA AND WIND RIVER MOUNTAINS. AN
ISOLATED THUNDERSTORM IS POSSIBLE FROM 21Z MON UNTIL 03Z TUE.
ISOLATED SHOWERS WILL OCCUR FROM NEAR A KCOD TO KLND LINE MONDAY
AFTERNOON INTO EARLY EVENING. EXPECT OCCASIONAL MOUNTAIN OBSCURATION
MONDAY 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

ISOLATED SHOWERS WILL END BY 10Z FROM NEAR KJAC TO KRKS LINE. THEN
SCATTERED SHOWERS WILL DEVELOP IN SOUTHWEST WY AFTER 19Z MON UNTIL
03Z TUE WITH AN ISOLATED THUNDERSTORM POSSIBLE. TERMINAL SITES MAY
SEE A BRIEF SHOWER IN THE SOUTHWEST. EXPECT OCCASIONAL MOUNTAIN
OBSCURATION MONDAY AFTERNOON AND EARLY EVENING. KJAC AIRPORT LOOKS
TO MISS THE SHOWER ACTIVITY MONDAY AFTERNOON INTO THE 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...ALLEN
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...ALLEN






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