Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 151708
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1108 AM MDT MON SEP 15 2014

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
THE LAST IN A SERIES OF GLANCES FROM DRY SHORTWAVES DIVING
SOUTHEAST ACROSS THE NORTHERN PLAINS DOWN THE BACK SIDE OF THE
EXITING MAIN TROUGH AND ON THE FRONT SIDE OF THE APPROACHING HIGH
PRESSURE RIDGE NOW ALONG THE PACIFIC COAST IS TAKING PLACE. EAST
WINDS BEHIND THE ASCT BACKDOOR DRY COOL FRONT HAVE ALREADY
DIMINISHED WITH THE LEADING EDGE OF THIS SURFACE BOUNDARY AS FAR
SOUTHWEST AS FARSON AT THE TIME OF THIS WRITING. TODAY AND TUESDAY
WILL FEATURE RATHER BENIGN PLEASANT FALL WEATHER AS THE RIDGE OF
HIGH PRESSURE RIDGE MAKES ITS WAY TO THE ROCKIES. AFTER ALL...WE
CANNOT COMPLETELY DISMISS FALL BEFORE WINTER ARRIVES. TEMPS WILL
STEADILY RISE THROUGH WEDNESDAY WITH HIGHS WAY UP IN THE MID 80S
AT THE LOWER ELEVATIONS EAST OF THE DIVIDE BY THEN AND WELL UP
INTO THE 70S WEST. THE PRESSURE GRADIENT WILL TIGHTEN TUESDAY
NIGHT AND WEDNESDAY ALONG WITH A RESULTING SURFACE LEE SIDE TROUGH
AS THE NEXT UPSTREAM TROUGH APPROACHES AND THE RIDGE FLATTENS
RESULTING IN INCREASED WINDS. SOME MID AND UPPER LEVEL MOISTURE
WILL MOVE IN WITH THE INCREASING SOUTHWEST FLOW WEDNESDAY ALONG
WITH WEAK INSTABILITY...JUST ENOUGH FOR SOME WEAK SPOTTY
CONVECTION OUT WEST.

.LONG TERM...THURSDAY THROUGH MONDAY
EVEN MORE SPLITTING IN THE UPCOMING TROUGH SHOWING UP IN THE
MODELS TONIGHT. SO MUCH SO...THAT IT`S QUESTIONABLE HOW MUCH
MOISTURE AND FORCING WE ACTUALLY GET ACROSS THE WEST AND SOUTH
FROM THIS SYSTEM. WE`LL PROBABLY GET THE BEST SUPPORT IN THE
SOUTHWEST AND FAR SOUTH WITH SOME SUPPORT IN THE FAR WEST AND
NORTH FROM THE DEFORMATION AND FRONTAL ZONE AS IT MOVES EAST
ACROSS THE AREA THURSDAY NIGHT INTO FRIDAY. WE END UP WITH THE A
LITTLE SUPPORT IN THE SOUTHWEST FROM THE NRN END OF THE SPLITTING
TROUGH TO OUR SW AND A LITTLE ACROSS THE NORTH FROM THE NORTHERN
PIECE OF THE TROUGH...OR WHAT`S LEFT OF IT. STILL MAY BE ENOUGH
DAYTIME HEATING AND FRONTAL FORCING FOR SOME LATE DAY
THUNDERSTORMS IN THE WEST WITH THIS TROUGH BUT HARD TO GET TOO
EXCITED ANYMORE WITHOUT ANY SIGNIFICANT MOISTURE SURGE NWD. MINIMAL
ODILE MOISTURE WILL LIKELY GET ENTRAINED. MOST OF IT WILL STAY TO
THE SOUTH. OTHERWISE...RIDGE MOVES BACK IN FOR THE WEEKEND ALBEIT
WITH SURFACE HIGH NEARBY TO KEEP US FROM FULLY MIXING AND LIKELY
NOT REACHING OUR MAX POTENTIAL BASED ON H7 TEMPS. HUGE DISCREPANCIES
AT THE END OF THE PERIOD AS THE ECMWF TAKES THE SRN PIECE OF OUR
SPLITTING TROUGH AND LIFTS IT NE ACROSS US LATE SUNDAY INTO MONDAY
WHILE THE GFS KEEPS IT WELL SOUTH WITH A WARM RIDGE OVERHEAD. A
FEW GFS ENSEMBLE MEMBERS SUPPORT THE OP ECMWF BUT MOST DO NOT. THE
12Z ECMWF ENSEMBLE MEMBERS SUPPORTED THE OP GFS RIDGE. NEIGHBORS
TO THE WEST AND SOUTH HAVE SOME POPS TO HEDGE TOWARDS THE REMNANT
UPPER GETTING CLOSE SO WILL HAVE JUST SOME ISOLATED POPS IN THE
FAR SOUTH LATE SUNDAY AND IN AND NEAR THE MOUNTAINS OF THE FAR
WEST AND SOUTH MONDAY. OTHERWISE...DRY.

&&

.AVIATION.../18Z ISSUANCE/
VFR CONDITIONS WILL PREVAIL THROUGH 18Z TUESDAY. ISOLATED SHOWERS
OR STORMS WILL OCCUR NEAR THE FAR SOUTHERN WYOMING BORDER FROM 21Z
MON UNTIL 02Z TUE. THE ACTIVITY WILL SHOULD SOUTH OF THE KRKS
AIRPORT. ISOLATED CONVECTION MAY OCCUR NEAR THE WESTERN MOUNTAINS ON
TUESDAY BUT WILL OCCUR AFTER 18Z.

&&

.FIRE WEATHER...
A BUILDING AREA OF HIGH PRESSURE WILL REMAIN OVER THE AREA FOR THE
NEXT FEW DAYS. THE HIGH PRESSURE SYSTEM WILL KEEP WARMING
TEMPERATURES AND DRY CONDITIONS PRESENT WITH LITTLE WIND EXPECTED
THROUGH AT LEAST TUESDAY. THE CHANCES OF AFTERNOON SHOWERS OR
THUNDERSTORMS WILL INCREASE FOR THE LATTER HALF OF THE WEEK
BEGINNING WEDNESDAY AFTERNOON AS THE NEXT UPSTREAM TROUGH APPROACHES.
WINDS WILL INCREASE BY TUESDAY NIGHT OR WEDNESDAY AS WELL.

&&

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

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...HATTINGS
FIRE WEATHER...LIPSON











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