Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 170159
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
758 PM MDT SAT AUG 16 2014

.SHORT TERM...TONIGHT THROUGH SUNDAY

AN AREA OF LOW PRESSURE WILL HELP TO FLATTEN THE RIDGING OVER THE
FORECAST AREA THIS EVENING...BRINGING SOME ZONAL FLOW. THIS FLOW
PATTER WILL GENERALLY REMAIN DRY...THOUGH A FEW SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE DURING THE EARLY EVENING
HOURS...MAINLY ACROSS EXTREME NORTHERN WYOMING.

THE AREA OF LOW PRESSURE HELPING TO FLATTEN THE RIDGE WILL MOVE
FURTHER EAST THROUGH SUNDAY...ALLOWING SOME RETURN OF NORTHWEST FLOW
TO THE FORECAST AREA. THIS FLOW WILL PERMIT A BIT MORE MOISTURE TO
RETURN TO THE AREA...WITH A FEW SHOWERS AND THUNDERSTORMS
POSSIBLE...MAINLY OVER THE CENTRAL MOUNTAINS. SLIGHTLY COOLER
TEMPERATURES EXPECTED ON SUNDAY...THOUGH NOT MUCH VARIANCE FROM
THOSE TEMPERATURES EXPERIENCED TODAY.

GUSTY WIND WILL REMAIN THROUGH THE EARLY EVENING HOURS...ESPECIALLY
ACROSS SOUTHERN WYOMING. LIGHT WIND EXPECTED THROUGH THE OVERNIGHT
HOURS...WITH A RETURN OF GUSTY WIND POSSIBLE BY EARLY SUNDAY
AFTERNOON.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

HIGH PRESSURE RIDGE ALOFT WILL EXTEND NORTH FROM FOUR CORNERS HIGH
SUNDAY NIGHT WITH LIMITED MOISTURE IN WESTERLY FLOW INTO THE WESTERN
MOUNTAINS. MONDAY THE RIDGE ALOFT BEGINS TO SHIFT EAST WITH A SLIGHT
INCREASE IN SUBTROPICAL MONSOON MOISTURE ADVECTING NORTH INTO
WESTERN WYOMING AS A PACIFIC LOW PRESSURE TROUGH MOVES INLAND INTO
THE PACIFIC NORTHWEST.  THERE WILL BE INCREASED SHOWER AND
THUNDERSTORM ACTIVITY MAINLY IN THE WESTERN MOUNTAINS IN THE
AFTERNOON AND EVENING. TUESDAY THE PACIFIC TROUGH WILL DEEPEN AND
SHIFT EAST PROVIDING A BETTER SHEAR ENVIRONMENT ALONG WITH COLD AIR
ADVECTION ALOFT HELPING TO DESTABILIZE THE AIR MASS IN THE AFTERNOON
FOR A CONTINUATION OF INCREASED CONVECTION.  OVERALL TEMPERATURES
WILL COOL. THE PACIFIC TROUGH WILL CONTINUE TO DEEPEN AND SHIFT EAST
INTO THE NORTHERN ROCKIES WITH INCREASED SOUTHWEST FLOW ALOFT ON
WEDNESDAY. WITH A CONTINUATION OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS MOST NUMEROUS IN THE NORTHWEST. AS THE PACIFIC TROUGH
MOVES WAST ACROSS MONTANA AND WYOMING...COLDER AIR WILL CONTINUE TO
COOL TEMPERATURES WITH CONVECTION MAINLY OVER THE NORTHWEST
MOUNTAINS.  AS THE PACIFIC TROUGH MOVES EAST INTO THE NORTHERN
PLAINS...A HIGH PRESSURE RIDGE WILL SURGE NORTH FROM THE DESERT
SOUTHWEST WITH A RETURN OF THE SUBTROPICAL MONSOON MOISTURE FRIDAY
AND SATURDAY WITH INCREASED SHOWERS AND THUNDERSTORMS WITH SLIGHT
WARMING WITH SOUTH SOUTHWEST FLOW ALOFT.  MODELS START OUT IN FAIR
AGREEMENT THEN START TO DIFFER IN THE STRENGTH AND POSITION OF THE
PACIFIC TROUGH.  PREFER THE MORE PROGRESSIVE GFS OVER THE MORE
CLOSED LOW SCENARIO WITH THE ECMWF AT THIS TIME.

&&

.AVIATION.../00Z ISSUANCE/

WIDESPREAD VFR CONDITIONS EXPECTED ACROSS THE FORECAST AREA
THROUGH 18Z. A FEW SHOWERS OR THUNDERSTORMS MAY BE PRESENT ACROSS
THE FAR NORTHERN REACHES OF THE FORECAST AREA THROUGH
02Z...INFLUENCING TURBULENCE OVER ANY IMPACTED FLIGHT PATHS. A
SLIGHT SURGE OF MOISTURE ANTICIPATED AFTER 18Z SUNDAY...WHICH WILL
INCREASE CLOUD COVER ACROSS MUCH OF THE AREA. A FEW SHOWERS WILL BE
POSSIBLE...MAINLY OVER THE CENTRAL MOUNTAINS. ADDITIONALLY...A FEW
OTHER LOCATIONS WILL SEE SOME INCREASED WIND AFTER 18Z...MAINLY
ACROSS THE SOUTH AND EAST.

&&

.FIRE WEATHER...

GUSTY WIND...DRY CONDITIONS...AND WARM TEMPERATURES WILL LINGER INTO
THE EARLY EVENING HOURS ACROSS SOUTHERN WYOMING. SOME GUSTY WIND
WILL BE POSSIBLE ACROSS ADDITIONAL PORTIONS OF THE FORECAST
AREA...BUT HUMIDITY AND WIND ARE NOT EXPECTED TO BE CRITICAL FOR A
SIGNIFICANT AMOUNT OF TIME. WIND WILL RELAX DURING THE EVENING
HOURS...WITH LIGHT WIND EXPECTED OVERNIGHT. SLIGHTLY COOLER
TEMPERATURES ANTICIPATED MONDAY ACROSS THE AREA...WITH GENERALLY
LIGHT WIND. WIND MAY AGAIN INCREASE DURING THE AFTERNOON
HOURS...ESPECIALLY OVER NATRONA AND SWEETWATER COUNTIES. THIS
SCENARIO MAY NEED TO BE MONITORED THIS EVENING.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

&&

$$

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








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