Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 272040
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
240 PM MDT SAT JUN 27 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY

NORTHWEST FLOW ALOFT WILL CONTINUE WITH HIGH PRESSURE RIDGE
TO THE WEST OVER GREAT BASIN NORTH INTO NORTHERN ROCKIES.
SUBTROPICAL PACIFIC MOISTURE TRANSPORTED NORTH ON WEST SIDE
OF RIDGE STARTING TO TOP THE RIDGE AND MOVE INTO NORTHWEST FLOW
SPREADING OVER WESTERN WYOMING. TEMPERATURES HAVE WARMED AND WITH
HEATING...AIR MASS BEGINNING TO DESTABILIZE OVER MOUNTAINS WITH
SHOWERS AND ISOLATED THUNDERSTORMS STARTING TO DEVELOP. CONVECTION
WILL HAVE HARDER TIME CONTINUING OVER THE MORE STABLE AIR MASSES
IN THE BASINS. MORE MOISTURE WILL MOVE IN ON SUNDAY WITH REPEAT
OF MOSTLY MOUNTAIN SHOWERS AND THUNDERSTORMS WITH WARMING
CONTINUING.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

THE CANADIAN COLD FRONT HAS MADE IT ALMOST TO THE DIVIDE. WHEN THE
SHORTWAVE TRAVELING EAST ACROSS MONTANA EJECTED THE FRONT TOWARD
WYOMING EARLIER THIS EVENING...THUNDERSTORM OUTFLOW WINDS
ORIGINATING IN MONTANA COMBINED WITH THE FRONT AND PRODUCED SHARP
SFC PRESSURE RISES THAT RESULTED IN STRONG 62 MPH NORTH WINDS AT
BYG.

FLAT HIGH PRESSURE WILL BUILD INTO THE AREA TODAY. AFTER THIS
EVENINGS FROPA...JOHNSON COUNTY WILL BE 5 TO 10 DEGREES COOLER TODAY
THAN SUNDAY AND JUST A COUPLE OF DEGREES COOLER ELSEWHERE EAST OF
THE DIVIDE WITH NOT MUCH CHANGE FROM SUNDAY WEST. NW WINDS WILL BACK
TO THE WEST...WEST OF THE DIVIDE TODAY WITH LIGHTER NE TO EAST WINDS
EAST. WITH THE HIGHER DEW POINTS AND CAPE EXPECTED TODAY IN NORTHERN
AND NORTHEAST WY AS THE SFC FRONT RETREATS NORTHEAST...A FEW
 COULD POP IN THE FAR NORTH AND NE LATER TODAY.

THEN ON TUESDAY...TEMPERATURES WILL WARM A COUPLE OF DEGREES IN THE
CENTRAL AND SOUTH BUT LOWER A COUPLE OF DEGREES DUE TO MORE CLOUDS
AND POSSIBLE T STORMS FROM ANOTHER APPROACHING COOL FRONT IN THE
NORTH AND NORTHEAST EJECTED BY AN EASTBOUND VORT LOBE. THESE
THUNDERSTORMS WILL FIRST FORM IN FAR NORTHERN WY AND WILL SLIDE
SOUTHEAST TOWARD NATRONA COUNTY TUESDAY NIGHT AS A THETA E RIDGE
ESTABLISHES ITSELF IN THOSE AREAS AS IT EXTENDS IN FROM THE
SOUTHEAST. THESE SHOWERS WILL LIKELY PERSIST IN JOHNSON COUNTY
WELL INTO TUESDAY NIGHT.

THEN ON WEDNESDAY...TEMPS WILL COOL SLIGHTLY BEHIND THIS NEXT FRONT
IN THE NORTH AND EAST BUT WILL LIKELY BE IN THE LOW 90S IN THE WIND
RIVER BASIN WITH TEMPS ALSO REMAINING THE SAME OR WARMING A COUPLE
OF DEGREES ELSEWHERE. A FEW THUNDERSTORMS WILL DEVELOP EAST OF THE
DIVIDE AS ANOTHER WEAK IMPULSE IN THE WESTERLY FLOW BISECTS TUESDAY
NIGHTS SFC BOUNDARY THAT WILL STILL BE DRAPED NW TO SE...EAST OF THE
DIVIDE.

&&

.AVIATION.../00Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL AT THE AIRPORTS ACROSS THE AREA
THROUGH 00Z MONDAY. ISOLATED AFTERNOON AND EVENING (00Z-04Z)
THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS AND PUSH SOUTHEAST
INTO ADJACENT FOOTHILLS BEFORE QUICKLY DISSIPATING. THE BEST SHOT
FOR THIS ISOLATED CONVECTION APPEARS TO BE OVER THE SOUTHERN
ABSAROKA AND SOUTHERN WIND RIVER MTS. THE MAIN HAZARD FROM THIS
ACTIVITY WILL BE STRONG OUTFLOW WINDS AND SMALL HAIL. INCREASED
MID AND HIGH CLOUDS WILL REMAIN OVER THE WEST TONIGHT. ANOTHER
ROUND OF CONVECTION OVER THE MOUNTAINS EXPECTED SUNDAY AFTERNOON.
THE LIMITED COVERAGE OF THUNDERSTORMS PRECLUDE ANY MENTION
TERMINAL FORECASTS AT THIS TIME.

&&

.FIRE WEATHER...

NORTHWEST FLOW ALOFT WILL CONTINUE WITH HIGH PRESSURE RIDGE
TO THE WEST OVER GREAT BASIN NORTH INTO NORTHERN ROCKIES.
SUBTROPICAL PACIFIC MOISTURE TRANSPORTED NORTH ON WEST SIDE
OF RIDGE STARTING TO TOP THE RIDGE AND MOVE INTO NORTHWEST FLOW
SPREADING OVER WESTERN WYOMING. TEMPERATURES HAVE WARMED AND WITH
HEATING...AIR MASS BEGINNING TO DESTABILIZE OVER MOUNTAINS WITH
SHOWERS AND ISOLATED THUNDERSTORMS STARTING TO DEVELOP. CONVECTION
WILL HAVE HARDER TIME CONTINUING OVER THE MORE STABLE AIR MASSES
IN THE BASINS. MORE MOISTURE WILL MOVE IN ON SUNDAY WITH REPEAT
OF MOSTLY MOUNTAIN SHOWERS AND THUNDERSTORMS WITH WARMING
CONTINUING. MIXING HEIGHTS AND TRANSPORT WINDS WILL COMBINE FOR
VERY GOOD TO EXCELLENT SMOKE DISPERSAL THROUGH 20:00 THIS EVENING
AND AGAIN SUNDAY AFTERNOON.

&&

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

$$

SHORT TERM...C.BAKER
LONG TERM...LIPSON
AVIATION...C.BAKER
FIRE WEATHER...C.BAKER



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