Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 172218 CCA
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
254 PM MDT SUN AUG 17 2014

.SHORT TERM...TONIGHT THROUGH MONDAY

A FEW SHOWERS HAVE POPPED UP ON RADAR THIS AFTERNOON. SHOWER
ACTIVITY IS NOT ANTICIPATED TO BE LONG LIVED...WITH A FEW ISOLATED
SHOWERS AND THUNDERSTORMS POSSIBLE ACROSS THE SOUTHERN HALF OF THE
FORECAST AREA.

RELATIVELY QUIET CONDITIONS THROUGH THE OVERNIGHT HOURS UNDER
RETURNING HIGH PRESSURE. BUILDING NORTHWEST FLOW OVER THE FORECAST
AREA TONIGHT AND TOMORROW MORNING WILL PERMIT THE ARRIVAL OF
ANOTHER SLUG OF MOISTURE MONDAY AFTERNOON. THIS AREA OF MOISTURE
LOOKS FAVORABLE TO GENERATE SOME AFTERNOON SHOWERS AND
THUNDERSTORMS...ESPECIALLY OVER NORTH- CENTRAL WYOMING.
INSTABILITY INCREASES DURING THE LATER AFTERNOON HOURS...RESULTING
IN THE POTENTIAL FOR SOME GUSTY WIND WITH ACTIVITY. OTHERWISE
LIGHT WIND IS EXPECTED THROUGH THE FORECAST PERIOD. SLIGHTLY
COOLER TEMPERATURES WILL BE FOUND DUE TO THE INCREASED CLOUD
COVER.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

HIGH PRESSURE RIDGE ALOFT WILL EXTEND NORTH FROM NEW MEXICO WITH
LIMITED MOISTURE IN WESTERLY FLOW INTO THE WESTERN MOUNTAINS. THE
RIDGE ALOFT WILL 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 WEST 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...THE MODELS DIFFER ON
WHETHER A HIGH PRESSURE RIDGE WILL SURGE NORTH FROM THE DESERT
SOUTHWEST WITH A RETURN OF THE SUBTROPICAL MONSOON MOISTURE BY
SUNDAY...WITH INCREASED SHOWERS AND THUNDERSTORMS WITH SLIGHT
WARMING WITH SOUTH SOUTHWEST FLOW ALOFT...OR WHETHER A SECOND
PACIFIC TROUGH WILL DEEPEN OVER THE NORTHERN ROCKIES WITH CONTINUED
COOLING AND SOME DRYING WITH NORTHWEST FLOW ALOFT.  HAVE GONE WITH
AN AVERAGE BETWEEN THE TWO POSSIBLE SOLUTIONS KEEPING SOME COOLING
IN PLACE AND GENERALLY KEEPING THE MONSOON MOISTURE OUT OF THE AREA
FOR THE TIME BEING.   MOUNTAIN AND HIGH VALLEY AREAS WILL HAVE THE
POTENTIAL FOR SOME FREEZING NIGHT TIME TEMPERATURES FRIDAY MORNING
THROUGH SUNDAY MORNING.


&&

.AVIATION.../00Z ISSUANCE/

A FEW HIGH TERRAIN SHOWERS MAY BE FOUND THIS EVENING...MAINLY ACROSS
NORTHERN WYOMING. ACTIVITY WILL TAPER OFF DURING THE EVENING
HOURS...WITH WIDESPREAD VFR CONDITIONS EXPECTED. A RETURNING SLUG OF
MOISTURE WILL INCREASE CLOUD COVER OVER MUCH OF THE AREA AFTER 12Z
MONDAY. ADDITIONALLY...AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE AFTER 18Z...WITH SOME ACTIVITY IMPACTING TERMINALS IN THE
BIG HORN AND WIND RIVER BASINS AFTER 21Z.

&&

.FIRE WEATHER...

GUSTY WINDS ACROSS CENTRAL AND SOUTHERN WYOMING WILL CONTINUE INTO
THE EARLY EVENING HOURS TONIGHT. THESE GUSTY WINDS WILL COMBINE WITH
LOW HUMIDITY TO CREATE DANGEROUS FIRE BEHAVIOR. WIND WILL RELAX
DURING THE EVENING HOURS...WITH HUMIDITIES ALSO EXPECTED TO REBOUND
OVERNIGHT. A PUSH OF MOISTURE WILL INCREASE CLOUD COVER OVER THE
AREA ON MONDAY...HELPING TO COOL TEMPERATURES AND INCREASE DAYTIME
HUMIDITY. INSTABILITY WILL BE PRESENT ACROSS THE AREA...HELPING TO
GENERATE SOME ISOLATED SHOWERS AND THUNDERSTORMS DURING THE
AFTERNOON HOURS. GUSTY WIND WILL BE THE PRIMARY THREAT ASSOCIATED
WITH STORM ACTIVITY. HUMIDITIES IN THE LOW TEENS WILL AGAIN BE
POSSIBLE ACROSS SOUTHERN WYOMING...BUT WIND IS NOT EXPECTED TO BE
SIGNIFICANT OUTSIDE OF STORM ACTIVITY. PERIODS OF AFTERNOON SHOWERS
AND THUNDERSTORMS WILL BE FOUND OVER THE NEXT FEW DAYS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING
WYZ279-280-283-289-300.

&&

$$

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







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