Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 022048
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
248 PM MDT SAT MAY 2 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY

ZONAL FLOW WILL BE OVER THE AREA THROUGH SUNDAY WITH WEAK LOW
PRESSURE TROUGHS IN THE NORTHERN BRANCH OF THE FLOW AND SUBTROPICAL
MOISTURE MOVING UP FROM THE GREAT BASIN IN THE SOUTHERN BRANCH
OF THE FLOW.  DIURNALLY DRIVEN SCATTERED SHOWERS WITH ISOLATED
THUNDERSTORMS WILL RESULT LASTING INTO THE MID EVENING HOURS
AND REFORMING LATE SUNDAY MORNING AND INCREASING THROUGH THE
AFTERNOON. CLOUD COVER AND SCATTERED PRECIPITATION WILL HAVE A
COOLING EFFECT WITH SLIGHT COOLING TONIGHT AND GREATER COOLING
ON SUNDAY.  WITH MODERATE FLOW ALOFT AND CONVECTIVE CELLS MOVING
25 TO 30 MPH...WIND GUSTS TO 45 MPH WILL ACCOMPANY THE THUNDERSTORMS
ALONG WITH SMALL HAIL. MOUNTAIN AREAS ABOVE 9500 FEET SHOULD SEE
SOME LIGHT SNOW/GRAUPEL...ESPECIALLY THIS EVENING.  THE COVERAGE
OF SHOWERS AND THUNDERSTORMS IS EXPECTED TO INCREASE SUNDAY
AFTERNOON.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

SOUTHERLY PUSHES OF MOISTURE WILL BRING AFTERNOON SHOWERS AND
THUNDERSTORMS THE NEXT FEW DAYS UNDER A INCREASINGLY SOUTHWEST FLOW.
COVERAGE OF STORMS WILL INCREASE THROUGH THE AFTERNOON...WITH SOME
OF THE BEST COVERAGE ANTICIPATED ACROSS SOUTHWESTERN WYOMING. AN
AREA OF LOW PRESSURE IS STILL EXPECTED TO IMPACT THE PACIFIC
NORTHWEST TUESDAY AFTERNOON...HELPING TO KEEP SHOWER ACTIVITY ACROSS
THE AREA EARLY NEXT WEEK

THIS AREA OF LOW PRESSURE WILL DIVE SOUTH THROUGH THE WEEK...LANDING
OVER THE DESERT SOUTHWEST BY THURSDAY EVENING. THIS WILL LEAVE A
STRONG SOUTH-SOUTHWESTERLY FLOW ACROSS THE AREA THROUGH MUCH OF NEXT
WEEK...AGAIN ENCOURAGING SHOWER AND THUNDERSTORM ACTIVITY.

THE MOVEMENT OF THE AREA OF LOW PRESSURE VARIES A BIT DEPENDING ON
WHICH MODEL IS USED TO DICTATE ITS PATH...THOUGH BOTH MODELS
EVENTUALLY PUSH THE SYSTEM NORTH OVER NORTHERN UTAH BY SATURDAY
MORNING. STORM COVERAGE RELATING TO THIS SYSTEM DRASTICALLY
INCREASES THROUGH SATURDAY AFTERNOON AND EVENING....WITH BASICALLY
THE ENTIRETY OF THE FORECAST AREA INCLUDED IN FORECASTED STORM
COVERAGE. THE OVERALL ADVANCEMENT OF THIS SYSTEM WILL DRAG SOME
COOLER TEMPERATURES ACROSS THE FORECAST AREA. HOWEVER...TEMPERATURES
WILL GENERALLY REMAIN SEASONABLY MILD THROUGH THE FORECAST PERIOD.

&&

.AVIATION.../00Z ISSUANCE/

VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD AT THE AIRPORTS.
BRIEF MVFR CONDITIONS COULD IMPACT THE SOUTHERN AND WESTERN AIRPORTS
AS SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MOVE THROUGH THROUGH
THE EARLY EVENING HOURS. A PACIFIC TROUGH WILL MOVE THROUGH
WESTERN AND CENTRAL WYOMING THIS EVENING COMBINING WITH
SUBTROPICAL MOISTURE MOVING NORTH AND EAST FROM THE GREAT BASIN.
THE COMBINATION WILL PRODUCE SCATTERED RAIN SHOWERS...POSSIBLE
SNOW ABOVE 9500 FEET...AND ISOLATED THUNDERSTORMS OVER THE
SOUTHWEST AND WESTERN MOUNTAINS WITH WIND GUSTS TO 45KTS THROUGH
06Z SUNDAY. THE HIGHER MOUNTAINS WILL BE OBSCURED LOCALLY WITH
THE HEAVIER SHOWERS AND THUNDERSTORMS. THE COVERAGE IS NOT
EXPECTED TO BE WIDESPREAD ENOUGH TO SINGLE OUT ANY AIRPORT FOR
LOWER CEILINGS AND VISIBILITY.  ANOTHER PACIFIC TROUGH WITH MORE
MOISTURE COMING UP FROM THE GREAT BASIN WILL PRODUCE INCREASED
CLOUDS AND SHOWER ACTIVITY IN THE SOUTHWEST AND WESTERN MOUNTAINS
FROM 15Z TO 18Z SUNDAY WITH ISOLATED THUNDERSTORMS AFTER 18Z.

&&

.FIRE WEATHER...

ZONAL FLOW WILL BE OVER THE AREA THROUGH SUNDAY WITH WEAK LOW
PRESSURE TROUGHS IN THE NORTHERN BRANCH OF THE FLOW AND SUBTROPICAL
MOISTURE MOVING UP FROM THE GREAT BASIN IN THE SOUTHERN BRANCH
OF THE FLOW.  DIURNALLY DRIVEN SCATTERED SHOWERS WITH ISOLATED
THUNDERSTORMS WILL RESULT LASTING INTO THE MID EVENING HOURS
AND REFORMING LATE SUNDAY MORNING AND INCREASING THROUGH THE
AFTERNOON. CLOUD COVER AND SCATTERED PRECIPITATION WILL HAVE A
COOLING EFFECT WITH SLIGHT COOLING TONIGHT AND GREATER COOLING
ON SUNDAY.  WITH MODERATE FLOW ALOFT AND CONVECTIVE CELLS MOVING
25 TO 30 MPH...WIND GUSTS TO 45 MPH WILL ACCOMPANY THE THUNDERSTORMS
ALONG WITH SMALL HAIL. MOUNTAIN AREAS ABOVE 9500 FEET SHOULD SEE
SOME LIGHT SNOW/GRAUPEL...ESPECIALLY THIS EVENING.  THE COVERAGE
OF SHOWERS AND THUNDERSTORMS IS EXPECTED TO INCREASE SUNDAY
AFTERNOON. WITH STRONG CONVECTIVE MIXING AND MODERATE FLOW ALOFT
GOOD OR BETTER SMOKE DISPERSAL IS EXPECTED SUNDAY AFTERNOON.

&&

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

$$

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







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