Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 030510
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1110 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.../06Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

A WEAK COLD FRONT WILL PUSH SOUTH ACROSS THE AREA...STALLING OUT
ALONG THE DIVIDE BY AROUND 15Z SUNDAY. IN WAKE OF THIS
FRONT...EXPECT A NORTHERLY TO EASTERLY SURFACE FLOW THRU SUNDAY
EVENING. ALTHOUGH BOUNDARY LAYER MOISTURE WILL INCREASE IN WAKE OF
THE FRONT...LOW CLOUDS ARE NOT EXPECTED SUNDAY MORNING. THE AIR MASS
WILL BE RELATIVELY STABLE FOR MUCH OF THE DAY...BUT WILL BEGIN TO
BECOME SLIGHTLY UNSTABLE AFTER 21Z SUNDAY WITH PEAK HEATING AND SOME
CONVECTION IS POSSIBLE ESPECIALLY CLOSER TO THE DIVIDE. WILL MENTION
VCTS AT KLND AND KCPR...BUT ONLY HAVE VCSH AT TERMINALS FARTHER
NORTH. THIS CONVECTION SHOULD WEAKEN BY AROUND 03Z MONDAY...BUT SOME
ISOLATED ACTIVITY COULD LINGER PAST 06Z MONDAY.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

A SLIGHTLY UNSTABLE ATMOSPHERE WITH ADEQUATE MOISTURE WILL ALLOW FOR
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE
AREA...MAINLY SUNDAY AFTERNOON AND EVENING. INVERTED V
SOUNDINGS...STEEP LAPSE RATES AND COOL TEMPERATURES ALOFT SUGGEST
STRONG OUTFLOW WINDS AND SMALL HAIL WILL BE THE MAIN HAZARDS. ENOUGH
COVERAGE TO MENTION VCTS AT ALL TERMINALS DURING THE AFTERNOON AND
EVENING. THE CONVECTION WILL WEAKEN BY AROUND 03Z MONDAY...BUT SOME
ACTIVITY COULD LINGER PAST 06Z MONDAY.

&&

.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...WM
FIRE WEATHER...C.BAKER









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