597  
FXUS65 KRIW 170830  
AFDRIW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RIVERTON WY  
230 AM MDT THU AUG 17 2017  
   
SHORT TERM
 
THURSDAY THROUGH SATURDAY NIGHT  
 
OVER THE NEXT FEW DAYS THE PATTERN REMINDS ME IN A WAY OF THE CLASSIC  
SONG "SPINNING WHEEL" BY BLOOD, SWEAT AND TEARS. ONE OF THE MOST  
FAMOUS VERSES IN THAT SONG IS "WHAT GOES UP, MUST COME DOWN." IN  
THIS CASE, WHAT WILL BE GOING DOWN INTO THE FIRST PART OF THE  
WEEKEND IS THE CHANCE OF CONVECTION. WE STILL HAVE A COUPLE OF  
SHOWERS OUT THERE THIS MORNING BUT THEY ARE LIGHT AND WILL BE GONE  
BY MORNING. THIS AFTERNOON A WEAK DISTURBANCE WILL BRUSH BY THE  
AREA TO THE NORTH AND EAST. IT COULD GET CLOSE ENOUGH TO BRING  
SOME ISOLATED CONVECTION TO PORTIONS OF THE NORTHERN MOUNTAINS AND  
MORE LIKELY IN JOHNSON COUNTY. OTHERWISE, WITH DRIER AIR MOVING  
INTO THE AREA A VAST MAJORITY OF THE AREA WILL BE DRY. FRIDAY AT  
THIS POINT LOOKS LIKE A TYPICAL LATE SUMMER DAY WITH PLENTY OF  
SUNSHINE AND MAINLY DRY CONDITIONS. BY SATURDAY, A BIT MORE HIGH  
LEVEL MOISTURE MAY CREEP INTO THE AREA FROM THE SOUTH BUT ANY  
SHOWERS WOULD HOLD OFF UNTIL SUNDAY.  
 
AND WHAT GOES UP WILL BE THE TEMPERATURES AS HEIGHTS AND  
THICKNESSES RISE. WITH BREEZY CONDITIONS DEVELOPING IN SOME AREAS,  
THIS WILL WARM TEMPERATURES BACK CLOSE TO SEASONAL AVERAGES TODAY.  
BY FRIDAY AND ESPECIALLY SATURDAY, ABOVE NORMAL TEMPERATURES WILL  
BE FOUND ACROSS THE ENTIRE AREA WITH SUMMER MAKING A RETURN. SOME  
OF THE WARMER SPOTS LIKE GREYBULL, WORLAND AND POSSIBLY CASPER  
COULD SEE HIGHS IN THE 90S BY THE FIRST PART OF THE WEEKEND.  
   
LONG TERM
 
SUNDAY THROUGH THURSDAY  
 
ECLIPSE OUTLOOK ON MONDAY...THE LATEST MEDIUM-RANGE MODEL RUNS  
HAVE TRENDED FASTER WITH A SHORTWAVE MOVING EASTWARD ACROSS THE  
NORTHERN ROCKIES INTO THE NORTHERN HIGH PLAINS SUNDAY NIGHT-MONDAY  
MORNING. ANY SHOWER ACTIVITY IS EXPECTED TO BE EAST OF THE AREA  
BY SUNRISE MONDAY WITH AN OVERALL CLEARING TREND. THE OTHER  
CONCERN IS A BAND OF POTENTIAL HIGH CLOUD COVER ALONG A  
DEFORMATION AREA ACROSS SOUTHERN/CENTRAL WYOMING. MODELS HAVE  
TRENDED FURTHER SOUTH OVERALL, AWAY FROM THE PATH OF TOTALITY WITH  
THIS HIGH LEVEL MOISTURE. HOPEFULLY, THESE TRENDS CONTINUE;  
HOWEVER, THESE TRENDS ARE NOT WELL ESTABLISHED AT THIS POINT. THE  
OTHER FACTOR FOR CLOUDS WILL BE SLIGHT INSTABILITY ALONG THE  
DIVIDE. AGAIN, THE OVERALL TREND HAS BEEN FAVORABLE HERE, LESS  
MOISTURE, AND INSTABILITY ACROSS NW WYOMING (JACKSON HOLE AND  
GRAND TETON NATIONAL PARK). THE BEST CHANCES OF LATE MORNING  
CUMULUS BUILDUPS AND AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE  
ACROSS THE WIND RIVER-SALT-WYOMING RANGES.  
 
BACKING UP A BIT TO SUNDAY (ECLIPSE EVE?), THE AFOREMENTIONED  
SHORTWAVE IS EXPECTED TO MOVE EAST ACROSS MONTANA, ENCOUNTERED  
THE BETTER MOISTURE AND INSTABILITY ALONG AND EAST OF A LEE SIDE  
SURFACE TROUGH THAT WILL BE ACROSS EASTERN WYOMING. ANY SHOWERS  
AND THUNDERSTORMS ACROSS WEST AND CENTRAL WYOMING WILL BE MOSTLY  
ISOLATED AND CONFINED TO THE HIGHER TERRAIN.  
 
POST-ECLIPSE (TUESDAY THROUGH THURSDAY)...UPPER RIDGE IS EXPECTED TO  
AMPLIFY OVER THE ROCKIES ON TUESDAY AND SLOWLY SHIFT EASTWARD  
INTO THE HIGH PLAINS BY THURSDAY. AN UPPER LOW IS EXPECTED TO  
SHEAR FROM SOUTHERN CALIFORNIA INTO THE GREAT BASIN WEDNESDAY AND  
THURSDAY, AND BRING INCREASING CHANCES OF SHOWERS AND  
THUNDERSTORMS MAINLY TO WESTERN PORTIONS OF WYOMING. TUESDAY AND  
WEDNESDAY ARE EXPECTED TO BE THE WARMEST DAYS OF THIS PERIOD WITH  
MOST HIGHS IN THE 80S TO LOWER 90S ACROSS THE LOWER ELEVATIONS.  
 

 
   
AVIATION
 
12Z ISSUANCE  
 
VFR CONDITIONS WILL OCCUR AT THE TERMINAL SITES THROUGH THE PERIOD.  
ISOLATED SHOWERS AND THUNDERSTORMS WILL OCCUR AFTER 20Z IN THE  
NORTHERN WY MOUNTAINS UNTIL 03Z. NORTHERN JOHNSON COUNTY MAY ALSO  
SEE ISOLATED SHOWERS OR A STORM FROM 21Z UNTIL 03Z. EXPECT BRIEF  
MOUNTAIN OBSCURATION AT TIMES.  

 
   
FIRE WEATHER
 
 
DRIER CONDITIONS WILL MOVE INTO THE AREA TODAY AS HIGH PRESSURE  
BUILDS ACROSS WYOMING. A WEAK UPPER LEVEL DISTURBANCE WILL  
APPROACH MOVE ACROSS MONTANA THIS AFTERNOON AND MAY BRING ISOLATED  
THUNDERSTORMS MAINLY TO JOHNSON COUNTY. BREEZY CONDITIONS WILL  
DEVELOP ACROSS WESTERN AND SOUTHERN WYOMING THIS AFTERNOON.  
ALTHOUGH CRITICAL FIRE CONDITIONS ARE NOT EXPECTED...NEAR CRITICAL  
CONDITIONS MAY OCCUR IN PORTIONS OF SOUTHWESTERN WYOMING. RELATIVE  
HUMIDITY WILL FALL INTO THE TEENS ACROSS MANY OF THE LOWER  
ELEVATIONS THIS AFTERNOON. MIXING AND SMOKE DISPERSAL WILL RANGE  
FROM FAIR IN SOME OF THE NORTHERN BASINS TO VERY GOOD TO EXCELLENT  
IN PORTIONS OF SOUTHERN WYOMING.  
 

 
   
RIW WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...HATTINGS  
LONG TERM...MEUNIER  
AVIATION...ROSS  
FIRE WEATHER...HATTINGS  
 
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