490 FXUS65 KRIW 120505 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1105 PM MDT FRI OCT 11 2013 .SHORT TERM...TONIGHT THROUGH SATURDAY WV IMAGERY SHOWING TWO MAIN FEATURES OF INTEREST FOR OUR IMMEDIATE FUTURE...ONE THE MONSTER UPR LOW CENTERED IN SCNTRL SD THIS MORNING...AND RAPIDLY ACCELERATING TO THE NNE...AND OCCLUDING. THE OTHER IS...BY COMPARISON...A MUCH MORE SUBTLE SW FEATURE THAT DOVE OUT OF THE WRN PROVINCES OF CA AND IS LOCATED IN WRN MT. ANOTHER SW DISTURBANCE FURTHER UPSTREAM...THAT WILL AFFECT THE AREA SUN/MON...IS LURKING OFFSHORE OF WCNTRL BC...BUT WE WILL TALK MORE ABOUT THAT ONE TOMORROW. VIS PRESENTS A VIEW OF A BUNCH OF MOUNTAIN/VALLEY CLOUDS HANGING IN THIS MORNING...WITH SOME MOUNTAIN WAVE CLOUDS DEVELOPING...OUTLINING THE RANGES PERFECTLY. IN THE MEANTIME...THE CNTRL/NRN PLAINS CYCLONE HAS SPUN UP AND SPED THROUGH MUCH QUICKER THAN WE WERE GUESSING...SO THAT PRECIP AND EVEN WINDS WILL WIND DOWN SOONER THAN EXPECTED. SO CLEARING CONDITIONS STARTING AND CONTINUING EVERYWHERE EXCEPT FOR PERHAPS OUR NE FA WHERE THEY WILL BE UNDER THE LIFTING INFLUENCE OF THE SMALL MT SW BY MID DAY AND MAY NOT EVER CLEAR OUT. ADDITIONALLY...THERE ARE A FEW LIGHT SHOWERS ASSOCIATED WITH THE MT SW DISTURBANCE CURRENTLY IN THE CNTRL PORTION OF MT THAT MAY AFFECT US BY LATE AFTERNOON ALONG AND JUST AHEAD OF THE SW TROF AXIS FOR A FEW HOURS. THIS FEATURE TOO HOWEVER IS MOVING QUITE FAST AND WILL HAVE LITTLE OVERALL EFFECT WITH LITTLE MOISTURE TO WORK WITH. IT WILL MOST LIKELY TAKE MOUNTAINS TO WRING MUCH OF ANYTHING OUT OF THIS...WITH NOTHING BUT A SPRINKLE OR TWO AT LOWER ELEVATIONS. AS THE SW TROF AXIS MOVES THROUGH...BIG HORNS WILL HAVE THE BEST CHANCE FOR SNOW SHOWERS...FOLLOWED BY THE SRN ABSAROKAS...PERHAPS DOWNSTREAM INTO THE OWL CREEK RANGE FOR A FEW HOURS...AND LASTLY MOSTLY FLURRIES IN THE WIND RIVERS. OTHERWISE...NW WINDS IN NRN JOHNSON COUNTY WILL CONTINUE ON THE HIGH SIDE WITH GUSTS TO 45 MPH THROUGH THE MORNING...BUT THEN BEGIN TO DROP THIS AFTERNOON. TONIGHT AND SATURDAY...LOW TEMPS NEAR OR BELOW THE FREEZING MARK EVERYWHERE...WITH MOUNTAIN AREAS FALLING INTO THE TEENS AND 20S. TOMORROW...HIGHS WARM UP OVER TODAY...REACHING TO NEAR 50 OR JUST ABOVE 50 AT LOW ELEVATIONS...30S AND 40S IN THE MOUNTAINS. THERE COULD BE SOME LOW CLOUDS AND/OR SOME LIGHT FOG CONDITIONS UP IN THE YELLOWSTONE AREA BY SUN-UP...BUT WILL BE SHORT-LIVED IF IT HAPPENS. THE BIG HORNS WILL LIKELY HAVE SOME LINGERING LOW CLOUDS THROUGH THE MORNING HRS TOO. THROUGH THE DAYTIME PERIOD SAT...BRIEF SW RIDGING TAKING PLACE WITH A NICE...BUT COOL...DAY WITH DIFFUSE SFC PATTERN AND LITTLE WIND AS NEXT SYSTEM BEGINS TO GATHER SHAPE FOR THE LATTER HALF OF THE WEEKEND OUT IN THE WRN CONUS. ONLY FLY IN OINTMENT...IF YOU CAN CALL IT THAT...WILL BE AN INCREASE IN MOSTLY HIGH TO MID LVL CLOUDINESS WEST OF THE DIVED THROUGH THE AFTERNOON. THERE COULD BE AN SLIGHT POSSIBLITY THAT OUR WRN MOUNTAINS COULD GO CONVECTIVE WITH A FEW RAIN/SNOW SHOWERS POSSIBLE BY LATE AFTERNOON. .LONG TERM...SATURDAY NIGHT THROUGH FRIDAY A LINE OF SHOWERS FROM NORTHERN UTAH...EASTERN IDAHO AND WESTERN MONTANA WILL MOVE INTO THE WEST SATURDAY NIGHT AS SOUTHWEST FLOW DEVELOPS AHEAD OF THE NEXT PACIFIC TROUGH. SNOW SHOWERS WILL INCREASE ACROSS THE WEST BY EARLY SUNDAY MORNING AND SPREAD EAST ACROSS THE NORTH. SNOW SHOWERS...WITH SOME RAIN SNOW MIX IN THE LOWER ELEVATIONS WILL INCREASE AND SPREAD ACROSS THE AREA SUNDAY AFTERNOON AND EVENING. PRECIPITATION SHOULD CHANGE TO ALL SNOW BY LATE EVENING AND CONTINUE THROUGH THE NIGHT. MONDAY WILL BE COLDER WITH AREAS OF SNOW MOST NUMEROUS IN THE NORTH AND EAST AS NORTH NORTHEAST FLOW SPREADS OVER THE AREA AS THE UPPER TROUGH PASSES TO THE EAST. LIGHT SNOW WILL LINGER THROUGH THE NIGHT IN THE NORTH AND EAST WHILE DECREASING THROUGH MONDAY NIGHT. WIDELY SCATTERED SNOW SHOWERS WILL LINGER IN THE EAST TUESDAY MORNING THEN CLEARING WILL OCCUR FROM WEST TO EAST. TUESDAY NIGHT WILL BE COLD WITH AT LEAST PARTIAL CLEARING. SOME FOG MAY DEVELOP IN THE BASINS AND VALLEYS DEPENDING ON THE SNOWFALL THAT OCCURS WITH THIS SYSTEM. THE MODELS SHOW ENOUGH DISAGREEMENT WITH THE STRENGTH AND TRACK OF THIS SYSTEM TO INCREASE THE UNCERTAINTY IN THE FORECAST. WEDNESDAY WILL BE MOSTLY CLEAR AND COOL WITH COLD HIGH PRESSURE SETTLING IN OVER THE AREA IN THE MORNING. CLOUDS WILL INCREASE FROM THE NORTH WITH ISOLATED SNOW SHOWERS MAINLY IN THE NORTHERN MOUNTAINS. SOME MOUNTAIN SHOWERS MAY OCCUR ON THURSDAY WITH PARTIAL CLEARING ON FRIDAY. WITH NORTHERLY FLOW ALOFT THROUGH THE EXTENDED TEMPERATURES WILL REMAIN UNSEASONABLY COOL. THE MODELS HAVE SUCH A WIDE SPREAD OF SOLUTIONS BY THURSDAY THAT LITTLE CONFIDENCE IN THE FORECAST IS WARRANTED. && .AVIATION.../06Z ISSUANCE/ MAINLY SKC CONDITIONS WILL OCCUR FOR THE NEXT FEW HOURS...FOLLOWED BY A QUICK INCREASE IN HIGH LEVEL CLOUDS...FOLLOWED BY MID LEVEL CLOUDS SATURDAY. A FEW SHOWERS COULD OCCUR...MAINLY ACROSS THE NORTHWEST MOUNTAINS THIS AFTERNOON AND EVENING. BRIEF MVFR/IFR CONDITIONS COULD OCCUR WITH THIS ACTIVITY...BUT THEY SHOULD NOT IMPACT ANY TAF SITE. THUS...VFR CONDITIONS IS EXPECTED THROUGH THE FORECAST PERIOD WITH MAINLY LIGHT WINDS AT AREA TAF SITES. && .FIRE WEATHER... TODAY...NO FIRE WEATHER CONCERNS THROUGH THE WEEKEND...AS TEMPERATURES...RH VALUES...AND WINDS BEHAVE FOR THE MOST PART FOR ALL DISPATCH ZONES. ONE EXCEPTION FOR WINDS THIS AFTERNOON WILL BE EAST OF THE DIVIDE...PARTICULARLY IN JOHNSON COUNTY WHERE NW WINDS COULD GUST AS HIGH AS 30 TO 40 MPH INTO THE EARLY PORTION OF THE EVENING. THERE MAY BE A COUPLE OF HIGH MOUNTAIN SNOW SHOWERS DEVELOP LATE SATURDAY AFTERNOON IN THE WESTERN DISPATCH ZONES. OTHERWISE...WINDS WILL TURN MORE OUT OF THE SOUTH TO SOUTHWEST SATURDAY...WITH GUSTY CONDITIONS TO 20 MPH POSSIBLE ACROSS THE SOUTHEASTERN DISPATCH ZONES...WHILE CLOUDS BEGIN TO INCREASE FROM THE WEST AHEAD OF THE NEXT APPROACHING WEATHER SYSTEM WHICH WILL GET HERE OVERNIGHT SATURDAY AND THROUGH SUNDAY...WITH MORE SNOW EXPECTED. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...BRAUN LONG TERM...C.BAKER AVIATION...WM FIRE WEATHER...BRAUN