063 FXUS65 KRIW 071754 AFDRIW AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE RIVERTON WY 1154 AM MDT WED OCT 7 2015 .SHORT TERM...TODAY THROUGH FRIDAY NIGHT FLOW TURNS MORE NORTHWESTERLY TODAY WITH A SHORT WAVE ZIPPING BY THIS EVENING. LATEST GUIDANCE...WELL MOST OF IT...IS MUCH MORE AGGRESSIVE WITH THIS FEATURE WITH DECENT JET SUPPORT AND IMPROVED MOISTURE SUPPLY AS THE PACNW IS OPEN TO THE TROPICS FOR MUCH OF THE DAY...THEN THE RIDGE BUILDING TO THE SOUTH PINCHES OFF THIS STREAM AND SENDS IT RIDING DOWN THE FRONT SIDE OF THE RIDGE ALONG WITH THE SHORT WAVE...DOWN INTO WYOMING. ONCE IT INTERACTS WITH THE NOSE OF THE JET...AND THE MODELS INDICATE SOME FRONTOGENETIC FORCING ALONG THE WY/MT BORDER LATE TONIGHT INTO EARLY THURSDAY MORNING...ALONG WITH COLD POOLING ALOFT INCREASING THE LAPSE RATE...THERE COULD BE A BETTER PRECIPITATION SHIELD ALONG WITH THIS SYSTEM THAN PREVIOUSLY ADVERTISED. SO...THE AREA OF ISOLATED SHOWERS WAS EXPANDED TO INCLUDE MUCH OF THE BIGHORN BASIN...THE I25 CORRIDOR INCLUDING CASPER...AND PORTIONS OF THE WIND RIVERS AND WIND RIVER BASIN. POPS ARE STILL LOW AS THE VERY RECENT CHANGE IN TUNE FROM THE MODELS LEAVES ME SUSPICIOUS...BUT THE INCREASED QPF IN THE GFS AND THE EUROPEAN IS AT LEAST BACKED UP BY OTHER ELEMENTS OF THE MODELS...LIKE DECENT QG FORCING WITH THE WAVE AND ASSISTANCE FROM THE JET...FRONTOGENETIC FORCING AND A COLDER POOL ALOFT. ALSO THE MOISTURE SOURCE CAN BE VERIFIED ON SATELLITE AT THE MOMENT SO THEY SEEM TO BE INITIALIZING WELL. THE GFS AND THE EUROPEAN ARE ALSO IN DECENT AGREEMENT WITH ONE ANOTHER THIS RUN ON THE TIMING AND STRENGTH OF KEY FEATURES...SO IT IS HARD TO IGNORE...EVEN IF THE NAM AND THE SREF ARE STILL NOT TOTALLY ON BOARD WITH THE INCREASED IMPACT OF THIS SYSTEM...THEY DO STILL CARRY THE SAME TIMING OF THE FEATURE. THIS COULD BE THE FIRST CHALLENGING NORTHWEST FLOW FORECAST OF THE FALL SEASON...IT WILL BE INTERESTING TO SEE HOW THIS EVOLVES. IT LOOKS LIKE THIS FEATURE WILL NOT CLEAR THE AREA UNTIL THURSDAY LATE AFTERNOON INTO THE EVENING...SO EXPECT SHOWERS TO GRADUALLY CLEAR FROM WEST TO EAST LATE THURSDAY WITH SEASONABLY COOL TEMPERATURES FOR MUCH OF THE AREA. ANOTHER SHORT WAVE MOVES BY IN THE NORTHWEST FLOW ON THURSDAY NIGHT ...WITH A COLD FRONT IN TOW. THIS FEATURE IS LACKING A MOISTURE SOURCE AND DOES NOT HAVE MUCH SUPPORT ALOFT...IT WILL DELIVER A SLIGHT CHANCE OF A SHOWER IN THE NORTHERN MOUNTAINS AND SOME NORTHWESTERLY BREEZES BEHIND THE FRONT...WITH A FEW GUSTS AROUND 35 MPH POSSIBLE NEAR BUFFALO AND ALONG THE NORTHERN BIGHORN BASIN. OTHERWISE...IT WILL KEEP A FEW CLOUDS AROUND AND WILL BE OUT OF THE AREA BY FRIDAY NIGHT. .LONG TERM...SATURDAY THROUGH WEDNESDAY ONCE AGAIN...THE LONG RANGE FORECAST LOOKS LARGELY DRY INTO THE FIRST PART OF NEXT WEEK. HOWEVER...THERE ARE A FEW THINGS TO TALK ABOUT. THE FIRST IS THE WARM TEMPERATURES. HIGH TEMPERATURES WILL BE WELL ABOVE NORMAL WITH THE RIDGE OF HIGH PRESSURE IN CONTROL OF THE WEATHER ALONG WITH A WARMING WEST TO SOUTHWEST WIND. SOME OF THE WARMER SPOTS WILL LIKELY TOP THE 80 DEGREE MARK BOTH SATURDAY AND SUNDAY. HOWEVER..THE MORE IMPORTANT ASPECT WILL BE THE WIND. A COUPLE OF SHORTWAVES WILL PASS BY TO THE NORTH. THESE ARE LIMITED WITH MOISTURE AND MOST OF THE LIFT WILL STAY TO THE NORTH. AS A RESULT...OTHER THAN THE FAR NORTHERN MOUNTAINS WE SHOULD STAY DRY. HOWEVER...THEY WILL BE CLOSE ENOUGH TO TIGHTEN THE PRESSURE GRADIENT. THE WIND WILL INCREASE SATURDAY AND BECOME GUSTY IN THE USUAL AREAS. HOWEVER...SUNDAY AT THIS POINT COULD BECOME DOWNRIGHT WINDY. BOTH THE GFS AND EUROPEAN MODELS SHOW 700 MILLIBAR WINDS OF 40 TO CLOSE TO 50 KNOTS. IN ADDITION...WE COULD HAVE SOME JET SUPPORT TO MIX THE STRONGER WINDS TO THE SURFACE AND APPROACHING COLD FRONT. THIS...COMBINED WITH THE WARM TEMPERATURES AND LOW HUMIDITY COULD INCREASE FIRE DANGER EACH AFTERNOON...BUT ESPECIALLY SO ON SUNDAY. THE AFOREMENTIONED COLD FRONT WILL PASS THROUGH SUNDAY BUT AGAIN LARGELY WITH ONLY SOME WIND AND NOT WITH MUCH PRECIPITATION AND ONLY A SMALL DROP IN TEMPERATURES. ANOTHER SHORTWAVE MAY CROSS THE AREA ON TUESDAY BUT AGAIN THE MAIN EFFECT WITH MORE GUSTY BREEZES AND NOT PRECIPITATION AND A BIG DROP IN TEMPERATURES. && .AVIATION.../18Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES VFR CONDITIONS WITH SKC TO SCT MID/HIGH LEVEL CLOUDINESS ARE EXPECTED THROUGH 21Z. WINDS ARE ALSO EXPECTED TO BE MAINLY LIGHT TODAY...WITH CPR BEING BREEZY FROM THE SOUTHWEST...VEERING TO THE WEST BY MIDDAY. MID AND HIGH LEVEL CLOUDS WILL CONTINUE TO INCREASE FROM THE NORTHWEST TO SOUTHEAST THIS AFTERNOON...AHEAD OF A WEAK SYSTEM IN THE NORTHERLY FLOW. THIS SYSTEM WILL PUSH ACROSS THE AREA TONIGHT...WITH ISOLATED TO LOCALLY SCATTERED SHOWERS...MAINLY OVER THE NORTHERN MOUNTAINS...BUT CANNOT RULE OUT SOME ACTIVITY EVEN SPREADING INTO THE LOWER ELEVATIONS ACROSS THE BIG HORN BASIN AND JOHNSON COUNTY. BRIEF MVFR CONDITIONS IN SHOWER ACTIVITY...ALONG WITH NORTHERN MOUNTAIN OBSCURATIONS AT TIMES WILL BE THE MAIN ISSUES...ESPECIALLY AFTER 03Z. THE MAIN EXCEPTION WOULD PROBABLY BE ACROSS MUCH OF JOHNSON COUNTY...AND THE NE BIG HORN BASIN WHERE MVFR CEILINGS COULD DEVELOP AFTER 06Z IN WAKE OF A WEAK COLD FRONT. HOWEVER THESE LOW CEILINGS ARE NOT EXPECTED TO IMPACT ANY TAF TERMINAL AT THE MOMENT. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES FOG/STRATUS WILL BE THE MAIN AVIATION CONCERN EARLY THIS AFTERNOON IN THE JACKSON VALLEY...WITH THE ASSOCIATED MOUNTAIN OBSCURATIONS. HOWEVER...THE CLOUD DECK SHOULD ONLY BE 500 FEET THICK...WITH MAINLY SKC CONDITIONS ABOVE IT. THE LOW STRATUS CLOUD DECK SHOULD DISSIPATE BY 20Z. OUTSIDE OF FOG/STRATUS...CONDITIONS WILL BE MAINLY SKC WITH MAINLY LIGHT WINDS...WITH A TAD STRONG WESTERLY WIND ACROSS SWEETWATER COUNTY. A WEAK SYSTEM WILL PASS ACROSS SOUTHERN MONTANA/NORTHERN WYOMING TONIGHT...BUT ONLY AN INCREASE IN MID/HIGH LEVEL CLOUDINESS IS EXPECTED. THE PRECIPITATION AND ANY ASSOCIATED LOW CLOUDS WITH THIS SYSTEM TONIGHT IS EXPECTED TO REMAIN EAST OF THE DIVIDE. && .FIRE WEATHER... A BETTER SHOT AT A WETTING RAIN ACROSS THE NORTHERN MOUNTAINS LATER TODAY...AND A NON-ZERO SHOT ALONG THE FOOTHILLS IN CASPER AND CODY DISPATCH AS A WEATHER SYSTEM MOVES BY IN THE NORTHWEST FLOW TONIGHT INTO THURSDAY. THERE WILL ALSO BE A COUPLE OF COLD FRONTS PUSHING SOUTH OVER THE NEXT COUPLE OF DAYS...KEEPING RELATIVE HUMIDITIES ON THE MODERATE SIDE AND TEMPERATURES COOL. MUCH DRIER AIR MOVES IN SATURDAY BEHIND THESE SYSTEMS WITH A STRONG WIND EVENT POSSIBLE ON SUNDAY. AT THIS TIME...IT LOOKS LIKE THERE WILL BE SOME HIGHER RELATIVE HUMIDITIES BEHIND THE STRONG WIND BUT THERE COULD BE SOME DOWNSLOPE DRYING THAT COULD PUSH RELATIVE HUMIDITIES INTO THE LOW TEENS ON SUNDAY...WILL CONTINUE TO MONITOR IN CASE A WATCH IS NEEDED...WOULD LIKE TO SEE A LITTLE MORE MODEL AGREEMENT ON TIMING AND STRENGTH OF THE SYSTEM THIS WEEKEND BEFORE HOISTING A WATCH. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...ALLEN LONG TERM...HATTINGS AVIATION...WM/LIPSON FIRE WEATHER...ALLEN