706 FXUS65 KRIW 310919 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 319 AM MDT THU OCT 31 2013 .SHORT TERM...TODAY THROUGH SATURDAY NIGHT WE WILL START THIS MORNING WHAT IS OCCURRING IN THE WIND RIVER BASIN WHERE THE DREADED FOG MONSTER CONTINUES IN PORTIONS OF THE AREA. IN MANY AREAS VISIBILITY HAS BEEN LIKE THIS. FOR THOSE OF YOU OLD ENOUGH TO REMEMBER...REMEMBER THE OLD CARTOONS WITH SING A LONGS WHERE YOU FOLLOW THE BOUNCING BALL. WELL...IN PORTIONS OF THE WIND RIVER BASIN AND LANDER FOOTHILLS WE HAVE BEEN PLAYING FOLLOW THE BOUNCING VISIBILITY. THE WEATHER SERVICE OFFICE HAS BEEN THE BEST EXAMPLE AS WE HAVE GONE FROM 10 MILE VISIBILITY TO A QUARTER OF A MILE IN AN MATTER OF 20 MINUTES. AS A RESULT...WE WILL EXTEND THE DENSE FOG ADVISORY FOR THE WIND RIVER BASIN UNTIL 7 AM. VISIBILITY AT LANDER HAS IMPROVED SO WE WILL LET THE ADVISORY EXPIRE THERE. ELSEWHERE...IT IS MAINLY QUIET THIS MORNING. THE NEXT WEATHER MAKER IN THE FORM OF A SHORTWAVE AND ASSOCIATED COLD FRONT WILL MOVE ACROSS THE STATE LATE TODAY AND TONIGHT. THE FIRST CONCERN IS FOR WIND...ESPECIALLY ACROSS THE SOUTHWESTERN WIND CORRIDOR FROM ROCK SPRINGS THROUGH CASPER AS WELL AS THE CODY FOOTHILLS WITH THE TIGHTENING PRESSURE GRADIENT. UPPER LEVEL WINDS ARE NOT STRONG ENOUGH TO SUPPORT HIGH WIND HIGHLIGHTS BUT GUSTS TO 40 TO 50 MPH IN FAVORED AREAS WILL DEFINITELY BE POSSIBLE. MEANWHILE...IN NORTHWESTERN WYOMING UPSLOPE FLOW AND SOME JET DYNAMICS WILL CAUSE SOME SNOW TO BREAK OUT THIS AFTERNOON AND EVENING. THERE COULD BE A DECENT PERIOD OF SNOW BUT THE STORM IS A QUICK MOVER SO AMOUNTS SHOULD STAY BELOW ADVISORY LEVEL. HOWEVER...A FEW INCHES OF SNOW ARE POSSIBLE IN THE HIGHER ELEVATIONS. ACROSS MOST OF THE BASINS...ANY PRECIPITATION SHOULD BE LIMITED TO SPRINKLES OR FLURRIES WITH STRONG DOWNSLOPING FLOW. RIDGING WILL THEN BUILD ACROSS THE COWBOY STATE ON FRIDAY WITH RISING HEIGHTS HELPING TO SHUT DOWN ANY LINGERING SNOW SHOWER ACTIVITY IN THE MOUNTAINS BY FRIDAY AFTERNOON. FRIDAY NIGHT LOOKS TO BE A DRY AND MAINLY CLEAR NIGHT FOR MOST LOCATIONS. THE WARMEST DAY OF THE PERIOD LOOKS TO BE SATURDAY AS SOUTHWEST FLOW DEVELOPS AHEAD OF THE NEXT SYSTEM THAT WILL BE MOVING THROUGH IDAHO ON SATURDAY. TEMPERATURES MAY BE ABOVE NORMAL FOR THE FIRST TIME SINCE LAST SUNDAY. WITH THE APPROACHING SYSTEM A GUSTY BREEZE WILL ONCE AGAIN DEVELOP ACROSS THE SOUTHWESTERN WIND CORRIDOR AS WELL. THE NAM AND GFS ARE IN FAIRLY GOOD AGREEMENT IN BRINGING PRECIPITATION INTO NORTHWESTERN WYOMING ON SATURDAY NIGHT SO WE BUMPED UP POPS A BIT IN THAT AREA. .LONG TERM...SUNDAY THROUGH THURSDAY A TROUGH EARLY NEXT WEEK WILL BRING COLD AND SNOWY CONDITIONS BACK TO WESTERN AND CENTRAL WYOMING. BY 12Z SUNDAY...A COLD FRONT ASSOCIATED WITH THIS TROUGH SHOULD BE DRAPED ACROSS THE EXTREME WEST AND NORTH...WITH SNOW PROBABLY ONGOING ACROSS NORTHWEST WYOMING. THE FRONT WILL SHIFT EAST AND SOUTH SUNDAY...AND BE THROUGH THE ENTIRE FORECAST AREA BY SUNDAY EVENING. SNOW IS EXPECTED SHIFT EAST OF THE DIVIDE SUNDAY AFTERNOON AND EVENING...WITH MEDIUM RANGE MODELS TRENDING TOWARDS SOME UPSLOPE CONDITIONS DEVELOPING EAST OF THE DIVIDE SUNDAY NIGHT AND LASTING INTO MONDAY. HAVE INCREASED POPS SUNDAY AND MONDAY...WITH AN EMPHASIS ACROSS THE WEST SUNDAY...SHIFTING EAST SUNDAY NIGHT/MONDAY. SOME AREAS COULD SEE ADVISORY AMOUNTS OF SNOWFALL IN THE SUNDAY AND MONDAY TIME FRAME...WITH A FOCUS RIGHT NOW ACROSS FAVORED UPSLOPE LOCATIONS EAST OF THE DIVIDE SUNDAY NIGHT/MONDAY. SOME SNOW WILL LIKELY CONTINUE INTO MONDAY NIGHT AND POSSIBLY INTO TUESDAY AS A SIGNIFICANT SHORTWAVE SWINGS THROUGH THE BASE OF THE TROUGH OVER THE CENTRAL ROCKIES. THE MAIN TROUGH CONTINUES TO SHIFT AWAY FROM THE AREA THURSDAY WITH THE GLOBAL MODELS SHOWING A DRIER NORTHWEST FLOW OR POSSIBLY A TRANSITORY RIDGE AFFECTING THE REGION...BEFORE YET ANOTHER TROUGH POSSIBLY AFFECTS THE REGION NEXT FRIDAY INTO NEXT WEEKEND. TEMPERATURES WILL MAINLY BE BELOW AVERAGE THROUGH THE EXTENDED...WITH MUCH BELOW AVERAGE TEMPERATURES MONDAY AND TUESDAY WHEN HIGHS WILL BE SOME 15 TO 20 DEGREES BELOW AVERAGE. && .AVIATION.../12Z ISSUANCE/ AN AREA OF FOG VCNTY KRIW TO 30SM NW KCPR WILL OBSCURE TERRAIN THROUGH 12Z WITH GRADUAL EROSION OF THE FOG BANK FROM THE WEST...SHOULD BE MOSTLY DISSIPATED BY 15Z. DOWNSLOPE WINDS AT 20-30KTS ALONG THE EAST SLOPES OF THE DIVIDE WILL RESULT IN AREAS OF LLWS VCNTY KCOD-KDUB THROUGH 06Z FRIDAY. MID AND CLOUDS ASSOCIATED WITH A PASSING JET STREAM WILL PUSH EAST OF THE DIVIDE AROUND 14Z. THIS WILL BE FOLLOWED BY AN UPPER LEVEL DISTURBANCE PUSHING EAST ACROSS THE DIVIDE BETWEEN 00Z-06Z FRIDAY. DOWNSLOPE WINDS WILL HINDER MOST PRECIPITATION FORMATION ACROSS THE LOWER ELEVATIONS WITH SNOW SHOWERS OBSCURING MTS ALONG THE DIVIDE AND BIGHORN MTS. DRYING AND AREAS OF GUSTY W-NW WINDS WILL FOLLOW 06Z-12Z FRIDAY. && .FIRE WEATHER... GUSTY WINDS WILL BLOW ACROSS THE SOUTHWESTERN WIND CORRIDOR FROM THE RED DESERT THROUGH NATRONA COUNTY THROUGH TODAY. AN APPROACHING TROUGH AND ASSOCIATED COLD FRONT WILL BRING SOME SNOW SHOWERS MAINLY TO AREAS EAST OF THE DIVIDE AND THE HIGHER ELEVATIONS. WINDS WILL DECREASE TONIGHT AFTER THE PASSAGE OF THE FRONT. RIDGING BUILDING ACROSS WYOMING WILL BRING DRIER WEATHER FROM FRIDAY AFTERNOON INTO SATURDAY. && .RIW WATCHES/WARNINGS/ADVISORIES... DENSE FOG ADVISORY UNTIL 7 AM MDT THIS MORNING WYZ017. && $$ SHORT TERM...HATTINGS LONG TERM...WM AVIATION...AEM FIRE WEATHER...HATTINGS