521 FXUS65 KRIW 121947 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 147 PM MDT WED SEP 12 2012 .SHORT TERM...TONIGHT THROUGH SATURDAY VERY DRY AIRMASS BEGINNING TO DEVELOP OVER THE AREA TODAY AND THIS SHOULD CONTINUE TO EXPAND IN COVERAGE AND INTENSITY THROUGH FRIDAY. THE VERY DRY AIRMASS AND RELATIVELY COOL AIRMASS OVER CENTRAL WYOMING TODAY SHOULD ALLOW FOR SOME COLD OVERNIGHT LOWS AND THE FIRST FREEZE FOR MANY LOCATIONS. FREEZE WARNINGS WILL BE ISSUED FOR THE BIGHORN BASIN...HOT SPRINGS COUNTY...THE WIND RIVER BASIN AND LANDER FOOTHILLS AND SOUTH TO SWEETWATER COUNTY. JOHNSON AND NATRONA COUNTY WILL ALSO SEE FREEZING TEMPERATURES BUT THEY WILL BE CONFINED TO MAINLY LOW LYING AREAS. THE FREEZE WARNING AREAS WILL SEE WIDESPREAD FREEZING TEMPERATURES WITH ONLY THE ELEVATED AREAS ESCAPING. OTHERWISE...IT WILL BE DRY THROUGH THE SHORT TERM WITH WARMING TEMPERATURES INTO FRIDAY BEFORE LEVELING OFF. THERE IS A WEAK DISTURBANCE MOVING IN FROM THE WEST ON SATURDAY WITH AN ASSOCIATED THERMAL TROUGH BUT THE ATMOSPHERE IS FORECAST TO BE SO DRY...PRECIPITABLE WATER AROUND .25 INCHES...THAT IT IS UNLIKELY WE WILL SEE MORE THAN SOME PASSING CLOUDS AND MAYBE A FEW SMALLER CUMULUS. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY A WEAK SHORT WAVE WILL CONTINUE TO WORK ACROSS NORTHWESTERN PORTIONS OF THE STATE. THERE IS VERY LITTLE MOISTURE FOR THE SYSTEM TO WORK WITH SO WE ONLY KEPT VERY ISOLATED POPS ACROSS THE HIGHER ELEVATIONS NEAR YELLOWSTONE PARK. A COLD FRONT THEN DROPS SOUTHWARD ACROSS AREAS EAST OF THE DIVIDE ON SUNDAY. MODELS HAVE BACKED OFF ON THE AMOUNT OF PRECIPITATION SO WE TRIMMED THE COVERAGE A BIT FOR SUNDAY AND SUNDAY NIGHT. THE BEST COVERAGE WILL ONCE AGAIN BE IN THE MOUNTAINS WITH ADDED OROGRAPHIC LIFT. TEMPERATURES LOOK TO BE TRICKY AS A LOT DEPENDS ON THE TIMING OF THE FRONT SO FOR NOW WE LEFT CONTINUITY RIDE FOR THE MOST PART. MONDAY LOOKS TO BE A COOLER DAY BEHIND THE FRONT. HIGHS LOOK TO BE MAINLY IN THE 60S IN THE BASINS AND THE 50S IN THE MOUNTAINS EAST OF THE DIVIDE. THE WARMEST TEMPERATURES LOOK TO BE IN THE WESTERN VALLEYS WHERE JACKSON MAY GET NEAR 70. AS FOR PRECIPITATION...WE LEFT SLIGHT POPS ACROSS MAINLY NATRONA COUNTY WITH THE COLD FRONT POSSIBLY STALLING NEAR THAT AREA. HOWEVER...THIS IS LOOKING LIKE A MORE REMOTE POSSIBILITY AT THIS TIME AND FUTURE SHIFTS MAY WANT TO CONSIDER REMOVING THEM. MODELS THEN SHOW A GENERAL WEST TO NORTHWEST FLOW PATTERN WITH TEMPERATURES RUNNING CLOSE TO SLIGHTLY ABOVE NORMAL AND MAINLY DRY WEATHER. THINGS LOOKED POTENTIALLY INTERESTING FOR NEXT THURSDAY A COUPLE OF DAYS AGO WITH A POTENT SYSTEM DROPPING INTO WYOMING. HOWEVER...MODELS MORE RECENT RUNS OF THE MODELS SHOW THE ENERGY DROPPING INTO THE NORTHERN PLAINS INSTEAD. NEVERTHELESS...SOMETHING TO WATCH IN FUTURE DAYS. AVIATION.../00Z ISSUANCE/ EXPECT VFR CONDITIONS THROUGH 00Z THURSDAY. LOCALLY BREEZY CONDITIONS WILL DIE OFF SHORTLY AFTER SUNSET WITH MAINLY LIGHT WINDS FOR ALL TAF SITES AFTER AROUND 6Z. WITH RIDGING OVERHEAD WINDS WILL BE BELOW 10 KNOTS FOR ALL TAF SITES THURSDAY. AREAS OF SMOKE WILL OCCUR DUE TO WILDFIRES WITH LOCAL MVFR CONDITIONS DUE TO LOW VISIBILITY NEAR AND DOWNWIND OF THE FIRES. FIRE WEATHER... VERY DRY AIRMASS WILL SETTLE IN OVER THE STATE THE NEXT SEVERAL DAYS WITH WARMING TEMPERATURES. AFTER SOME NORTH TO NORTHEAST WINDS OF 10 TO 15 MPH TONIGHT...WINDS WILL GENERALLY BE LIGHT AND DIURNALLY DRIVEN ON THURSDAY. FRIDAY WILL BE VERY DRY WITH SINGLE DIGIT TO LOWER TEEN RH'S WITH TEMPERATURES IN THE 80S EAST OF THE DIVIDE AND 70S TO NEAR 80 WEST. SOME INCREASE IN WEST TO SOUTHWEST WINDS WILL OCCUR FRIDAY BUT MOST AREAS WILL NOT SEE MORE THAN 10 TO 15 MPH SUSTAINED WINDS WITH GUSTS 20 TO 25 MPH. THE CENTRAL AND WESTERN BASINS WILL LIKELY CONTINUE WITH LIGHT WINDS UNTIL EVENING WHEN SOME GUSTY WEST TO NORTHWEST WIND MAY DEVELOP. && .RIW WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING FROM 3 AM TO 9 AM MDT THURSDAY WYZ004>006-017-018-028>030. && $$ SHORT TERM...SKRBAC LONG TERM...HATTINGS AVIATION...HATTINGS FIRE WEATHER...SKRBAC