RSS FeedsIssued by NWS Riverton, WY
000 FXUS65 KRIW 242126 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 226 PM MST TUE NOV 24 2009 .SHORT TERM...TONIGHT THROUGH FRIDAY COLD FRONT IS PUSHING SOUTH THROUGH NRN MT ATTM AND SHOULD PUSH INTO NRN JOHNSON COUNTY BETWEEN 01Z AND 02Z. SHOULD SEE SOME LIGHT SNOW AND GUSTY WINDS DEVELOP BEHIND IT AS MODERATE COMBINATION OF SURFACE FRONT AND MID LEVEL QG FRONTOGENESIS COMBINE TO PRODUCE MODERATE OMEGA AND A PERIOD OF LIGHT SNOW. COULD SEE A QUICK 1 TO 3 INCHES IN THE BIG HORNS AND UP TO AN INCH ACROSS THE PLAINS. CHANCES OF SNOW DIMINISH AS YOU HEAD FURTHER SOUTH INTO NATRONA COUNTY LATER TONIGHT BUT LOW CLOUDS ARE MORE CERTAIN. INVERSIONS HOLDING STRONG ACROSS THE WEST WITH TEMPERATURES STRUGGLING INTO THE MID AND UPPER 20S ACROSS THE STAR AND JACKSON VALLEYS AND LOWER SPOTS OF YNP. RIDGE BUILDS OVER THE AREA WEDNESDAY INTO THANKSGIVING DAY WITH STEEPENING LOW LEVEL INVERSIONS AND WARMING MID LEVEL TEMPS. LOW CLOUDS WILL LIKELY STICK AROUND IN THE WRN VALLEYS...ESPECIALLY LATE AT NIGHT AND IN THE MORNING. CHILLY TEMPS WILL ALSO HOLD ON IN JACKSON AND STAR VALLEYS AND LOWER ELEVATIONS OF YNP WITH MUCH MILDER READINGS IN THE FOOTHILLS AND MTNS. HIGHS WILL BE 10 TO 20 DEGREES WARMER IN THE FOOTHILLS MOUNTAINS UP TO AT LEAST 9K FEET THAN THEY WILL BE ON THE VALLEY FLOOR. SIMILAR CONDITIONS ARE EXPECTED IN THE WIND RIVER BASIN. THE WIND CORRIDOR WILL BE WINDY TO VERY WINDY MUCH OF THIS PERIOD AFTER THEY KICK BACK IN AGAIN LATER WEDNESDAY AFT AND EVENING. WINDS LOOK STRONGER WITH TIME THURSDAY INTO FRIDAY. SERPED IN QUITE A BIT OF WIND POINTS AND HOPEFULLY THOSE WILL BE GOOD STARTING POINTS TO WORK FROM THE NEXT FEW SHIFTS. COLD FRONT APPROACHES LATE FRIDAY AFTERNOON OR JUST BEYOND IN THE FAR WEST WITH POSSIBLE INVERSION EROSION IF GRADIENT IS STRONG ENOUGH. FRIDAY COULD BE THE WARMEST DAY...ESPECIALLY FOR THE BIG HORN AND WIND RIVER BASINS IF THE WINDS MIX DOWN. ADJUSTED SOME VALLEYS AND BASINS DOWNWARD AND A FEW WINDY AREAS AND JOHNSON COUNTY UPWARD THE NEXT COUPLE DAYS. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY A TROUGH WILL PUSH ACROSS THE WEST INTO THE ROCKIES FRIDAY/FRIDAY NIGHT...REMAINING OVER THE AREA THROUGH THE HOLIDAY WEEKEND. MEDIUM RANGE MODELS ARE SHOWING THE BULK OF THE ENERGY WITH THE INITIAL PUSH OF THE LONGWAVE TROUGH...REMAINING WEST/NORTHWEST OF THE AREA. MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT IN SOME DECENT ENERGY ON THE BACKSIDE OF THIS TROUGH DIGGING FRIDAY NIGHT THROUGH SATURDAY NIGHT INTO THE FOUR CORNERS REGION/DESERT SOUTHWEST. THE 00Z ECMWF DIGS IT FARTHER WEST/SOUTHWEST THAN THE GFS. BY SATURDAY NIGHT...THE LONGWAVE TROUGH IS PROJECTED BY THE MEDIUM RANGE MODELS TO BE EFFECTIVELY SPLIT...WITH A CIRCULATION OVER THE SOUTHERN ROCKIES...AND ANOTHER ONE OVER THE NORTHERN HIGH PLAINS. THIS LONGWAVE TROUGH IS THEN PROJECTED TO SLOWLY EJECT EAST SUNDAY AND MONDAY...WITH THE SOUTHERN PART BECOMING CUT OFF OVER THE SOUTHERN PLAINS. BEST CHANCES FOR SNOW WITH THIS TROUGH SHOULD BE FRIDAY NIGHT AND SATURDAY OVER THE WEST...AS THE ENERGY ON THE BACKSIDE OF THE TROUGH BEGINS TO DIG. DEPENDING UPON THE EXACT TRACK WITH THE DIGGING ENERGY...IT COULD ALLOW FOR SOME UPSLOPE CONDITIONS TO DEVELOP EAST OF THE DIVIDE SATURDAY/SATURDAY NIGHT. CURRENTLY...IT DOES NOT APPEAR ANY SIGNIFICANT SNOWFALL IS EXPECTED WITH THIS SYSTEM...BUT WILL OF COURSE NEED TO BE WATCHED. ALTHOUGH PRECIPITATION REMAINS UNCERTAIN WITH THIS SYSTEM...THE COLD FRONT PUSHING ACROSS THE AREA LATE FRIDAY AND FRIDAY NIGHT IS NOT. DRY CONDITIONS ARE EXPECTED MONDAY...WITH A RIDGE OVER THE AREA. HOWEVER THIS WILL BE SHORTLIVED...AS MEDIUM RANGE MODELS SHOW A TROUGH PUSHING SOUTHEAST OUT OF BRITISH COLUMBIA MONDAY NIGHT/TUESDAY...WITH THE GFS SLOWER THAN THE ECMWF. THE WARMEST TEMPERATURES IN THE EXTENDED WILL BE FRIDAY...AHEAD OF THE COLD FRONT PUSHING ACROSS THE AREA LATE FRIDAY/FRIDAY NIGHT. TEMPERATURES SATURDAY AND SUNDAY SHOULD BE SLIGHTLY BELOW AVERAGE...WITH A WARMING TREND MONDAY AND TUESDAY. WENT WITH THE SLOWER SOLUTION OF THE ECMWF WITH NEXT WEEKS TROUGH...AND THUS WITH WARMER TEMPS THAN MEX MOS. && .AVIATION... UPPER LEVEL LOW PRESSURE WILL MOVE RAPIDLY SOUTHEASTWARD TONIGHT ACROSS EASTERN MONTANA AND THE NORTHERN PLAINS STATES. THIS LOW PRESSURE SYSTEM WILL PUSH A COLD FRONT SOUTHWARD THROUGH EASTERN WYOMING AND SOUTH DAKOTA THIS EVENING THROUGH THE EARLY MORNING HOURS. WINDS ACROSS EASTERN CENTRAL WYOMING WILL SHIFT TO THE WEST NORTHWEST AND NORTHWEST AFTER MIDNIGHT FOR A FEW HOURS BEFORE SUNRISE. A WIND SHIFT TO THE WEST NORTHWEST CAN BE EXPECTED AT KCPR AROUND 07Z. AN AREA OF MID LEVEL CLOUDS WILL CROSS WESTERN AND CENTRAL WYOMING TONIGHT WITH CEILINGS FALLING TO AROUND 10 K FEET IN MOST AREAS...EXCEPT TO BETWEEN 5 K FEET AND 8 K FEET IN THE BIGHORN BASIN...JOHNSON COUNTY AND NATRONA COUNTY. KJAC IN THE WEST WILL HAVE BROKEN CEILINGS AT AROUND 3500 FEET TONIGHT...AS LOWER LEVEL MOISTURE BECOMES TRAPPED BENEATH THE RIDGE ALOFT. LIGHT SNOW ASSOCIATED WITH THE UPPER LOW WILL CAUSE MOUNTAIN OBSCURATIONS IN THE BIGHORNS AND BRIEF MVFR CONDITIONS IN JOHNSON COUNTY TONIGHT. HIGH PRESSURE AT THE SURFACE AND ALOFT WILL MOVE ACROSS WESTERN WYOMING AND INTO CENTRAL WYOMING WEDNESDAY WITH GENERALLY LIGHT WINDS AND VFR CONDITIONS. MAINLY SCATTERED HIGH CLOUDS TO CLEAR CONDITIONS ARE EXPECTED WEDNESDAY. WITH DEEP LOW PRESSURE MOVING FROM THE NORTHERN PLAINS INTO THE UPPER MIDWEST WEDNESDAY...SOUTHWEST WINDS AT KCPR COULD GUST UP TO AROUND 20 KT IN THE AFTERNOON. && .FIRE WEATHER... A COLD FRONT WILL SLIDE SOUTH THROUGH THE EASTERN PART OF THE DISTRICT WITH GUSTY NORTH WIND...LOW CLOUDS AND SOME LIGHT SNOW IN JOHNSON COUNTY. OTHERWISE...A RIDGE OF HIGH PRESSURE WILL MOVE OVER THE AREA WEDNESDAY INTO THANKSGIVING DAY PRODUCING STEEP VALLEY AND BASIN INVERSIONS AND DRY CONDITIONS. THE MOUNTAINS AND FOOTHILLS WILL BE WARMER THAN MOST OF THESE TRAPPED BASINS AND VALLEYS. STRONG SOUTHWEST WINDS WILL BLOW ACROSS THE WIND CORRIDOR FROM EASTERN SWEETWATER COUNTY TO NATRONA COUNTY AND IN AT TIMES IN THE HIGH COUNTRY THE NEXT SEVERAL DAYS. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...SKRBAC LONG TERM...WM AVIATION...SMITH FIRE WEATHER...SKRBAC
