RSS FeedsIssued by NWS Riverton, WY
000 FXUS65 KRIW 202204 AFDRIW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 304 PM MST FRI NOV 20 2009 .SHORT TERM...TONIGHT THROUGH MONDAY FLOW CONTINUES TO BACK TO THE SOUTH OVER WYOMING AS AMPLIFIED TROUGH ALONG PAC COAST APPROACHES. SCT-BKN HIGH CLOUDS IN THE ADVANCE OF THE TROUGH PUSHING ACROSS THE AREA SINCE THIS MORNING AND WILL CONTINUE TO DO SO OVERNIGHT. WEAK BAROCLINIC LEAF LOCATED OVER CENTRAL WA/OR THIS AFTERNOON WITH RA/SN FALLING UNDERNEATH THIS FEATURE. 3-5MB/3HR PRESSURE FALLS WIDESPREAD OVER THE GREAT BASIN AND CENTRAL/NORTHERN ROCKIES THIS AFTERNOON. LEE TROUGH OVER EASTERN WY/CENT MONTANA GETTING THE CENTRAL WIND CORRIDOR GOING. TIGHT S TO SSW GRADIENT OVER THE FAR WEST GETTING THE MOUNTAIN LOCATIONS BLOWING PRETTY GOOD AS WELL. FOR THE OVERNIGHT...GRADIENT TIGHTENS ACROSS THE AREA...WITH WINDS INCREASING OVER THE CENTRAL WIND CORRIDOR AND WESTERN MOUNTAINS. AFTER MIDNIGHT...NAM AND LOCAL WRF SHOWING 50-60KTS OVER THE LEE SLOPES OF THE WINDS AND THE ABSAROKAS. HAVE INCREASED THE WINDS THERE TO REFLECT THIS. COULD SEE SOME LOCAL HIGH WINDS IN THE MOUNTAINS OVER THE SOUTHEAST PORTION OF THE WINDS AND AROUND CHIEF JOSEPH AND OTHER HIGH PEAKS OF THE EASTERN ABSAROKAS. ALSO...WILL LIKELY SEE FALES ROCK AND CAMP CREEK BLOW HIGH WIND...BUT AGAIN THIS WILL BE LOCALIZED. THE EARLIER CONCERNS OF POSSIBLE HIGH WINDS NEAR LANDER ARE NO LONGER ANTICIPATED WITH LACK OF CRITICAL LAYER AND NO DOWNWARD FORCING TO SURFACE THESE WINDS ALOFT. WINDS TAPER AROUND 12Z SATURDAY WITH LIGHT SNOW DEVELOPING IN THE WEST AS THE BAROCLINIC LEAF MOVES INTO THE WEST. THIS FEATURE WILL WEAKEN AS IT MOVES THROUGH AND LIFTS TO THE NORTH. EXPECT LIGHT TO LOCALLY MODERATE SNOW TO FALL OVER THE NORTHWEST MOUNTAINS...WITH MAINLY LIGHT SNOW IN JACKSON HOLE. SNOWFALL OF 2 TO 4 INCHES EXPECTED IN THE MOUNTAINS WITH AN INCH OR SO IN THE VALLEY BEFORE TAPERING QUICKLY SATURDAY EVENING. SHORTWAVE RIDGING BUILDS IN SATURDAY NIGHT BRINGING A BRIEF RESPITE FROM THE SNOW. HOWEVER...A STRONGER WAVE WHICH IS DIGGING IN BEHIND THE INITIAL WAVE SOUTH OF ALASKA WILL MOVE IN SUNDAY MORNING...BRINGING ANOTHER ROUND OF SNOW TO MUCH OF THE WEST. NICE CYCLONICALLY ORIENTED JET WILL MOVE INTO THE WEST DURING THE DAY SUNDAY WILL PROVIDE GOOD LIFT. ALSO HAVE GOOD LOW AND MID LEVEL CONVERGENCE AS WELL AS SOME ISENTROPIC LIFT IN THE MORNING. EXPECT A DECENT PERIOD OF LIGHT TO MODERATE SNOW WITH THIS FEATURE FROM MID TO LATE SUNDAY MORNING THROUGH SUNDAY EVENING. A COLD FRONT MOVES INTO AREAS EAST OF THE DIVIDE SUNDAY NIGHT. COULD SEE SOME DECENT NORTHWEST WINDS OVER THE WIND RIVER AND BIGHORN BASINS AS WELL AS JOHNSON COUNTY AS THE TROUGH DIGS SOUTHEAST ACROSS SE MT INTO THE DAKOTAS. SOME LIGHT SNOW IS POSSIBLE OVER THE BIGHORNS AND JOHNSON COUNTY SUNDAY NIGHT AS WELL. NORTHWEST FLOW CONTINUES MONDAY OVER THE AREA...WITH SOME LIGHT SNOW SHOWERS LINGERING OVER THE MOUNTAINS AND THEIR SOUTHEAST. PRETTY COLD TEMPERATURES WILL MOVE IN BEHIND EACH TROUGH. H7 TEMPS DOWN TO -17C OVER THE WEST WITH -14C EAST OF THE DIVIDE. WILL BE SEEING OVERNIGHT LOWS IN THE SINGLE DIGITS AND TEENS WITH SOME LOWER 20S EAST. .LONG TERM...MONDAY NIGHT THROUGH FRIDAY A GRADUAL WARMING TREND IS EXPECTED TUESDAY ONWARD WITH A SLIGHT CHANCE FOR RAIN OR SNOW ACROSS THE NORTH AND EAST TUESDAY NIGHT AND WEDNESDAY. DRY AND UNSEASONABLY MILD CONDITIONS EXPECTED THANKSGIVING DAY. BLACK FRIDAY LOOKS MILD AND BREEZY OVER MOST OF THE AREA WITH A CHANCE OF PRECIPITATION RETURNING TO THE WEST AHEAD OF A COLD FRONT LIKELY TO MOVE ACROSS THE AREA FRIDAY NIGHT AND SATURDAY. MEDIUM-RANGE GLOBAL MODELS CONTINUE TO SHOW SPREAD WITH TROUGH EXITING INTO THE HIGH PLAINS MONDAY MORNING...THE GFS REMAINS THE MOST PROGRESSIVE...THE GEM AND UKMET THE SLOWEST AND DEEPEST...AND THE ECMWF THE PREFERRED COMPROMISE BETWEEN THE THREE. ALL FOUR MODELS SEEMED TO HAVE SETTLED ON THESE INDIVIDUAL SOLUTIONS OVER THE LAST FEW RUNS WITH LESS SPREAD THIS MORNING BETWEEN THE FOUR. FORECAST WEIGHTED TOWARD ECMWF THROUGH THE EXTENDED PERIOD. ALL MODELS QUICKLY DRY OUT AIRMASS MONDAY BEHIND UPPER TROUGH...THE ECMWF AND GEM LEAVING LIGHT QPF ACROSS THE FAR WEST AND SOUTHEAST QUARTER IN COLDER MORE AMPLIFIED FLOW BEHIND TROUGH. SLOWER CLOSED LOW OVER THE PLAINS ALSO HAS IMPLICATIONS FOR CLIPPER SYSTEM DIVING INTO BACK SIDE OF CLOSED LOW. GFS FLATTER FLOW RESULTS IN MORE ISENTROPIC UPGLIDE...PRECIPITATION ACROSS THE NORTH AND WEST TUESDAY AND TUESDAY NIGHT. ECMWF BRINGS BACKDOOR COLD FRONT INTO NORTHEAST HALF OF STATE TUESDAY NIGHT WITH SOME LIGHT QPF WHILE KEEPING WEST DRY. UPPER RIDGE PREVAILS WEDNESDAY AND THANKSGIVING DAY WHERE MODELS TEND TO COME BACK INTO AGREEMENT. ECMWF SOLUTION PREFERRED LATE IN THE PERIOD SHOWING PACIFIC ENERGY SPLITTING INTO INTERMOUNTAIN WEST FRIDAY WITH SLIGHT CHANCES OF PRECIPITATION RETURNING TO THE NORTHWEST MOUNTAINS. BEYOND THIS PERIOD FOR HOLIDAY TRAVELERS...COLDER CONDITIONS WITH A CHANCE OF LIGHT SNOW EXPECTED WYOMING AND THE CENTRAL ROCKIES SATURDAY AS THIS SPLIT TROUGH MOVES ACROSS THE AREA. && .AVIATION... BKN-OVC HIGH CLOUDS WILL CONTINUE TO OVERSPREAD WYOMING THROUGH THIS EVENING. LIGHT TO MODERATE SOUTHWEST WIND WILL DEVELOP OVER MOST AREAS THIS EVENING...EXCEPT IN THE WIND CORRIDOR FROM SOUTHEAST FREMONT INTO NATRONA COUNTY INCLUDING KCPR...WHERE STRONG SOUTHWEST WINDS BETWEEN 16 AND 22KT ARE EXPECTED...WITH GUSTS AROUND 28 KNOTS POSSIBLE. SOUTHWEST WIND WILL REMAIN STRONG IN THIS REGION THROUGH SATURDAY. ELSEWHERE...SOUTHWEST WIND WILL BE ON THE INCREASE TONIGHT ESPECIALLY ALONG AND IN THE LEE OF THE MOUNTAINS. WIDESPREAD LIGHT TO MODERATE SNOW IS EXPECTED TO BEGIN OVER THE FAR WEST AFTER ABOUT 10Z SATURDAY. MOUNTAIN OBSCURATIONS...AREAS OF MVFR... AND LOCAL IFR CONDITIONS ARE EXPECTED TO IMPACT THE KJAC TERMINAL THROUGH THE DAY SATURDAY. && .FIRE WEATHER... THE WEEKEND AHEAD WILL BE UNSETTLED WITH WINDY AND DRY CONDITIONS EAST OF THE DIVIDE. RH`S WILL BE QUITE LOW OVER THE BASINS SATURDAY AND SUNDAY POSSIBLY DIPPING INTO THE TEENS. SNOW CAN BE EXPECTED SATURDAY AND SUNDAY WITH A BRIEF BREAK SATURDAY NIGHT. SNOWFALL OF THE UP TO 5 INCHES IS POSSIBLE IN THE NORTHWEST EACH DAY...AND IN THE SOUTHWEST MOUNTAINS ON SUNDAY. A COLD FRONT WILL MOVE THROUGH SUNDAY NIGHT WITH SOME SNOW SHOWERS POSSIBLE IN THE MOUNTAINS AND EVEN EAST OF THE DIVIDE THROUGH MONDAY. MILD AND DRY CONDITIONS RETURN FOR THE REMAINDER OF THE UPCOMING WEEK. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...TWB LONG TERM...AEM AVIATION...CHURCH FIRE WEATHER...TWB
