Favorable jet stream dynamics coupled with a strong surface cold front to produce high winds in areas lee of the Wind River Mountains and within a favored wind corridor in Sweetwater County.
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The episode as NWS RIW wrote it up.
Favorable jet stream dynamics coupled with a strong surface cold front to produce high winds in areas lee of the Wind River Mountains and within a favored wind corridor in Sweetwater County.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Riverton, WY wrote its last area forecast discussion before the first event at May 28, 2:14 AM MST, 6 hours 1 minute earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 314 AM MDT FRI MAY 28 2010 .SHORT TERM...TODAY THROUGH SUNDAY NIGHT COMPLEX CLOSED UPPER LOWS SPINNING OVER THE WESTERN WESTERN STATES EARLY THIS MORNING. THESE CIRCULATIONS WILL GRADUALLY MORPH INTO ONE CIRCULATION LATER TODAY. NUMERICAL MODEL SOLUTIONS IN GOOD AGREEMENT THROUGH TODAY WITH THE MUCH STRONGER SOUTHERN SHORT-WAVE TROUGH/VORT LOBE OVER CENTRAL CALIFORNIA LIFTING NORTHEASTWARD THROUGH WESTERN WYOMING THIS EVENING. THE ASSOCIATED STRONG SURFACE COLD FRONT WILL MOVE THROUGH AREAS WEST OF THE DIVIDE THIS AFTERNOON WITH WIDESPREAD RAIN AND HIGH MOUNTAIN SNOWFALL EXPECTED THROUGH MID EVENING. MODEL SOLUTIONS DIVERGE TONIGHT AND SATURDAY MORNING...WITH THE GFS FASTER AND MUCH DRIER THAN THE 00Z NAM AND ECMWF SOLUTIONS. LOWERED PRECIP CHANCES SATURDAY AFTERNOON AND EVENING...COMPROMISING BETWEEN THE SLOWER AND WETTER ECMWF AND THE BONE DRY GFS GIVEN THE THIS UNCERTAINTY. MOST GLOBAL MODEL SOLUTIONS LEANING TOWARD A FARTHER NORTH SOLUTION WHICH WOULD LEND SOME CREDENCE TO THE GFS AND THE FASTER WEST TO EAST JET LEVEL FLOW OVER WYOMING. ECMWF HAS BEEN QUITE CONSISTENT...HOWEVER...THE PAST SEVERAL DAYS WITH THE WETTER SOLUTION...BUT TRENDING DRIER AND FARTHER NORTH WITH THE CLOSED H7 AND H5 CIRCULATIONS. FLOOD WATCH STILL A POSSIBILITY FOR JOHNSON COUNTY FOR SATURDAY AND SATURDAY EVENING...BUT SEEMS LESS LIKELY WITH LOCAL QPF AMOUNTS IN THE WETTEST OF SOLUTIONS BELOW THREE QUARTERS OF AN INCH. THE DAY SHIFT CAN TAKE A LOOK AT THE 12Z SOLUTIONS WITH PLENTY OF ONSHORE DATA AVAILABLE AS THE CLOSED LOW AND NORTHWEST JET MOVE INLAND THIS MORNING. LOWERED PRECIPITATION CHANCES FOR SUNDAY AND SUNDAY NIGHT...ESPECIALLY EAST OF THE DIVIDE WITH ONLY A WEAK...SLIGHTLY UNSTABLE...CYCLONIC WESTERLY FLOW REMAINING IN ALL GLOBAL MODEL PROGS OVER CENTRAL WYOMING. .LONG TERM...MEMMORIAL DAY THROUGH FRIDAY MEMORIAL DAY LOOKS MOSTLY DRY WITH A SLIGHT CHANCE OF MOUNTAIN SHOWERS AND STORMS AS WELL ACROSS LOWER ELEVATIONS NORTHERN WY. THIS IS WHERE THE BEST INSTABILITY WILL BE AS WELL AS LOW LEVEL MOISTURE. THE ACTIVITY WILL LINGER INTO THE EVENING HOURS WITH ONLY ISOLATED SHOWERS AFTER MIDNIGHT. A SHORTWAVE MOVES INTO THE WESTERN STATES ON TUE AND INTO WESTERN WY WY TUE NIGHT. THIS WILL LEAD TO A HIGHER CHANCE OF SHOWERS AND STORMS IN THE WEST. EAST OF THE DIVIDE A SLIGHT CHANCE OF SHOWERS AND STORMS IN THE NORTH AND EAST PORTION OF THE CWA IN THE TUE AFTERNOON...THEN POSSIBLY A LITTLE BETTER COVERAGE TUE NIGHT AS THE SYSTEM MOVES ACROSS WY. GFS IS SLOWER THAN THE ECMWF MODEL ON WED IN MOVING THE SHORTWAVE OUT OF THE REGION. THIS WOULD LEAD TO A SLIGHT CHANCE OF STORMS IN THE EAST ZONES WED PM WITH LESS ACTIVITY ELSEWHERE. MADE MINOR CHANGES TO THE FORECAST. THE LONG RANGE MODELS DIFFER THURS AND FRI WITH RESPECT TO TEMPS AND PRECIP CHANCE. THE ECMWF IS COOLER AND WETTER OVER REGION WHILE THE GFS IS DRIER AND WARMER. THE DIFFERENCE LIES IN THE FACT THAT THE GFS HAS MORE RIDGING OVER THE INTERMOUNTAIN REGION WHILE THE ECMWF HAS LOWER 500MB HEIGHTS AND KEEPS MOISTURE STREAMING INTO NW WY. FOR NOW HAVE USED A BLEND IN SOLUTIONS AND WILL KEEP SLIGHT CHANCE OF AFTERNOON AND EVENING SHOWERS AND STORMS THURS AND FRI OVER THE MOUNTAINS AND NORTH. AS FOR TEMPS SEASONAL HIGHS THROUGH TUE THEN COOLER WED. GFS HAS WARMER TEMPS FORECAST THAN THE ECMWF THURS AND FRI. CHOSE TO LEAN TOWARD WARMER GFS NUMBERS BUT NOT AS WARM THE MEX GUIDANCE FIGURES. && .AVIATION... STRONG SOUTH TO SOUTHWEST WINDS ARE EXPECTED TO DEVELOP ONCE AGAIN OVER MUCH OF THE AREA TODAY BETWEEN 15Z AND 20Z TODAY...AND LAST THROUGH EARLY EVENING. THE STRONGEST WINDS ARE EXPECTED TO BE ACROSS SWEETWATER COUNTY...INCLUDING KRKS TERMINAL WHERE SUSTAINED WINDS OF 25 TO 35KT WITH GUSTS TO 45KT WILL BE LIKELY. A MAJOR STORM SYSTEM OVER THE WEST WILL FINALLY BEGIN TO PUSH EAST INTO THE AREA LATE TODAY THROUGH SATURDAY. THE ASSOCIATED COLD FRONT WILL MOVE THROUGH LATE THIS AFTERNOON...AND SHOULD BE THROUGH MUCH OF THE FORECAST AREA BY 06Z SATURDAY. THE BEST CHANCE FOR SHOWERS AND ISOLATED THUNDERSTORMS WILL BE OVER THE NORTHWEST THIS AFTERNOON THROUGH THE NIGHT. AHEAD OF THE FRONT...DRY CONDITIONS ARE EXPECTED...BUT ALONG AND BEHIND THE FRONT...THERE WILL BE A CHANCE FOR SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. VFR CONDITIONS ARE EXPECTED AHEAD OF THE FRONT EXCEPT NEAR CONVECTION. IN WAKE OF THE FRONT LATE THIS AFTERNOON/TONIGHT...SOME AREAS OF MVFR CEILINGS ARE EXPECTED TO DEVELOP OVER THE FAR WEST VALLEYS...INCLUDING KJAC...AS WELL AS AREAS EAST OF THE DIVIDE...ESPECIALLY THE CODY FOOTHILLS AND JOHNSON COUNTY. && .FIRE WEATHER... A LARGE PACIFIC STORM SYSTEM WILL MOVE TOWARD THE DISTRICT TODAY. THE ASSOCIATED SURFACE COLD FRONT AND NUMEROUS SHOWERS WILL PUSH INTO AREAS WEST OF THE DIVIDE DURING THE AFTERNOON. WINDY CONDITIONS ARE EXPECTED ONCE AGAIN TODAY ALONG AND EAST OF THE DIVIDE AS THE COLD FRONT APPROACHES AND STRONG MID-LEVEL FLOW NEAR MOUNTAIN TOP SURFACES IN THE LOWER ELEVATIONS. STRONG SOUTH TO SOUTHWEST WIND AND VERY WARM TEMPERATURES ALONG WITH A DRY AIRMASS ARE ANTICIPATED THIS AFTERNOON FROM EASTERN SWEETWATER COUNTY EAST INTO NATRONA AND JOHNSON COUNTIES. THE COLD FRONT AND SCATTERED SHOWERS WILL MOVE THROUGH AREAS EAST OF THE DIVIDE THIS EVENING. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...CHURCH LONG TERM...AR AVIATION...WM FIRE WEATHER...CHURCH
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 400 AM MDT FRI MAY 28 2010 WYZ001>020-022>030-291200- ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST- BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS- EAST SWEETWATER COUNTY-FLAMING GORGE- GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS- NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN- NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS- ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES- SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN- SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY- TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN- UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN- WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST- YELLOWSTONE NATIONAL PARK- 400 AM MDT FRI MAY 28 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SOUTH TO SOUTHWEST WINDS OF 25 TO 40 MPH ALONG WITH GUSTS TO BETWEEN 40 AND 50 MPH ARE EXPECTED ONCE AGAIN TODAY FROM ROCK SPRINGS TO CASPER. ANOTHER ROUND OF UNSEASONABLY WARM TEMPERATURES WILL ACCELERATE SNOWMELT IN THE EASTERN WIND RIVER AND EASTERN BIG HORN MOUNTAINS WHERE SNOWPACK REMAINS ABOVE AVERAGE. SCATTERED TO NUMEROUS SHOWERS AND HIGH MOUNTAIN SNOW SHOWERS ALONG WITH ISOLATED THUNDERSTORMS ARE EXPECTED IN WESTERN WYOMING THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY RAIN AND MOUNTAIN SHOWERS WILL DEVELOP ACROSS MUCH OF CENTRAL AND NORTH CENTRAL WYOMING ON SATURDAY AND LINGER ACROSS NORTH CENTRAL WYOMING SUNDAY. THE SNOW LEVEL WILL DROP TO 6500 FEET ACROSS NORTHERN WYOMING LATE SATURDAY NIGHT. SNOW AMOUNTS IN THE NORTHERN MOUNTAINS OF 3 TO 6 INCHES OF ACCUMULATION WITH LOCAL AMOUNTS ABOVE 9000 FEET IN THE BIGHORN MOUNTAINS POSSIBLY GETTING MORE THAN 6 INCHES. SNOW IS ALSO EXPECTED ACROSS YELLOWSTONE NATIONAL PARK LATE TONIGHT THROUGH SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT ANY STREAMS OR RIVERS RISING RAPIDLY OR NEAR BANKFULL. SPOTTERS ARE ALSO ENCOURAGED TO REPORT WIND GUSTS OVER 40 MPH. THANK YOU. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
5 high wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2010Every state in 2010This day in weather historyWarnings in Wyoming, May 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 229251, 229252, 233720, 229250, 229249.