An avalanche was triggered by a snowmobile rider on Grouse Mountain around 1530MST on February 27. The avalanche occurred on a 38 degree slope in an area known as Drag Race Hill.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RIW wrote it up.
An avalanche was triggered by a snowmobile rider on Grouse Mountain around 1530MST on February 27. The avalanche occurred on a 38 degree slope in an area known as Drag Race Hill. The snowmobile rider was highmarking on the hill when he triggered the slide and was buried under four to five feet of snow for about 20 minutes. Rangers attempted to rescue the snowmobiler but declared him deceased after more than an hour.
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 Feb 27, 10:57 AM MST, 4 hours 33 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE RIVERTON WY 1057 AM MST MON FEB 27 2012 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT LIGHT SNOWFALL IS EXPECTED TO DEVELOP OVER THE SOUTHWESTERN MOUNTAINS THIS AFTERNOON...THE FIRST ROUND OF PRECIPITATION ASSOCIATED WITH A LARGER SYSTEM. WHILE MODELS ARE NOT AS SUPPORTIVE WITH THE DEVELOPMENT OF THIS INITIAL ROUND OF SNOWFALL...MODELS DO INDICATE INCREASED ISENTROPIC LIFT DURING THE EARLY MORNING HOURS. SNOWFALL IS EXPECTED TO INCREASE IN SIGNIFICANCE DURING THE AFTERNOON HOURS TODAY AS A STRONG AREA OF LOW PRESSURE MOVES ACROSS CALIFORNIA AND INTO THE DESERT SOUTHWEST. THE SOUTHWEST FLOW OVER THE AREA...WHICH WILL MOVE MOISTURE INTO THE FORECAST AREA EFFICIENTLY...WILL REMAIN OVER THE CWA THROUGH THE OVERNIGHT HOURS WHILE THE AREA OF LOW PRESSURE MOVES THROUGH THE DESERT SOUTHWEST...REACHING INTO SOUTHERN UTAH BY EARLY TUESDAY MORNING. SNOWFALL ACROSS THE FORECAST AREA WILL INCREASE AND SPREAD TONIGHT AND TOMORROW. MODELS CONTINUE TO INDICATE THE HEAVIEST ROUNDS OF SNOWFALL WILL BE TUESDAY MORNING AND AFTERNOON. THIS HEAVIER SNOWFALL IS PARTNERED WITH THE AREA OF LOW PRESSURE LIFTING QUICKLY NORTHEAST THROUGH COLORADO AND WYOMING AND INTO THE NORTHERN PLAINS BY TUESDAY EVENING. THE EXACT TRACK OFF THE LOW PRESSURE SYSTEM STILL VARIES DEPENDING ON WHICH MODEL IS BEING INTERROGATED. THE GFS SEEMS TO BE THE FAVORED MODEL FOR THE GIVEN SYSTEM...WHICH TAKES A SLIGHTLY MORE SOUTHERN ROUTE THAN THE NAM. SNOWFALL AMOUNTS IN THE CURRENT FORECAST PACKAGE DO NOT VARY SIGNIFICANTLY FROM THE DAYTIME FORECAST. WIDESPREAD WINTER WEATHER ADVISORY AMOUNTS ARE INDICATED...TRANSLATED AS 6 TO 12 INCHES IN THE MOUNTAINS...WITH 2 TO 5 INCHES IN THE VALLEYS. THE QUESTION AREA CONTINUES TO BE NATRONA COUNTY. NATIONAL GUIDANCE SUPPORTS THE POTENTIAL FOR 1 TO 3 INCHES OVER THE AREA...WITH HEAVIER SNOWFALL AMOUNTS LIKELY ACROSS NORTHERN JOHNSON COUNTY AS THE SYSTEM MOVES NORTHEAST OF THE CWA. BECAUSE THIS SYSTEM IS NOT EXPECTED TO SEE MUCH SNOWFALL UNTIL LATE MONDAY AFTERNOON AND EVENING...WILL HOLD OFF ON ISSUANCE OF ANY WINTER WEATHER HIGHLIGHTS IN HOPES..AGAIN...THAT MODELS WILL REACH A BETTER AGREEMENT AS THE SYSTEM MOVES ONSHORE. THIS SYSTEM...WHICH IS THE IMMEDIATE CHALLENGE IN THE FORECAST PERIOD IS NOT THE ONLY POTENTIALLY SIGNIFICANT SYSTEM. THE DEPARTURE OF THE AFOREMENTIONED AREA OF LOW PRESSURE WILL ALLOW A TRANSITORY RIDGE OF HIGH PRESSURE OVER THE AREA FOR WEDNESDAY. HOWEVER...ANOTHER STRONG...PACIFIC LOW PRESSURE SYSTEM BEGINS TO MOVE ONSHORE WEDNESDAY...WHICH BEGINS TO PUSH SNOWFALL ACROSS WESTERN WYOMING WEDNESDAY AFTERNOON AND EVENING. THIS SYSTEM...WHICH SHOWS POTENTIAL SIGNATURES OF BEING SIGNIFICANT...WILL CONTINUE TO BE MONITORED AS IT APPROACHES WYOMING. .LONG TERM...THURSDAY THROUGH MONDAY MEDIUM RANGE MODELS ARE IN FAIRLY GOOD AGREEMENT ON BRINGING A BROAD TROUGH ACROSS THE INTERMOUNTAIN WEST THROUGH THURSDAY...WITH WIDESPREAD SNOWFALL ACROSS WESTERN AND SOUTHERN WYOMING AS A COLD FRONT PUSHES EAST ACROSS WYOMING. DOWNSLOPE WINDS SHOULD KEEP MOST AREAS EAST OF THE DIVIDE FAIRLY DRY DURING THIS TIME FRAME. BREEZY TO WINDY CONDITIONS CAN ALSO BE EXPECTED ACROSS THE WIND CORRIDOR FROM ROCK SPRINGS TO CASPER. THE MAJORITY OF THE PRECIPITATION ASSOCIATED WITH THE DYNAMICS OF THIS SYSTEM SHOULD TAPER OFF THURSDAY NIGHT...LEAVING ONLY OROGRAPHIC PRECIPITATION IN THE NORTHWEST FLOW BEHIND THIS SYSTEM. THIS NORTHWEST FLOW WILL CONTINUE FRIDAY AND SATURDAY...WITH BREEZY TO WINDY CONDITIONS CONTINUING IN THE USUAL WIND PRONE LOCATIONS...ESPECIALLY SATURDAY. THE ECMWF SHOWS A REINFORCING SHORTWAVE MOVING OUT OF CANADA ALONG THE BACKSIDE OF THE MAIN TROUGH FRIDAY NIGHT INTO SATURDAY...POSSIBLY BRINGING A QUICK SHOT OF SNOW ACROSS THE STATE. HAVE INCREASED POPS IN THE WESTERN AND NORTHERN MOUNTAINS TO REFLECT THIS. HOWEVER LEFT LOW ELEVATION POPS EAST OF THE DIVIDE ALONE DUE TO THE MODEL DIFFERENCES...THIS WILL NEED TO BE WATCHED BY FUTURE SHIFTS. MODELS CONTINUE TO HINT AT THE DEVELOPMENT OF A SHORT-LIVED RIDGE SUNDAY...WITH THE GFS INDICATING A BROAD...SLOW...AND LOW AMPLITUDE RIDGE FOLLOWED BY A BROAD TROUGH MOVING INTO THE WESTERN CONUS. THE ECMWF BRINGS A SLIGHTLY HIGHER AMPLITUDE RIDGE...FOLLOWED QUICKLY BY A FAST MOVING TROUGH ON MONDAY. HAVE BROAD-BRUSHED POPS FOR NOW WITH A SLIGHT NUDGE TOWARDS TOWARDS THE EUROPEAN SOLUTION IN THE WESTERN MOUNTAINS BASED ON CURRENT HPC GUIDANCE. OVERALL...TEMPERATURES WILL BE A BIT BELOW AVERAGE DURING THE EXTENDED...ESPECIALLY THURSDAY AND FRIDAY. HOWEVER...EXTREME TEMPERATURES ARE NOT EXPECTED. .AVIATION.../18Z ISSUANCE/ VFR CONDITIONS WILL PREVAIL THROUGH 03Z. SOME LIGHT SNOW IS DEVELOPING ACROSS THE WEST...WITH LOWER CONDITIONS MAINLY OVER THE MOUNTAINS THROUGH THE EVENING. MVFR TO LIFR CIGS AND VSBY WILL DEVELOP OVER MUCH OF THE WEST AND SOUTHWEST AFTER 03Z AND SPREAD NORTHEAST INTO CENTRAL WYOMING BY 06Z TUE. AFTER 06Z THE SNOW WILL SPREAD INTO NORTHERN WY WITH CONDITIONS LOWERING TO MVFR BY 12Z TUE. SNOW MAY BECOME MORE SHOWERY LATE TUESDAY MORNING...AND COULD BE HEAVY AT TIMES. WIND SPEEDS WILL NOT HAVE MUCH OF AN IMPACT UNTIL AFTER 18Z TUE. .FIRE WEATHER... GENERALLY BENIGN CONDITIONS EXPECTED THIS MORNING...WITH SNOWFALL INCREASING OVER THE WESTERN MOUNTAINS AND VALLEYS THROUGH THE MORNING AND AFTERNOON. MODERATELY SIGNIFICANT SNOWFALL IS POSSIBLE ACROSS MUCH OF THE FORECAST AREA AS THIS SYSTEM CONTINUES TO SPREAD EAST. THE MAJORITY OF THE FORECAST AREA WILL EXPERIENCE THE OPPORTUNITY FOR SNOWFALL. MANY AREAS WILL SEE THE POTENTIAL FOR 2 TO 4 INCHES OF SNOWFALL BY TUESDAY EVENING...WITH MOUNTAIN LOCATIONS SEEING THE POTENTIAL OF 4 TO 10 INCHES. THE EXCEPTION MAY BE NORTH BIG HORN BASIN WHERE SNOWFALL IS NOT EXPECTED TO BE AS SIGNIFICANT. CONDITIONS WILL IMPROVE LATE THURSDAY NIGHT AND CONTINUE INTO WEDNESDAY MORNING UNDER THE PRESENCE OF A BRIEF RIDGE OF HIGH PRESSURE. THEN ANOTHER...ALSO POTENTIALLY SIGNIFICANT...WINTER SYSTEM MAY BEGIN TO IMPACT WESTERN WYOMING BY WEDNESDAY AFTERNOON. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...BRANHAM LONG TERM...WOLCOTT AVIATION...ALLEN FIRE WEATHER...BRANHAM
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 319 PM MST MON FEB 27 2012 WYZ001>020-022>030-281400- 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- 319 PM MST MON FEB 27 2012 ...WINTER WEATHER ADVISORIES TONIGHT AND TUESDAY FOR SOUTHERN CENTRAL AND NORTHERN WYOMING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SNOWFALL...WHICH MAY BE HEAVY AT TIMES WILL DEVELOP THIS EVENING ACROSS WESTERN AND SOUTHERN WYOMING. SNOWFALL WILL CONTINUE TO SPREAD ACROSS MUCH OF THE FORECAST AREA THROUGH THE OVERNIGHT HOURS. ONGOING SNOWFALL MAY RESULT IN SLICK AND SNOW PACKED ROADS. MOTORISTS SHOULD CONSULT ROAD CONDITIONS BEFORE TRAVELING TONIGHT. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY TUESDAY...ANOTHER STRONG STORM SYSTEM WILL LIKELY SPREAD SIGNIFICANT SNOWFALL FROM WEST TO EAST ACROSS THE AREA WITH THE POTENTIAL FOR MODERATE AMOUNTS OF SNOW. WEDNESDAY AND THURSDAY...SIGNIFICANT SNOWFALL POSSIBLE ALONG AND WEST OF THE DIVIDE. FRIDAY AND SATURDAY...STRONG WINDS POSSIBLE ACROSS THE WIND CORRIDOR FROM ROCK SPRINGS TO CASPER. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 330 PM MST MON FEB 27 2012 WYZ001-012-013-023-024-027-281100- JACKSON HOLE-SALT RIVER AND WYOMING RANGES-SOUTH LINCOLN COUNTY- STAR VALLEY-TETON AND GROS VENTRE MOUNTAINS- YELLOWSTONE NATIONAL PARK- 330 PM MST MON FEB 27 2012 ...HEAVY SNOW AND WIND EXPECTED EARLY WEDNESDAY THROUGH WEDNESDAY NIGHT... A PACIFIC STORM WILL MOVE EAST FROM THE PACIFIC NORTHWEST LATE TUESDAY NIGHT WITH SNOWFALL AND WIND EXPECTED TO INCREASE SIGNIFICANTLY EARLY WEDNESDAY MORNING ACROSS WESTERN WYOMING. SNOWFALL MAY BECOME HEAVY THROUGH THE DAY WEDNESDAY WITH WEST WINDS OF 25 TO 35 MPH WITH STRONG GUSTS DEVELOPING ON THE PASSES AND HIGHER RIDGES AND PEAKS. SNOWFALL MAY BE IN THE 10 TO 15 INCH RANGE IN THE MOUNTAINS WITH LOCAL AMOUNTS UP TO 20 INCHES IN THE TETONS. THE VALLEYS OF THE WEST MAY SEE 5 TO 10 INCHES OF SNOW WITH BLOWING AND DRIFTING SNOW OVER OPEN AREAS. AS THE START OF THIS STORM MOVES CLOSER...MORE SPECIFIC SNOWFALL AMOUNTS SHOULD BE AVAILABLE. C.BAKER
The national radar mosaic for the moment the first event began.
1 avalanche. Local standard time, as filed.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Avalanche, Teton & Gros Ventre Mountains | 2012-02-27 | 35 | Male | Outside/Open Areas | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2012Every state in 2012This day in weather historyWarnings in Wyoming, February 2012
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: 361137.