An upper level low and deep Pacific moisture combined to bring heavy snow to areas west of the Continental Divide. The westerly flow favored the Teton Range where the heaviest snow fell.
Every event with a place to put it; 14 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 upper level low and deep Pacific moisture combined to bring heavy snow to areas west of the Continental Divide. The westerly flow favored the Teton Range where the heaviest snow fell. Over three feet of new snow was estimated to have fallen at both the Grand Targhee and Grassy Lake SNOTEL sites. More than a foot of snow also fell in portions of the Salt River and Wyoming ranges, the Absaroka Range, and Yellowstone National Park. Favorable northwest flow aloft also brought over a foot of snow to northern portions of the western Bighorn Range. The heaviest snow in the lower elevations was at Alpine where 16.5 inches of new snow fell. Totals in Jackson Hole approached 10 inches.
East of the Divide, a tight pressure gradient and strong mid-level winds mixing to the surface brought high winds to several locations. The strongest recorded winds were near Clark, where a gust to 113 mph was measured. Measured gusts in the Green and Rattlesnake ranges and on the south side of Casper in Natrona County topped out at 88 mph and 81 mph, respectively. Peak speeds in southern Lincoln County, eastern Sweetwater County, and the Upper Wind River Basin ranged from 60 to 66 mph.
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 Jan 3, 2:33 PM MST, 11 hours 27 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 233 PM MST SAT JAN 3 2015 .SHORT TERM...TONIGHT THROUGH SUNDAY SOME LIGHT SNOW WILL LINGER IN THE EAST THIS EVENING ALONG WITH BRISK NORTH WINDS. THROUGH THE NIGHT AND SUNDAY MORNING THE FLOW ALOFT WILL SHIFT TO THE WEST NORTHWEST BRINGING INCREASED PACIFIC MOISTURE IN THE FLOW INTO WESTERN WYOMING. LIGHT SNOW WILL INCREASE SUNDAY MORNING OVER THE WESTERN MOUNTAINS. THE SNOW WILL INCREASE IN COVERAGE AND INTENSITY ACROSS THE WEST IN THE AFTERNOON. STRONG WEST SURFACE WINDS WILL MOVE IN AS WELL WITH WARMING ALONG AND NEAR THE EAST SLOPES OF THE MOUNTAINS AS DOWNSLOPE WINDS BECOME QUITE STRONG LATE IN THE AFTERNOON. .LONG TERM...SUNDAY NIGHT THROUGH SATURDAY SNOWFALL EXPECTED TO INCREASE ACROSS THE WESTERN MOUNTAINS AND VALLEYS...WITH THE POTENTIAL FOR SIGNIFICANT ACCUMULATION DURING THE EARLY PORTION OF THE FORECAST PERIOD. SOME PERIODS OF GUSTY WIND WILL ALSO BE POSSIBLE...ESPECIALLY MONDAY MORNING. THIS MAY CAUSE SOME BLOWING AND DRIFTING DURING THE MORNING COMMUTE. A WINTER STORM WATCH REMAINS IN EFFECT...WITH SNOWFALL LOOKING FAVORABLE THROUGH MONDAY NIGHT. SOME SNOWFALL WILL ALSO IMPACT NORTHERN WYOMING WITH THIS SYSTEM...ESPECIALLY ACROSS THE BIG HORN MOUNTAINS AND JOHNSON COUNTY. EXPECT A RETURN OF COLDER TEMPERATURES...THOUGH NOT AS COLD AS THE MOST RECENT SURGE OF ARCTIC AIR. SNOWFALL MAY LINGER ACROSS NORTHERN WYOMING AS MOISTURE CONTINUES TO RIDE OVER THE APPROACHING RIDGE OF HIGH PRESSURE. SLIGHTLY WARMER TEMPERATURES ARE ANTICIPATED AS THE INFLUENCING SYSTEM MOVES FURTHER EASTWARD. THE LINGERING MOISTURE WILL WEAKEN WEDNESDAY AFTERNOON... WITH WIDESPREAD DRY CONDITIONS. THE APPROACHING RIDGE OF HIGH PRESSURE WILL MOVE OVER THE STATE BY WEDNESDAY MORNING...WITH DRY CONDITIONS AND WARMING TEMPERATURES ANTICIPATED THROUGH LATE THURSDAY. MODELS BEGIN TO LOSE THEIR AGREEMENT FRIDAY MORNING AFTER THE DEPARTURE OF THE RIDGE OF HIGH PRESSURE. THE GFS INDICATES ANOTHER ROUND OF FAIRLY WIDESPREAD SNOWFALL...WHILE THE ECMWF MAINTAINS ITS DRIER SOLUTION. A MIDDLE GROUND IS CONVEYED IN THIS FORECAST IN THE EXTENDED TIME FRAME. && .AVIATION.../00Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES A STRONG COLD FRONT WILL PUSH SOUTH DURING THE AFTERNOON WITH A PERIOD OF SNOW BEHIND IT. MVFR TO IFR CEILINGS AND VISIBILITIES REDUCED IN SNOW...FOG AND BLOWING SNOW WILL BEGIN TO DECREASE FROM NORTHWEST TO SOUTHEAST FROM 00Z TO 03Z WITH VFR CONDITIONS BECOMING PREVAILING BY 03Z. FROM 18Z TO 00Z MONDAY OVER THE MOUNTAINS ALONG AND EAST OF THE CONTINENTAL DIVIDE...AREAS OF MVFR TO IFR CEILINGS WITH VISIBILITIES REDUCED IN SNOW ...FOG AND BLOWING SNOW WILL BECOME MORE WIDESPREAD AS A PACIFIC STORM MOVES EAST INTO THE AREA. STRONG WINDS WILL ALSO PRODUCE AREAS OF LOW LEVEL WIND SHEAR OVER AND NEAR THE EAST SLOPES OF THE MOUNTAINS. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES OVER THE MOUNTAINS AREAS OF MVFR TO IFR CEILINGS AND VISIBILITIES REDUCED IN SNOW...FOG AND BLOWING SNOW WILL DECREASE FROM NORTHWEST TO SOUTHEAST FROM 00Z TO 03Z WITH VFR CONDITIONS BECOMING PREVAILING BETWEEN 03Z AND 06Z. FROM 18Z TO 00Z MONDAY AREAS OF MVFR TO IFR CEILINGS WITH VISIBILITIES REDUCED IN SNOW ...FOG AND BLOWING SNOW WILL BECOME WIDESPREAD AS A PACIFIC STORM MOVES EAST INTO THE AREA. STRONG WINDS WILL ALSO PRODUCE AREAS OF LOW LEVEL WIND SHEAR OVER AND NEAR THE MOUNTAINS. OVERALL VFR CONDITIONS WILL PREVAIL OVER THE SOUTHWEST WITH LOCAL MVFR TO IFR CONDITIONS MAINLY OVER THE HIGHER TERRAIN. && .FIRE WEATHER... WIDESPREAD SNOW COVER AND COLD TEMPERATURES WILL CONTINUE ACROSS THE AREA. A LONG DURATION HEAVY SNOW EVENT IS EXPECTED TO DEVELOP OVER THE WEST SUNDAY AFTERNOON AND CONTINUE THROUGH MONDAY NIGHT. STRONG WEST WINDS WILL ACCOMPANY THIS STORM. EAST OF THE CONTINENTAL DIVIDE STRONG DOWNSLOPE WINDS WILL PRODUCE WARMING MOST AREAS. GENERALLY THE MIXING HEIGHTS WILL BE LOW WITH POOR SMOKE DISPERSAL...HOWEVER THE WINDIER AREAS WILL HAVE FAIR TO GOOD SMOKE DISPERSAL IN THE AFTERNOON HOURS SUNDAY AND MONDAY. && .RIW WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH LATE MONDAY NIGHT WYZ001-002-012>015-023>025. && SHORT TERM...C.BAKER LONG TERM...BRANHAM AVIATION...C.BAKER FIRE WEATHER...C.BAKER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 1024 PM MST SAT JAN 3 2015 WYZ001>020-022>030-041200- 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- 1024 PM MST SAT JAN 3 2015 ...WINTER STORM WATCH FOR THE WESTERN AND NORTHWESTERN MOUNTAINS AND VALLEYS BEGINNING SUNDAY EVENING AND LASTING UNTIL TUESDAY MORNING... ...HIGH WIND WATCH FOR PORTIONS OF CENTRAL WYOMING BETWEEN SOUTH PASS AND CASPER BEGINNING LATER SUNDAY NIGHT AND CONTINUING THROUGH THE DAY ON MONDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT TODAY AND TONIGHT...A WINTER WEATHER SYSTEM ALONG WITH A NEW COLD FRONT WILL CONTINUE LIGHT SNOW IN THE WESTERN MOUNTAINS TODAY. LIGHT TO OCCASIONALLY MODERATE SNOW WILL SPREAD EAST OF THE DIVIDE...COMBINING WITH INCREASED NORTHERLY WINDS AND REDUCING VISIBILITY AT TIMES IN BLOWING SNOW. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SUNDAY MORNING THROUGH TUESDAY...THE NEXT AND MORE POTENT AND PROLONGED WINTER WEATHER SYSTEM WILL IMPACT MAINLY THE WESTERN AND NORTHERN MOUNTAINS...WITH AREAS OF SIGNIFICANT SNOW POSSIBLE. HIGH WINDS WILL ALSO BE POSSIBLE ACROSS PORTIONS OF CENTRAL WYOMING FROM SUNDAY NIGHT THROUGH THE DAY ON MONDAY. PLEASE SEE CURRENT WINTER WEATHER PRODUCTS FOR MORE INFORMATION. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT SNOW AMOUNTS AND HIGH WIND SPEEDS OR DAMAGE. THANK YOU. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
8 winter storm, 6 high wind. Local standard time, as filed.
Very heavy snow fell in portions of the Tetons. The highest amounts were recorded at the Grand Targhee and Grassy Lake SNOTEL stations. In addition, 33 inches of new snow was measured on top of the Jackson Hole Ski Resort.
Trained spotters reported heavy snow in much of the Jackson Valley. Nearly 10 inches of new snow fell at Moose and Jackson.
Heavy snow fell in portions of the Star Valley. The heaviest snow fell at Alpine where 16.5 inches of new snow was measured. Farther south, 6 inches of snow was measured at Afton where warmer air caused the snow to mix with rain at times.
Heavy snow fell in the Salt and Wyoming Ranges. The highest total was 21 inches at the Spring Creek Divide SNOTEL site.
The SNOTEL station at Evening Star estimated 26 inches of new snow. The Wolverine SNOTEL had 19 inches.
The SNOTELs at Sylvan Lake and Two Ocean Plateau recorded an estimated 19 inches of new snow.
Wind gusts of 88 mph were reported at both the Fales Rock and Camp Creek RAWS stations.
A trained spotter measured 7 inches of new snow at Bondurant.
The SNOTEL site at Shell Creek estimated 16 inches of new snow.
High winds blew on the south side of Casper. The weather sensor at Outer Drive recorded many wind gusts past 58 mph with a maximum of 81 mph.
Very strong winds occurred in the vicinity of Clark. The wind sensor 5 miles west of Clark had several wind gusts above hurricane force, including a maximum of 113 mph.
Numerous wind gusts over 58 mph were recorded at the Snow Springs Creek RAWS including a maximum of 66 mph. The Rock Springs Airport ASOS had a wind gust of 59 mph at 0524MST and 1146MST.
A wind gust of 61 mph was recorded at the Dubois Elementary School.
The AWOS at the airport near Kemmerer recorded a wind gust of 60 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2015Every state in 2015This day in weather historyWarnings in Wyoming, January 2015
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: 549862, 549863, 549865, 549866, 549868, 549861, 549870, 549867, 549869, 549871, 549872, 549875, 549873, 549874.