A plume of Pacific moisture rode over a dome of very cold air at this surface. With good jet dynamics in place, portions of southern Wyoming saw periods of heavy snow.
Every event with a place to put it; 8 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.
A plume of Pacific moisture rode over a dome of very cold air at this surface. With good jet dynamics in place, portions of southern Wyoming saw periods of heavy snow. The heaviest snow fell in Lincoln County where many locations received a foot or more of new snow. Heavy snow also fell in Sweetwater County with 6 to 10 inches commonplace along the Interstate 80 corridor.
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, 10:32 AM MST, 1 hour 28 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1032 AM MST Tue Jan 3 2017 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT THE ARCTIC FRONT IS STILL STALLED OUT OVER SOUTH CENTRAL WYOMING. NORTH OF THE FRONT TEMPERATURES RANGE FROM ZERO TO 12 BELOW AND SOUTH OF THE FRONT IN SWEETWATER COUNTY TEMPERATURES ARE STILL IN THE TEENS. THE FAR WEST VALLEYS ARE HAVE TEMPS HOVERING AROUND 10 DEGREES. ISENTROPIC LIFT OCCURRING UP AND OVER THE COLD DOME IS PRODUCING PATCHY LIGHT SNOWFALL ACROSS THE CWA BUT SHOULD BE MORE FOCUSED IN SWEETWATER COUNTY. ANY THIN STRATOCU OUT THERE ARE PRODUCING SNOWFLAKES AT THESE COLD TEMPS. AS LONG AS THE TEMPS A FEW THOUSAND AGL ARE 14F DEGREES OR COLDER, ICE CRYSTALS WILL FORM IN ANY THIN LOW CLOUDS THAT FORM AND WILL PRODUCE FLURRIES AT THE VERY LEAST, ESPECIALLY IF THEY DO NOT HAVE THAT FAR TO FALL FROM THE LOW CLOUD BASES BEFORE EVAPORATING. HOWEVER, AN INCH OF SNOW COULD ACCUMULATE ALONG AND SOUTH OF INTERSTATE 80 TONIGHT ALONG WITH TWO INCHES POSSIBLE NEAR THE COLORADO STATE LINE BEFORE SUNRISE WITH THE INFLUENCE OF THE LEFT FRONT QUAD OF THE STRONGER SOUTHERN BRANCH OF THE JET TO THE SOUTH. THIS TREND OF PATCHY LIGHT SNOW WILL CONTINUE TODAY THROUGH TONIGHT BUT WITH LESS SNOWFALL OVER SWEETWATER. ALTHOUGH SNOWFALL WILL INCREASE OVER THE STAR VALLEY AND SALT RIVER RANGE THIS AFTERNOON WITH THE INFLUENCE OF THE RIGHT ENTRANCE REGION OF THE JET MAX AS WELL AS FAVORABLE UPSLOPE FLOW. THEN LATE TONIGHT AND WEDNESDAY, A SOUTHEAST BOUND VORT LOBE WILL GLANCE WYOMING TO THE NORTHEAST WITH COLDER AIR ADVECTING IN FROM THE NORTH WITH H7 TEMPS DROPPING TO -20C. IN ADDITION, A MID LEVEL CIRCULATION WILL ESTABLISH ITSELF ALONG THE WESTERN WYOMING BORDER AND WILL WOBBLE AROUND THERE FROM WEDNESDAY THROUGH THURSDAY BEFORE TRACKING SOUTHEAST TO COLORADO, THUS RESULTING IN DEEPENING UPSLOPE FLOW EAST OF THE DIVIDE. THESE DYNAMICS ALONG WITH WIDESPREAD ISENTROPIC LIFT WILL RESULT IN HIGH POPS SPREADING NORTHEAST TO ENCOMPASS MOST OF THE CWA FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY, BEFORE BEGINNING TO RETREAT SOUTHWEST WEDNESDAY NIGHT, AND INTO THURSDAY MORNING. SOUTHWEST WYOMING STAND THE BEST CHANCE OF ACCUMULATING SNOWFALL ACROSS THE CWA GIVEN THE AFOREMENTIONED DYNAMICS AS WELL AS THE FRONTAL BOUNDARY BEING IN THE VICINITY, UPPER LEVEL DIVERGENCE, LOW LEVEL CONVERGENCE, JET DYNAMICS INVOLVING SEVERAL JET SPEED MAXES, QG FORCING AND GOOD OMEGA ALL CONTRIBUTING TO THE HEAVY SNOWFALL, NOT TO MENTION FAVORABLE DENDRITIC GROWTH. WILL BE ISSUING A WINTER STORM WATCH FOR SOUTHWEST WYOMING VALID FROM 09Z TONIGHT THROUGH 18Z THURSDAY. HOWEVER WILL START OFF THE STAR VALLEY AND ADJACENT SALT AND WYOMING RANGES THIS AFTERNOON AT 21Z. THERE COULD BE AS MUCH AS 12 TO 16 INCHES OF SNOW IN THE SALT RIVER RANGE BY MID DAY THURSDAY. THE EAST WEST TROUGH THAT WILL REMAIN ALONG THE PACIFIC NW COAST TO MONTANA FOR THE NEXT COUPLE OF DAYS WILL EVENTUALLY ACCELERATE AS AN OPEN TROUGH AND TRACK SOUTHEAST ACROSS SOUTHWEST WYOMING THURSDAY NIGHT SO WILL KEEP LINGERING POPS THU NT BUT KEEP THE IDEA OF TRENDING THE POPS BACK TOWARD THE SOUTHWEST. AS FOR THE COLD TEMPERATURES FOR THE NEXT FEW DAYS, IT APPEARS THE COLDEST MORNING OF THE WEEK FOR MOST AREAS WILL BE ON THURSDAY MORNING AS WE EXPERIENCE PARTIAL CLEARING FROM NE TO SW WITH LOWS APPROACHING 25 BELOW IN YNP AS WELL AS IN THE BIG HORN BASIN WITH TEMPS NOT QUITE AS COLD ELSEWHERE ACROSS THE CWA. .LONG TERM...FRIDAY THROUGH TUESDAY Shortwave ridging moves in for a couple days behind our midweek storm which will result in inversions for our basins and valleys (with bitter cold temps) while mtns/foothills start to warm. Upper level low which drops into the srn Gulf of Alaska/Ern Pacific helps to pump this ridge up for a couple days. This low originates from a very cold disturbance out between Kamchatka and Siberia. Eventually this low gets kicked ewd and opens up with a period of significant snow west of the divide late in the weekend into early next week. The wind corridor and Cody Foothills will moderate with winds returning ahead of and with this system impacting the west. All east slope foothills areas may see warning in this scenario while basins hope to finally get some mixing if gradient increases enough. && .AVIATION.../18Z ISSUANCE/ West of the divide...KBPI/KJAC/KPNA/KRKS Terminals Scattered areas of light snow will occur this afternoon. Expect some MVFR/IFR conditions at times along with some mountain obscuration. Snow will increase from west to east after 03Z tonight and continue through 13Z for all TAF sites with MVFR and local IFR conditions along with frequent mountain obsurations. Conditions will gradually improve after 13Z from west to east as the storm moves away. East of the divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals Areas of low clouds and flurries will create MVFR conditions in places through 20Z followed by gradually improving conditions. A system approaching from the west will bring local MVFR conditions along with areas of light snow along and south of a line approximately 20 miles north of KRIW to KCPR late tonight and into tomorrow morning. && .FIRE WEATHER... TEMPERATURES WILL REMAIN RELATIVELY UNCHANGED THROUGH THURSDAY AND ON THE COLD SIDE. THE COLDEST MORNING SHOULD BE ON THURSDAY MORNING WHEN LOW TEMPERATURES WILL APPROACH 25 BELOW IN ZONE 140 AND IN THE BIG HORN BASIN. OTHERWISE, LOW TEMPERATURES WILL GENERALLY RANGE FROM ZERO TO 20 BELOW OVER THE NORTH HALF OF WYOMING AND ZERO TO 10 SOUTH THROUGH THURSDAY NIGHT. HIGHS TODAY THROUGH THURSDAY WILL RANGE FROM ZERO TO 10 IN THE NORTH TO THE TEENS AND 20S SOUTH. AN EXTENDED PERIOD OF SNOWFALL CAN BE EXPECTED FROM TODAY THROUGH THURSDAY NIGHT WITH THE MORE SIGNIFICANT SNOWFALL SPREADING FROM SOUTHWEST TO NORTHEAST THROUGH WEDNESDAY BEFORE RETREATING BACK TO THE SOUTHWEST THROUGH THURSDAY AND THURSDAY NIGHT. SUBSTANTIAL SNOWFALL ACCUMULATIONS ARE EXPECTED IN SOUTHWEST WYOMING DURING THIS TIME FRAME, WITH SNOWFALL AMOUNTS TAPERING OFF AS ONE TRAVELS NORTHEAST ACROSS WYOMING THIS WEEK. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from 2 PM MST this afternoon through Thursday morning for WYZ023-024. Winter Storm Watch from late tonight through Thursday morning for WYZ026>030. && SHORT TERM...Lipson LONG TERM...Skrbac AVIATION...Hattings FIRE WEATHER...Lipson
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 352 AM MST TUE JAN 3 2017 WYZ001>020-022>030-041200- YELLOWSTONE NATIONAL PARK-ABSAROKA MOUNTAINS-CODY FOOTHILLS- NORTH BIG HORN BASIN-SOUTHWEST BIG HORN BASIN- SOUTHEAST BIG HORN BASIN-OWL CREEK AND BRIDGER MOUNTAINS- BIGHORN MOUNTAINS WEST-BIGHORN MOUNTAINS SOUTHEAST- NORTHEAST JOHNSON COUNTY-SOUTHEAST JOHNSON COUNTY- TETON AND GROS VENTRE MOUNTAINS-JACKSON HOLE- WIND RIVER MOUNTAINS WEST-WIND RIVER MOUNTAINS EAST- UPPER WIND RIVER BASIN-WIND RIVER BASIN-LANDER FOOTHILLS- GREEN MOUNTAINS AND RATTLESNAKE RANGE- NATRONA COUNTY LOWER ELEVATIONS-CASPER MOUNTAIN-STAR VALLEY- SALT RIVER AND WYOMING RANGES-UPPER GREEN RIVER BASIN FOOTHILLS- UPPER GREEN RIVER BASIN-SOUTH LINCOLN COUNTY- ROCK SPRINGS AND GREEN RIVER-FLAMING GORGE-EAST SWEETWATER COUNTY- 352 AM MST TUE JAN 3 2017 ...WINTER STORM WATCH FOR SOUTHWEST WYOMING FROM LATE THIS AFTERNOON THROUGH THURSDAY MORNING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SNOW, HEAVY AT TIMES WILL DEVELOP THIS AFTERNOON OVER THE STAR VALLEY AND SALT AND WYOMING RANGES BY 2 PM THIS AFTERNOON. THEN SNOW, HEAVY AT TIMES WILL DEVELOP OVER THE REST OF SOUTHWEST WYOMING BEGINNING AT 2 AM LATE TONIGHT. PLEASE SEE THE LATEST WINTER STORM WATCH FOR MORE INFORMATION CONCERNING THIS WINTER WEATHER EVENT. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY WEDNESDAY AND THURSDAY...COLD WITH AREAS OF LIGHT TO MODERATE SNOW...EXCEPT IN SOUTHWEST WYOMING WHERE SNOW WILL BE HEAVY AT TIMES WEDNESDAY THROUGH THURSDAY MORNING. MOST AREAS WILL ONLY SEE SINGLE DIGITS, TEENS, AND LOW 20S FOR HIGHS WITH LOWS 10 TO 20 BELOW ZERO IN THE NORTH HALF OF WYOMING ALONG WITH LOCALLY COLDER READINGS. LOW TEMPERATURES WILL BE ABOVE ZERO IN THE SOUTH. .SPOTTER INFORMATION STATEMENT... SPOTTER ARE ENCOURAGED TO REPORT SNOWFALL AMOUNTS...THANK YOU. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
8 winter storm. Local standard time, as filed.
A CocoRaHS observer measured 6 inches of new snow 5 miles north of Farson.
Heavy snow fell in portions of the Salt and Wyoming Range. Some of the higher totals included 17 inches at Commissary Ridge and 14 inches at the Hams Fork SNOTEL.
Heavy snow fell through much of the Star Valley. Some totals included 11 inches in Afton and 13 inches in Alpine.
At Fossil Butte, eight inches of new snow was measured.
New snowfall amounts of 6 to 10 inches were common across Green River and Rock Springs, including 11.4 inches 4 miles NNW of Rock Springs.
The CoCoRaHS observer at Buckboard Marina measured 8 inches of new snow.
A trained spotter measured 6 inches of new snow at Wamsutter.
A trained spotter reported 7.4 inches of snow at Daniel.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2017Every state in 2017This day in weather historyWarnings in Wyoming, January 2017
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: 669753, 669751, 669750, 669752, 669754, 669755, 669756, 669757.