Warming temperatures melted a substantial snow pack across the lower elevations of western Sweetwater County. This snow melting, combined with ice jams, brought flooding along the Blacks Fork River from Little America through Granger .
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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.
Warming temperatures melted a substantial snow pack across the lower elevations of western Sweetwater County. This snow melting, combined with ice jams, brought flooding along the Blacks Fork River from Little America through Granger . The river crested between 12.5 and 13 feet at the Little America flood gauge, which is a record level. A mobile home park along the river was evacuated for a couple of days. However, little or no damage was done and other flooding was restricted to low lying areas and dirt roads along the river. The river began dropping on March 12th and fell below flood stage on March 15th.
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 Mar 10, 2:30 AM MST, 7 hours 30 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 230 AM MST Fri Mar 10 2017 .SHORT TERM...Today through Sunday night Imagery showing a flat trof across the ern CONUS and a modest ridge over the west. The jet follows this upper pattern from WA on the west through MT NS and MN before diving swd through the upper midwest then east and across mid-Atlantic/New England. Embedded SW/jet streak still upstream moving into/through the PAC NW. Modest EPAC moisture continues to flow across the NW CONUS and into portions of wrn WY. SFC has post frontal high P across the High and Northern/Central Plains with a backdoor nearly stationary front draped along the Continental Divide in WY and lower pressure to the west of the front. Precipitation, both frozen and liquid, is currently falling lightly across the nw quad of WY. Today, A Winter Storm Warning continues for zones 1 and 12 across nwrn WY with areas of Advisories surrounding the Warning. Through early this evening, anywhere from 1 to 10 inches of accumulating snowfall has fallen across the highlighted areas...with lowest amounts across the southwestern mountains and highest amounts over Teton and Park counties. Generally from a trace to a couple of inches has fallen in the valleys below 7k ft. Otherwise, weak ridging across the wrn CONUS continues to slide eastward, further flattening ahead of and with the fast moving embedded SW/jet streak that will race into/across the western and northern FA late this morning and afternoon...enhancing snowfall rates one more time before the wave and associated front clear the area by evening with precipitation quickly ending across the west. While accumulating snow above 7000 ft is most probable to continue, below that elevation in the valleys will continue to struggle to produce snow under relatively warm (mid 30s deg F) and nearly saturated lower levels combine (no evaporative cooling). Therefore, snow amounts in the valleys continue to be hard to predict at this time. The best period for accumulating snowfall, if at all below 7k ft in the valleys, will probably arrive late this morning and afternoon with some slight mid-level cooling moving into the area west of the Divide with the aforementioned Sw/jet streak. That said, total snowfall for this event over the mountains of the area through today will generally range from 10 to 24 inches for much of the warned region with to 4 to 14 inches with the Advisories...much of this elevation and temperature dependent. Tonight through Saturday night, rain/sn showers ending across the west with a few new showers possible east of the Divide and across southern WY as the embedded SW/jet continues quickly across WY. Best chances for measurable precip/light snow will occur with a clipper type frontal passage across nern WY...mainly affecting portions of Johnson county. This may also impact portions of I90 and I25 for a short period. Saturday, upper ridging returns to the forecast area and the atmosphere drys out ahead of another upstream SW trof that will be lurking just offshore the PAC NW. This wave should arrive near nw WY later Saturday night with the nose of yet another jet closely following and arriving early Sunday morning. Precip chances over nw WY begin to rise once again as new moisture runs into the terrain. Colder airmass should be able to get snow to the valley floors in this case. Sunday and Sunday night, with the FA under upper NW flow and a strong embedded wave/jet moving across the area...strong cyclogenesis is probable across eastern Colorado with frontogenesis and push occurring well to the north of WY...accelerating down south through the FA as the cyclone spins up Sunday afternoon. Snowfall with quickly end across the west while blustery areas of wind and isolated to scattered showers...rain and snow...race across the ea stern CWA. All precipitation should be leaving or mostly gone Sunday night. .LONG TERM...Monday through Friday Models continue to show a mean ridge over the Rockies through much of the work week with above average temperatures, and mainly dry conditions. On Monday, a relatively moist northwest flow could result in isolated to scattered snow showers mainly over the northwest/northern mountains. Some of this activity could spill into the adjacent foothills across the north. The longwave ridge is then expected to expand east, and encompass much of the Rockies by Tuesday. This longwave ridge is expected to remain over the area through the end of the week. However disturbances moving through the mean longwave ridge could result in some mountain snow showers at times. Models show the strongest of these disturbances impacting the area on Thursday. 00Z models show this wave briefly flattening out the upper ridge with a decent shot of precipitation over the west, possibly spilling east of the Divide with a Pacific cold front late Thursday into Thursday night. Have elected to keep PoPs on the low side for this wave Thursday since 1) the wave will be moving into a mean ridge, and 2) models have had various timing/strength of this feature over the past couple of days. Temperatures through the extended are expected to be 5 to 15 degrees above average. Due to the persistent above average temperatures, snowmelt is expected over the western valleys. However the rate of snowmelt will be tempered by overnight lows dipping below freezing or at least to there frost point, and winds look to be fairly light. Thus not expecting any major issues at this time. && .AVIATION.../12Z ISSUANCE/ WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES A moist westerly flow with a couple of embedded disturbances will keep numerous valley rain and mountain snow showers vicinity and north of a KAFO-KPNA line through Friday afternoon. Snow levels will remain near 8000 feet with MVFR conditions in mainly -RA expected to prevail at KJAC through Friday morning. A cold front will push NW-SE across the area late Friday afternoon, early Saturday evening spreading some MVFR rain and snow showers southward to the Interstate 80 corridor, vcnty KRKS. Drier air and some clearing will prevail from NW-SE 06z-12z Saturday leaving patchy fog or local LIFR/IFR ceilings partially obscuring terrain. EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES A stationary front extended along a vicinity KRIW-KCPR line early this morning with areas of MVFR cigs, local IFR/LIFR cigs to the north of the front. This front will gradually retreat north and eastward through the morning with ceilings lifting/dissipating; VFR conditions prevailing by 15z. The cold front will then make a southward push Friday afternoon, back to a vicinity KRIW-KCPR line by 02z Saturday. Areas of MVFR/local IFR ceilings with scattered rain showers, snow showers above 8000 feet with frequent mountain obscurations will follow the cold front. Drier air and clearing skies will prevail NW-SE 06z-12z Saturday leaving patchy fog or local IFR/LIFR ceilings partially obscuring terrain. && .FIRE WEATHER... Fire Danger low across most of the forecast area through the weekend as continued good existing snow cover or precipitation and relatively high minimum RH values combine with continued seasonal to below seasonal temperatures. Best chances for measurable precipitation will occur west of the Divide mainly over the mountains...with isolated chances east of the Divide tonight and again Sunday. Gusty west to southwest winds can be expected to continue across much of the region through the weekend. Smoke dispersion will be fair to very good across most of the forecast area each afternoon through at least Sunday. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 PM MST this afternoon for WYZ002- 013-014-023-024. Winter Storm Warning until 5 PM MST this afternoon for WYZ001- 012. && SHORT TERM...Braun LONG TERM...WM AVIATION...AEM FIRE WEATHER...Braun
Hazardous Weather Outlook National Weather Service Riverton WY 233 AM MST Fri Mar 10 2017 WYZ001>020-022>030-111300- 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- 233 AM MST Fri Mar 10 2017 ...Winter Storm Warnings and Winter Weather Advisories across the west today... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Snow and occasionally strong wind will continue today across the western mountains, with heavy possible snowfall this morning...tapering off this afternoon. Western valleys will see rain or a rain, snow mixture again today. Please see the winter weather warnings and advisories for more details. Also patchy, morning valley fog could also occur. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Saturday night through Sunday night...The next storm system will bring a quick shot of moderate snow and strong gusty wind to the western mountains through Sunday morning before shifting east of the Divide Sunday afternoon and evening with chances for very blustery scattered rain or snow showers. .SPOTTER INFORMATION STATEMENT... Spotters are requested to report snowfall amounts.
Special Weather Statement National Weather Service Riverton WY 633 AM MST Fri Mar 10 2017 WYZ017-018-101600- Wind River Basin-Lander Foothills- Including the cities of Riverton, Shoshoni, and Lander 633 AM MST Fri Mar 10 2017 Areas of fog will be encountered across the Wind River Basin until around 9 AM. Visibility in the fog will be under a quarter mile in spots. In addition, temperatures will be below freezing which could result in fog depositing some ice on exposed surfaces. Motorists are urged to slow down, use low beams when fog is encountered, and be aware some black ice could be present on area roadways. 21
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The emergency manager reported flooding along the Blacks Fork River near Granger and Little American. A mobile home park along the river was evacuated for 2 days but little or no damage was reported.
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, March 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: 681418.