Scattered showers and thunderstorms developed across Sweetwater County well ahead of an upper-level low in the Pacific Northwest. Several storms strengthened over the moderately elevated terrain in the south-central portion of the county.
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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.
Scattered showers and thunderstorms developed across Sweetwater County well ahead of an upper-level low in the Pacific Northwest. Several storms strengthened over the moderately elevated terrain in the south-central portion of the county. One storm produced a short-lived, rope funnel cloud that was photographed from the north.
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 Oct 1, 10:07 AM MST, 4 hours 3 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1107 AM MDT SAT OCT 1 2016 .SHORT TERM...TODAY THROUGH MONDAY NIGHT The last of this evenings convection has cleared the area and dissipated over southern Montana. Currently, the nearest area of convection is a thunderstorm cluster moving north across central Idaho within a stream of moisture rounding the base of the next upstream low off the Pacific Northwest coast. These cells appear to be related to the first vort lobe that will track northeast across Idaho and western Montana ahead of the main low with another vort lobe taking the same track this afternoon, all within the broad circulation around this closed low. This second vort lobe that will brush our far western zones as well, as marginal instability and southwest difluent flow will result in a good chance of afternoon and evening showers and thunderstorms in western Wyoming later today. As this low moves inland across Oregon and northern California Sunday, the southwest steering flow will increase along with increasing instability resulting in an increase in thunderstorm activity across the west half of the cwa by sunday afternoon. Then on Sunday night, the mid and upper level low will track to Idaho/Nevada/Utah with Wyoming underneath an increasingly strong southern difluent flow ushering in more moisture. This will likely result in another round of a rapid succession of thunderstorms moving south to north across the area Sunday night in the same fashion as two Thursday nights ago, but with with not quite as much rainfall. The NAM/GFS/EURO all seemed to have come to a general consensus as to tracking this low northeast across northwest Wyoming by Monday. This will mean that sfc temperatures will not be as cool as originally anticipated on Monday during the time all the dynamics of this storm system come together. Widespread rainfall can be expected Monday, especially over the north and west, closer to the track of the low. With the left front quad of the jet ovhd as well as q vector forcing, especially closer to the track of the low, plenty of measurable rainfall on the order of one half inch to one and a quarter inches could fall across the northwest third of the CWA Sunday afternoon and night, Monday, and Monday night. Snow levels will drop to around 8500 feet Monday to 7500 feet late Monday night as colder air aloft streams in from the west southwest. High temperatures Monday should be 10 to 15 degrees cooler on Monday in most areas. As the almost vertically stacked low pulls out into eastern Montana, wrap around moisture will continue the rain and snow shower activity closer to 12z Tuesday. The 700mb low will be a bit too far north for classic rain and snow banding off the favored mountain areas across the north half of Wyoming, in spit of the weak instability and moisture around. By 12z Tuesday, have painted the Big Horn Mountains, extreme northern Absaroka and highest Wind River Mtns with around 4 inches of total snow during this precip event, but that is still a long ways off so plenty of time to adjust. South southwest winds should increase to 35 to 45 mph from KRKS to KCPR and 25 to 35 mph across the Wind River and Big Horn Basins as well as Johnson County and the Big Horn Mountains, south and east of the storm center where 700mb winds are progged to blow at 50 knots. .LONG TERM...TUESDAY THROUGH SATURDAY 00Z guidance suite in good agreement with a stacked low over eastern Montana at 12Z Tuesday. This low is expected to slowly push northeast into south-central Canada late Tuesday/Tuesday night. Breezy to windy conditions are expected Tuesday along with isolated to scattered mountain snow/valley rain and snow showers with an emphasis across the northwest and north. Snow levels looks to be around 6500 feet. The forecast area remains on the cyclonic side of the upper jet through Thursday. This combined with enough moisture and instability for a slight chance of some diurnal valley rain/mountain snow showers becoming enhanced at times by some perturbations in the flow. Thursday night and Friday look to be mainly dry as some ridging takes hold of the area. This looks to be short-lived as a low amplitude trough is projected to track east across the Northern Rockies Friday night/Saturday time frame. For now the bulk of the moisture and precipitation is expected to be north of the area. Temperatures are expected to be below average, but nothing extreme Tuesday through Thursday with more seasonal temperatures Friday and Saturday. && .AVIATION.../18Z ISSUANCE/ West of the Continental Divide...KJAC/KBPI/KPNA/KRKS VFR conditions to prevail for most terminal sites except KJAC later tonight. Patchy low clouds will occur in the far west mountain/valleys until 19Z. Otherwise...scattered showers and thunderstorms will develop after 18Z and continue through 02Z...followed by another area of scattered showers after 04Z spurred on by an upper level disturbance. Local MVFR/brief IFR conditions may occur with these showers/storms...especially over/near KJAC from 04Z to 08Z. Low level wind shear will also be prevalent for a short period after 14z at/near the kjac terminal. East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL VFR conditions to prevail through the forecast period. Isolated showers or a thunderstorm will occur after 21Z through 06Z Sunday and then again after 09Z Sunday over/near kCOD. KLND will see VCNTY showers/thunder between 21Z this afternoon and 01Z this evening. && .FIRE WEATHER... A large Pacific low pressure trough off of the Pacific Northwest coast will move inland and eventually across western and central Wyoming through Wednesday bringing increased clouds and showers with isolated afternoon and evening thunderstorms. Temperatures will cool through Wednesday with the onset of more widespread precipitation Monday and Monday night...snow levels will lower to around 7500 feet at night rising to around 8500 feet on Tuesday. Precipitation amounts could become quite significant... especially in the north and west mountains. && .RIW Watches/Warnings/Advisories...None. && SHORT TERM...Lipson LONG TERM...WM AVIATION...AR FIRE WEATHER...Lipson
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 552 AM MDT SAT OCT 1 2016 WYZ001>020-022>030-021200- 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- 552 AM MDT SAT OCT 1 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT AREAS OF FOG ACROSS THE FAR WESTERN VALLEYS THIS MORNING. ISOLATED AFTERNOON AND EVENING THUNDERSTORMS...MAINLY IN WESTERN WYOMING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SUNDAY...SCATTERED SHOWERS AND ISOLATED AFTERNOON AND EVENING THUNDERSTORMS IN WESTERN WYOMING WITH ISOLATED SHOWERS AND THUNDERSTORMS EAST OF THE DIVIDE. MONDAY AND TUESDAY...TURNING MUCH COOLER WITH A GOOD CHANCE OF SHOWERS...MOUNTAIN SNOW AND ISOLATED THUNDERSTORMS. SOUTHWESTERLY 30 TO 40 MPH WINDS FROM ROCK SPRINGS TO CASPER MONDAY. .SPOTTER INFORMATION STATEMENT...SPOTTERS ARE ENCOURAGED TO REPORT HAIL SIZE AND WIND SPEEDS OVER 45 MPH WITH ANY THUNDERSTORMS THANK YOU.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1253 PM MDT SAT OCT 1 2016 WYZ001-012-013-023>029-012200- YELLOWSTONE NATIONAL PARK-TETON AND GROS VENTRE MOUNTAINS- JACKSON HOLE-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- INCLUDING THE CITIES OF...LAKE...MAMMOTH...OLD FAITHFUL... JACKSON...AFTON...ALPINE...STAR VALLEY RANCH...THAYNE... PINEDALE...LA BARGE...BIG PINEY...FARSON...KEMMERER...COKEVILLE... ROCK SPRINGS...GREEN RIVER 1253 PM MDT SAT OCT 1 2016 THROUGH 4 PM...SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP ACROSS WESTERN WYOMING...MOVING TO THE NORTHEAST AT AROUND 25 MPH. THE MAIN THREAT FROM THIS ACTIVITY WILL BE BRIEF HEAVY RAIN...GUSTY WINDS 20 TO 30 MPH AND OCCASIONAL LIGHTNING.
The Riverton/Lander radar (KRIW), 177 km away, was scanning. The volume nearest the first event began at 21:10 UTC.
1 funnel cloud. Local standard time, as filed.
A rope funnel cloud was photographed over the higher terrain near Table Rock south of Interstate 80.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2016Every state in 2016This day in weather historyWarnings in Wyoming, October 2016
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: 659809.