Thunderstorms developed to the west of Casper on July 9th. A wind gust of 60 mph was reported at the Casper airport.
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The episode as NWS RIW wrote it up.
Thunderstorms developed to the west of Casper on July 9th. A wind gust of 60 mph was reported at the Casper airport.
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 Jul 9, 10:21 AM MST, 2 hours 1 minute earlier.
Area Forecast Discussion National Weather Service Riverton WY 1121 AM MDT Sun Jul 9 2017 .SHORT TERM...Sunday through Tuesday night After some decrease in coverage in thunderstorms, things look to ramp up a bit across the area for the next couple of days. As a of now, things are quiet and this should hold through most of the morning. However, with ridge axis moving away from the area, heights will fall and with another shortwave moving through the flow around the base of the ridge, we will likely have another round of showers and thunderstorms. And once again, it seems like I have written this a thousand times over the past few weeks, the main threat will be strong winds gusts given the, all together now, inverted V soundings and large dew point depressions. And, yes, this also includes the little green blob showers as well. As for temperatures, look for another hot day. We are following the GFS more closely since the NAM guidance looks to be drunk once again and looks too low, like a couple of previous days. Activity may linger a bit past midnight tonight as well. As of now, the main event looks to be on Monday. A more potent shortwave will approach the area on Monday. The soundings are also showing some decent mid level winds and some direction and speed shear. This is especially so across northern Wyoming where the best upper level forcing will be. The best jet dynamics will likely remain over Montana, but will be close enough that there could be severe thunderstorms. The Storm Prediction Center has placed far northern areas under a slight risk with the rest of the area under a marginal risk. Once again, the main threat will be, wait for it, damaging wind gusts. However, with the chance of tilted updrafts in the storms there could also be some large hail, especially further north. Not enough confidence to put severe wording in the forecast, but it will have to be watched. Again, we went with the warmer guidance with high temperatures into the 90s once again in the lower elevations. By Tuesday, it should be quieter. Some drier air will move back into the state along with surface high pressure. As a result, this should be a mainly dry day across the state. The GFS is still doing it's thing in overdoing convection across the mountains though. For now, we left slight POPS in across the mountains but future shifts may want to go with a dry forecast if the trends continue. Temperatures will remain above normal once again. .LONG TERM...Wednesday through Sunday Global models show a strong subtropical ridge building back into the Rockies in the extended. Wednesday and Thursday the high is elongated from west to east across the southern CONUS, but by Friday into next weekend 00Z models are showing the ridge becoming centered in the Utah area. Disturbances rotating through the ridge with daytime heating will keep isolated to perhaps locally scattered diurnal convection each day mainly over the mountains and adjacent foothills. There will be day to day variability, but hard to pin point this far out. Precipitable water values generally range between 0.5 and 0.75 each day, keeping the monsoonal moisture south of the forecast area now. Temperatures are expected to be 5 to 10 degrees above average through the extended. && .AVIATION...18Z Issuance VFR conditions to prevail through the period. Showers and thunderstorms will be more widespread this afternoon and evening, with the initial activity along a KCOD-KRIW-KLND line. As these showers and thunderstorms move eastward through 22Z, additional convection will develop across northern and southern portions. Storms will transition to showers after 03Z and become widespread across northern and central portions through 08Z Monday. Isolated showers will be possible near KRKS-KBPI-KPNA during this time. Outflow wind gusts of 30 to 40 knots will continue to be the main threat, along with locally heavy rain possible with some storms. Local MVFR visibilities can be expected in these areas of heavy rain. Mountains may be obscured at times, especially from 06Z-18Z Monday west of the Divide, as additional clouds and possible showers move in during this time. && .FIRE WEATHER... After a quieter day, expect an increase in coverage of showers and thunderstorms for through Monday. Temperatures will remain above normal for just about all locations. Relative humidity will fall below 15 percent at times Sunday and Monday across portions of southern Wyoming and the basins East of the Divide. However, wind will remain light to moderate today. There could be a bit more wind on Monday across western Wyoming on Monday. Strong and erratic wind gusts will be possible with any shower or thunderstorm the next couple of afternoons and evenings. Most thunderstorms should have less than a tenth of an inch or rain. Mixing and smoke dispersal will range from fir to good in the basins to good to excellent in the mountains and normally breezier areas. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Hattings LONG TERM...Murrell AVIATION...LaVoie FIRE WEATHER...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 137 AM MDT Sun Jul 9 2017 WYZ001>020-022>030-101200- 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- 137 AM MDT Sun Jul 9 2017 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Isolated thunderstorms this afternoon and evening. Any storm can have strong outflow winds. The strongest storms will be across the northern zones. .DAYS TWO THROUGH SEVEN...Monday through Saturday Monday...Isolated to widely scattered afternoon and evening thunderstorms. Gusty outflow wind will be common near any activity. Strong to severe thunderstorms are possible across northern Wyoming. Wednesday through Saturday...Isolated afternoon and evening thunderstorms mainly over the mountains and adjacent foothills. The main hazard will be strong, gusty winds. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report wind gusts over 45 mph and any size hail. Thank you. Team Riverton
The Riverton/Lander radar (KRIW), 164 km away, was scanning. The volume nearest the first event began at 19:21 UTC.
1 thunderstorm wind. Local standard time, as filed.
The ASOS at the Natrona County airport reported a wind gust of 60 mph.
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, July 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: 705677.