High based showers developed over the Wind River Mountains and drifted toward the Lander foothills. Some of these showers collapsed over Lander and produced strong wind gusts.
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The episode as NWS RIW wrote it up.
High based showers developed over the Wind River Mountains and drifted toward the Lander foothills. Some of these showers collapsed over Lander and produced strong wind gusts. At the Lander airport, a wind gust of 64 mph was measured.
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 17, 10:10 AM MST, 2 hours 9 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1110 AM MDT Mon Jul 17 2017 .SHORT TERM...Monday through Wednesday night Issued at 225 AM MDT Mon Jul 17 2017 As for the weather today, it will be described in four words. And those words are, more of the same. The radar is quiet right now. However, more showers and thunderstorms are on the way. In the morning, a weak system will pass across southern Wyoming and may bring a few showers this morning. However, the main event will be this afternoon as second, more potent shortwave approaches the region. All areas will have a chance of at least an isolated thunderstorm with the best chance across northern areas. The stronger storms would more than likely be across the north as well with the best shear and forcing. One difference is that this should be a later show as the atmosphere may need more time to reload. The NAM, which has been doing the best job lately with the convection, shows a complex developing across the western mountains and then moving across the north through well after midnight. We adjusted POPS tonight to show this as well. And again, for around the tenth day in a row or something, I don't know it's been so many I've lost count, the main threat will be strong outflow winds. These will move out by sunrise Tuesday. As for high temperatures, the GFS has been more reliable than the NAM so we kept temperatures warmer, although a few degrees cooler than recent days. With rising heights and temperatures aloft for Tuesday, along with a drier air mass moving in, Tuesday looks drier. Actually, it looks dry for almost everyone. The NAM is dry and even the GFS has trended away from it's constant thinking the Absarokas and Bighorn Ranges are wetter than the Olympic Mountains in western Washington. As a result, we have removed POPS from all areas and went completely dry. With more sunshine and higher thicknesses, temperatures will once again begin to warm with 80s and 90s widespread across the lower elevations. On Wednesday, we see may see the beginning of the arrival of a seasonal friend. That friend is the monsoon with some moisture starting to creep in from the south as the ridge axis shifts to the east. For now, we kept the convection mainly across the south but this may need to be adjusted with time. As for temperatures, what a surprise, in keeping with recent days, temperatures should be above normal for most locations once again. .LONG TERM...Thursday through Monday Issued at 225 AM MDT Mon Jul 17 2017 The GFS and ECMWF models have a decent weather disturbance moving around the western periphery of the upper high on Thursday into late Thursday night. Provided the cloud shield associated with this weather system is not too thick, a better chance of showers and thunderstorms would occur. Far northern WY would be on the fringe of this activity per the models. Storms would produce locally heavy rain in places, but as with any given summer day, not everyone will see rain. High temps Thurs would be slightly cooler most areas. In the southern zones, the cooling will be more noticeable due to the expected cloud cover and made adjustments to reflect this thinking. Friday looks mainly dry with isolated thunderstorms in the far south. Very warm to hot high temps. The GFS model Saturday has a weather system dropping into Montana and then this system passes across WY on Sunday. It has a cool front with it and generates some showers and storms Saturday night into early Sunday in the northeast and east zones. The ECMWF model is farther northeast with this feature. Thus, much less impact on the area and less cooling. Have went with isolated showers and storms Saturday night from Buffalo to Casper and dry elsewhere. Behind this system on Sunday, conditions look to be dry. Have cooled high temps a few degrees east of the divide for Saturday with little change in the west and southwest. High temps Sunday will be similar to Saturday and possibly a few degrees warmer in places. Next Monday looks dry with very isolated thunderstorms over the mountains. Temps will be very warm to hot once again. && .AVIATION...18Z Issuance VFR conditions will prevail through the forecast period. Isolated to widely scattered showers, with possibly a thunderstorm or two, continue across the southwest, vicinity KRKS-KBPI-KPNA, and have now moved toward KLND-KRIW. An upper level disturbance will bring a round of widely scattered showers and thunderstorms across the area this afternoon and expected to exit the area by midnight, or primarily from 22z Mon-06z Tue. A few storms could be marginally severe with wind gusts 40-50 knots and hail. The strongest storms are expected vicinity and north of a KJAC- KWRL- KCPR line. Some lingering showers will be possible vicinity KRKS-KCPR between 06z-09z Tuesday. && .FIRE WEATHER... Issued at 225 AM MDT Mon Jul 17 2017 Expect another warm day today although a few degrees cooler than over the weekend in many locations. A couple of upper level disturbances will move across the state from the west and bring another round of isolated to widely scattered showers and thunderstorms to the area. And again, the main threat will be strong outflow wind gusts. Thunderstorms will be mainly later in the day and could last through the night across portions of the northern zones. Relative humidity will fall into the teens for many of the lower elevations. However, wind should remain below critical levels outside of any shower or thunderstorm. Mixing and smoke dispersal will range from fair to good in the Basins East of the Divide to excellent in the western mountains. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Hattings LONG TERM...AR AVIATION...LaVoie FIRE WEATHER...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 230 AM MDT Mon Jul 17 2017 WYZ001>020-022>030-181100- 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- 230 AM MDT Mon Jul 17 2017 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Isolated to widely scattered afternoon and evening thunderstorms. Strong thunderstorms are possible in northern Wyoming. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Wednesday through Thursday...Isolated to widely scattered afternoon and evening thunderstorms mainly over the mountains and adjacent foothills. The main hazard will be occasional strong gusty winds. Stronger storms will likely produce locally heavy rain. Friday...Isolated afternoon and evening thunderstorms over the south and southwest. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report wind gusts over 45 mph. Thank you.
The Riverton/Lander radar (KRIW), 34 km away, was scanning. The volume nearest the first event began at 19:19 UTC.
1 thunderstorm wind. Local standard time, as filed.
A wind gust of 64 mph from a collapsing shower was measured at the ASOS at the Lander airport.
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: 705678.