Monsoon moisture fueled thunderstorms over the Mojave Desert, many of which produced severe winds and flash flooding.
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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 VEF wrote it up.
Monsoon moisture fueled thunderstorms over the Mojave Desert, many of which produced severe winds and flash flooding.
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 Las Vegas, NV wrote its last area forecast discussion before the first event at Aug 9, 1:28 PM PST, 1 hour 13 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 228 PM PDT Mon Aug 9 2021 .SYNOPSIS...Thunderstorm chances will increase in areas southeast of Interstate 15 Tuesday and spread to much of the region Wednesday. After a lull late in the week, thunderstorm chances are expected to ramp up again over the weekend and into early next week. The main impacts for the upcoming active period will be flash flooding, especially in the higher terrain, and gusty outflow winds. && .SHORT TERM...through Wednesday night. The latest moisture push is making its presence known early this afternoon. Satellite loop showed scattered flat cumulus southeast of I-15, with spotty deep convection noted over the Hualapai Mountains and south of Twentynine Palms. Surface obs showed a well defined moisture boundary, with dewpoints in the 50s and lower 60s from Twentynine Palms to Boulder City and southeastward, but only in the 20s and 30s from Barstow to Las Vegas and northwestward. Much of the smoke and haze had cleared out, with visibility restrictions only noted in the Owens Valley and near Tonopah. The main forecast concern will be increasing thunderstorm chances and impacts. Mid level water vapor loop showed the wave which had been noted by previous shifts near Ensenada and drifting north, with a well defined comma tail of lift across extreme southern California into Arizona. As this feature continues its northward drift, it will push moisture and lift farther north into our CWA, resulting in increasing thunderstorm chances tomorrow and Wednesday. Impacts will include outflow boundaries causing suddenly shifting and gusty winds, lightning outside the rain cores potentially causing new fires, and very heavy rain. Toyed with the idea of a Flash Flood Watch for Mohave County, but eventually decided against it because the flooding threat, while not absent, is likely to be isolated rather than widespread. Similarly, there is a nonzero risk of flooding for the Morongo Basin, Death Valley, and Mojave National Preserve areas. If future guidance suggests flooding potential to be more widespread, Watches may be needed. Temperatures tomorrow and Wednesday will come down a few degrees over the Mojave Desert due to the increasing moisture/clouds/storm chances, with little change expected over the southern Great Basin. .LONG TERM...Thursday through Monday. The monsoonal moisture that returns the first half of this week will linger over the region through next weekend and early next week. The latest ensemble-based NBM continues to indicate a slight waning in thunderstorm potential Thursday and Friday as a general southeast flow remains over the region but no large scale trigger for convection aside from surface heating. Thus, chances of thunderstorms will largely be confined to Mohave County Arizona and the higher mountains of southern Nevada and southeast California. It appears thunderstorms will become more active going into the weekend. The NBM PoP values increase over much of northwest Arizona, southern Nevada and eastern San Bernardino County Saturday and Sunday. This is in response to the approach of a large inverted trough lifting up from northern Mexico which is depicted by the ECMWF and GFS ensembles, as well as the operational deterministic models. This will be the main feature to watch going into next weekend bringing the potential for additional deep moisture up ahead of it into our region. This may still be a player into Monday, and NBM PoP values of 25-55 percent remain over the aforementioned areas. && .AVIATION...For McCarran...South-southwest winds will continue through the evening and overnight with gusts diminishing after sunset. Light and variable winds early Tuesday morning should give way to east-southeast components around 10 knots after 16Z and continuing through the afternoon and possibly the evening. There is a slight possibility that distant thunderstorms in the Peach Springs corridor Tuesday evening could produce strong enough winds to reach the terminal area though confidence is too low to mention in the TAF. For the rest of southern Nevada, northwest Arizona and southeast California...South-southwest winds will continue across most of the region with gusts of 20-30 knots diminishing after sunset. Diffuse haze and smoke around northern Inyo County and central Nevada should not drop visibility below VFR conditions. Isolated thunderstorms near Twentynine Palms and near Kingman will dissipate this evening. Thunderstorm coverage will increase Tuesday afternoon across northwest Arizona and the Colorado River Valley from IFP to HII along with the potential for widespread strong outflow those storms late Tuesday afternoon and evening. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && SHORT TERM...Morgan LONG TERM...Adair AVIATION...Adair For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter
The Santa Ana Mts radar (KSOX), 163 km away, was scanning. The volume nearest the first event began at 22:42 UTC.
3 thunderstorm wind, 1 flash flood. Local standard time, as filed.
Highway 62 near mile marker 42 was flooded with two feet of flowing water and large debris.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, August 2021
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: 981258, 981259, 981273, 981275.