A big push of monsoon moisture led to five days of scattered thunderstorms over the Mojave Desert and the Sierra. Many storms produced flash flooding and/or high winds.
Every event with a place to put it. Tap one for its entry below.
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.
A big push of monsoon moisture led to five days of scattered thunderstorms over the Mojave Desert and the Sierra. Many storms produced flash flooding and/or high winds.
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 Jul 17, 11:36 AM PST, 4 hours 24 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 1236 PM PDT Sat Jul 17 2021 .SYNOPSIS...Thunderstorms will be on the increase across northwest Arizona this afternoon with showers and thunderstorms spreading into southern Nevada and southeast California tonight and Sunday. There will be a chance of showers and thunderstorms through the week. With the higher humidity levels temperatures are expected to be around normal. && .SHORT TERM...Tonight through Monday Night Thunderstorm activity beginning to show up in western Yavapai County early this afternoon. This activity is likely to spread west into eastern Mohave County later this afternoon. These storms are of the typical variety for a moist day in the Monsoon. The main threats from these storms will be wind and flash flooding should any of them become intense enough to cause issues. Of more importance is the upper level short wave moving through the area this evening and tonight. It will come right out of southern Arizona and track across the southern part of the CWA and eventually up into central Nevada and eastern Sierra as it rotates around the upper level high pressure to the east. The main concern is thunderstorm activity associated with this wave. It may end up generating thunderstorms all through the night tonight as it transits the area. At this time we don't anticipate any major weather impact concerns from these storms after midnight of so. The loss of daytime heating and lower level instability will limit storm intensity. Until midnight though, storms will need to be watched as they have the potential to produce damaging wind gusts. Of secondary concern is flash flooding where storms tend to stall or back build. With higher moisture moving in on the heels of the short wave mentioned above, expect that Sunday will be an active day for thunderstorms. With little in the way of steering flow, we are looking as pulse type convection that will generate a flash flooding threat. As a result WPC has place most of the area in Marginal risk for excessive rainfall. One exception of course is the eastern Sierra where dry thunderstorms area expected. More on that in the Fire Weather section below. Still no defined feature evident on the models for Monday but guidance does indicate that monsoon moisture will be well entrenched into Lincoln, Clark, Mohave and all but far northwest San Bernardino County Monday for isolated to scattered showers and thunderstorms. .LONG TERM...Tuesday through Friday. High pressure is forecast to set up east of the area in the long term, setting up a progressively favorable monsoonal flow into our area. On Tuesday, storms will be favored primarily in Mohave County with isolated convection mainly over the mountains across parts of the Mojave Desert and southern Great Basin. Mohave County continues to be the favored area for storm development on Wednesday however, higher precipitable water values spread westward resulting in better chances further west. The higher moisture is entrenched across our eastern zones on Thursday and Friday with scattered to numerous storms over the eastern half of the area and isolated to scattered storms over the western half. With the daily storm activity, expect plenty of cloud cover at times which will impact temperatures to some degree but will also determine when and where thunderstorms develop each day. Flash flooding is the primary concern from this expected increase in available moisture and whether the flooding concerns are localized or more widespread will depend on other factors such as lifting mechanisms which are currently unforecast and unknown. && .FIRE WEATHER...The Fire Weather Watch over the southern Sierra has been upgraded to a Red Flag Warning. Thunderstorm activity moving into the area early Sunday will bring the threat of lightning to a dry lower atmosphere. Given the precarious state of fuels in the Sierra this will create the potential for lighting to start fires in an environment where rapid spread is possible. Luckily, the atmosphere moistens up relatively quickly. By Monday morning, the threat of dry thunderstorms diminishes to the point where a Red Flag Warning is no longer needed. It should be noted though that thunderstorms remain in the forecast through the period and have the potential to start wildland fires all through the week. && .AVIATION...For McCarran...Wind direction today has been variable out of the south. Both ASOS and Midfield wind sensors show the winds varying between 220-150. Speeds have generally been under 10kts with some gust in the 15-18kt range. There is really no strong weather mechanism driving the winds today. It is likely we see this variability in direction for the rest of the evening. There is still a potential outflow winds from storms in Arizona to reach the terminal later this evening, likely around the 02-04Z time frame. Confidence is low until actual storms form over AZ this afternoon. For the rest of southern Nevada, northwest Arizona and southeast California...Generally quiet weather conditions are expected through the TAF period. However, after 00Z, outflow winds from Arizona are expected to push westward and could impact several TAF sites. KIFP/KEED have the best chance of seeing outflow winds shift directions to the east and depending on the strength when they arrive, also bring some blowing dust. That being said, confidence in BLDU and wind speeds are currently low. There is a lesser chance that these outflow winds make it to the LV Valley but included this potential in the TAFs, && Short Term/Fire Weather...Lericos Aviation...Lericos/TB3 Long Term...Salmen For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter
The Las Vegas radar (KESX), 142 km away, was scanning. The volume nearest the first event began at 00:00 UTC.
5 flash flood, 2 thunderstorm wind. Local standard time, as filed.
A man drowned on the California side of Lake Havasu. Thunderstorm winds gusting to 46 mph contributed to the drowning.
Main Street was flooded with water and debris.
Half an inch of rain in 15 minutes caused flooding of Dogwood Street between Minneola Road and Spyrock Avenue.
Water, rocks, and mud flooded the intersection of Old Fort Irwin Road and Old Highway 58.
Flash flooding caused mud and rock slides along Highway 168 near Aspendell, blocking the road and causing several vehicles to be stuck.
Lillyhill Drive was flooded six to eight inches deep near Bailey Avenue.
Thunderstorm winds blew down six power poles. Multiple vehicles were stuck.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Thunderstorm Wind, San Bernardino | 2021-07-17 | 58 | Male | In Water | Indirect |
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, July 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: 975361, 975416, 975417, 975420, 975421, 975422, 975424.