A push of monsoon moisture fueled thunderstorm development over the Mojave Desert. Isolated severe weather and flash flooding occurred.
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 push of monsoon moisture fueled thunderstorm development over the Mojave Desert. Isolated severe weather and flash flooding occurred.
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 22, 11:49 AM PST, 55 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 1249 PM PDT Sat Aug 22 2020 .SYNOPSIS...Moisture surging into the area will bring the threat of afternoon thunderstorms through Monday, mainly over higher terrain, before drier air starts working in from the southwest Tuesday. Temperatures will remain several degrees above late August averages, except in spots where thunderstorms occur early in the afternoons. && .SHORT TERM...through Sunday Night. As of noon, waiting for convective initiation. Early morning debris clouds have mostly dissipated, and thin mid and high level clouds which have developed roughly from Las Vegas northward are not likely to slow down daytime heating very much, although the thick smoke and haze blanketing much of the area could also be a factor. Cumulus were popping over the Spring Mountains and Sheep Range, but not over the McCullough Range as of this typing. Mesoanalysis showed CAPE of 1500-2500 J/kg in an axis from the Morongo Basin to near Mesquite, with over 1000 J/kg of downdraft CAPE. Minimal shear was in place, and PWs of 1 to 1.75 inches were in the same area, so the main threats are likely to be brief downpours and strong outflow winds, some of which may trigger new cells. For Sunday, CAM output shows the most favored area for storms shifting further north and east, roughly along and east of an arc from the NNSS to Primm to Wikieup. This will likely be modulated somewhat by exact thunderstorm location and coverage today. Another concern will be dry lightning on the northern fringes of the moisture tongue. Will forgo any Fire Weather products at this time due to expecting a mix of wet and dry storms, with less than 15% coverage of dry storms. That being said, fuels are extremely dry, and what happens today will help inform our decision tonight on whether to issue for tomorrow. .LONG TERM...Monday through Friday. The overall setup in the weather pattern for the first half of next week won't vary much day to day with high pressure centered near the Four Corners and PWATs around 1 inch sitting south and east of I-15. Afternoon convection will be possible Monday and Tuesday, though small details will drive storm chances outside of higher terrain. However, by Wednesday, southwest flow will push into the region ahead of a shortwave over central California which will usher in drier air, shoving the better moisture back into southern Arizona. Therefore, precipitation potential will decrease midweek. Low confidence in the forecast for the second half of the week as models disagree on how much dry air will move in and how long it will stay in place over the region. Some models have a brief break in monsoonal moisture while others have a significant push of dry air that holds tight going into next weekend. This will play a significant role for the second half of next week-will it be hot and dry or will monsoon moisture make a come back? Stay Tuned! && .AVIATION...For McCarran...Potentially significant impacts are possible this afternoon in the Las Vegas Valley. Generally light winds favoring an easterly direction through 20z before thunderstorms develop south & southwest of the valley by 21-22z. Possible impacts include visibility reductions due to heavy rain and winds gusting to 35 kts or greater from various directions. Approaches will be complicated by TSRA development surrounding the Las Vegas Valley. PIREP solicitation will be highly recommended. These impacts should cease by the 01-03Z time frame, returning to light winds and minimal impacts through the rest of the TAF period. For the rest of southern Nevada, northwest Arizona and southeast California...TSRA development this afternoon could impact terminals at KVGT/KHND as well as KDAG. Lower confidence in impacts to KBIH/KIFP and KEED. Most likely impact will be strong outflow winds generated by TSRA vs a direct TSRA impact. Gusty winds over 35 kts will be possible for these terminals during the 20-01Z time frame. This activity should subside after 01Z tonight returning all sites to VFR and light winds. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && Short Term...Morgan Long Term...Nickerson Aviation...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), 67 km away, was scanning. The volume nearest the first event began at 20:47 UTC.
3 flash flood, 1 hail. Local standard time, as filed.
Water, mud, and boulders were on Interstate 15.
Hail up to golf ball size accumulated several inches deep on Interstate 15 at Mountain Pass. Vehicle damage was reported, including broken windshields.
Nipton Road was flooded.
Several inches of water flooded Cima Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2020Every state in 2020This day in weather historyWarnings in California, August 2020
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: 911557, 911559, 911560, 911561.