High pressure building in from the east brought five days of excessive heat to much of the Mojave Desert.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
High pressure building in from the east brought five days of excessive heat to much of the Mojave Desert.
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 26, 9:55 AM MST, 1 hour 5 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 955 AM PDT Thu Aug 26 2021 .SYNOPSIS...Hot and dry conditions will continue through the weekend across most of the area although monsoon moisture creeping in from the south is expected to limit the extent of afternoon heating in our southern areas and could bring a few isolated showers and thunderstorms to Mohave County on Sunday. During the early to middle part of next week, shower and thunderstorm coverage expands west and north to include eastern and southern San Bernardino County and Clark, Lincoln, and Mohave counties. && .UPDATE...Multitude of wildfires across California will continue to create areas of dense smoke/haze/lower visibility's across Inyo and Esmeralda Counties. The visibility at Bishop has dropped to 4 miles over the past few hours. Elsewhere, hazy conditions will persist. Narrow axis of mid-level moisture that got pulled inland between the Great Basin trough and southern Plains high is draped across San Bernardino and southern Mohave Counties this morning. Convective allowing models show any convection will develop/stay east of Mohave County today. Models suggest drier intrusion of air associated with Great Basin trough will keep the threat of thunderstorms on Friday to areas from Flagstaff east. No update necessary this morning. && .DISCUSSION...Today through Wednesday. We are keeping an eye on what could be a transitional change from hot and dry conditions area wide through the weekend along with a low grade monsoon moisture surge across our southern areas over the weekend. There is some potential, but a great deal of uncertainty, regarding a more substantial moisture surge featuring tropical characteristics next week. Details of this potential surge is explained quite well in the section marked [Tropical] below. Focusing on heat related concerns in the near term, a somewhat marginal heat event, both in terms of coverage and duration, will get underway today. An Excessive Heat Warning is in effect for today and Friday across southern San Bernardino County including the Morongo Basin, the Colorado River Valley, and across the Northwest Deserts of Mohave County including areas in and around Yucca, Wikieup, and Kingman. Moderate to high heat risk is expected in these areas with dangerously hot temperatures increasing the chance of those exposed for extended periods experiencing heat related illnesses. If working for long periods in the heat or participating in outdoor activities, be prepared to take precautions by taking more frequent breaks away from the heat if possible and increasing hydration. Over the weekend, moisture increasing across the south is expected to lower temperatures particularly if we also see the sun filtered by increasing debris clouds. A bit further north, the dangerously hot conditions are forecast to expand into parts of Clark and southern Nye counties over the weekend. An Excessive Heat Warning has been issued for these areas for Saturday and Sunday including the Las Vegas Valley, the Moapa Valley in northeastern Clark County, the Pahrump Valley in southern Nye County. The warning continues across the Lake Mead Recreational Area. For next week...monsoon moisture increases and thunderstorms return. [TROPICAL] As of the 1 am update this morning from the National Hurricane Center, the strength and track of Tropical Depression Fourteen-E remains similar to the previous forecast. It will undergo a few trajectory changes as the area of high pressure over the southern United States weakens. It is forecast to become a tropical storm today and a hurricane by early Sunday. The forecast track will essentially skirt it along the curve of western Mexico before pushing northwestward along the western edge of Baja California. As it does this, it will move into an area of reduced shear and warmer sea surface temperatures, which will likely be enough to allow it to strengthen into a hurricane this weekend, becoming Hurricane Nora. Forecast PWAT values associated with this system exceed 2 inches, which will allow PWAT values of 1.5-2.0" to overtake Sonora and 1.0- 1.5" to inch up the Colorado River Valley into southern Nevada and northwest Arizona. We will be able to get more specific with forecast details next week in the next few days. As it stands, we are expecting isolated to scattered thunderstorms across northwestern Arizona and the higher elevations of southern Nevada next week. [COMPARING 2021 NORA TO 2014 NORBERT] While it may be an obvious comparison to look back at the previous Hurricane Nora from September 16-26, 1997, a more intriguing comparison would be to Hurricane Norbert from September 6-9, 2014, which was a driving force for the catastrophic flooding in Moapa Valley, and ultimately led to the closure of a portion of Interstate 15. The similarities between the two systems will continue to be investigated by our staff over the next few days, but so far: - Very similar forecast tracks, with 2021 Hurricane Nora expected to hit the "sweet spot" just southwest of Baja California this weekend that would allow for a robust moisture flux into the Desert Southwest. - [2014] Hurricane Norbert was fueled by the remnants of Tropical Storm Dolly, a product of Atlantic Hurricane Season, that moved over northeastern Mexico just prior to Hurricane Norbert passing through the Baja. [2021] The National Hurricane Center is highlighting a disturbance approaching the Gulf of Mexico with a 50% chance of cyclone formation in the next 48 hours and 80% chance of cyclone formation in the next 5 days. The ECMWF Ensemble forecast shows PWAT values of 2.0-3.0" spreading across eastern Texas and northeastern Mexico, that would likely produce a similar moisture set up as experienced in 2014. However, the GEFS shows a further east track of the system, disallowing as much moisture to push westward. - [2014] Additional forcing aloft was experienced with remnant Norbert due to an incoming trough digging down from the Pacific Northwest. [2021] Ensemble forecasts allude to another trough dropping down from the Pacific Northwest Wednesday and Thursday of next week, which would coincide with forecast peak PWAT values. We will continue to assess the potential impacts of Tropical Depression Fourteen-E as confidence and details increase through the week. As it stands, best chances for precipitation are on Wednesday and Thursday. Stay tuned. && .AVIATION...For McCarran...Winds through mid-morning should favor southerly directions with speeds generally below 10 knots. Winds will shift more southwesterly and strengthen by late morning with gusts of 20-25 knots possible, before gradually easing again overnight. Skies will be mostly clear but lingering haze can be expected from regional wildfire activity. For the rest of southern Nevada, northwest Arizona and southeast California...Southwesterly breezes expected across much of the region today, strongest in the afternoon and evening hours. Gusts of 15 to 25 knots are likely, strongest near KDAG. Exception to the winds will be near KBIH where more typical diurnal wind patterns are expected along with lingering smoke, though significant visibility reductions are not anticipated. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && DISCUSSION...Salmen TROPICAL DISCUSSION...Varian AVIATION...Outler For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter
The national radar mosaic for the moment the first event began.
3 excessive heat. Local standard time, as filed.
Excessive Heat Warning criteria were reached four days in a row.
Excessive Heat Warning criteria were reached four days in a row.
Excessive Heat Warning criteria were reached five days in a row.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, 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: 981090, 981091, 981092.