After a brief break, another push of monsoon moisture fueled another round of thunderstorms over the Mojave Desert. Some storms produced flash flooding.
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The episode as NWS VEF wrote it up.
After a brief break, another push of monsoon moisture fueled another round of thunderstorms over the Mojave Desert. Some storms produced 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 Jul 30, 11:55 AM PST, 2 hours 54 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 1255 PM PDT Fri Jul 30 2021 .SYNOPSIS...Another episode of high monsoonal moisture is expected through the weekend which will lead to an increased threat of flash flooding and strong outflow winds. A Flash Flood Watch is in effect for much of the region through Sunday morning. Beginning late Sunday, drier conditions are expected to move in and result in several days of drier and warmer conditions through next week. && .SHORT TERM...Today through Sunday. Forecast for the next 48 hours is more or less on track with only minor changes. The most notable change was to include the Morongo Basin into the Flash Flood Watch for today and tomorrow. All in all, still on track for high moisture and a couple shortwave disturbances to affect the region today and possibly through Sunday which will bring an increased risk for monsoon thunderstorm impacts. Already at 19Z, up and down convection has led to outflow wind gusts of 40-50 mph and rainfall rates over an inch. There was some initial concern that extensive cloud cover will mitigate the development, or at least delay development, but differential heating appears to have been adequate to begin convection across Mohave and southern Nevada where breaks existed. Cloud cover is helping to stall convection in the Sierra Nevada but don't think this will last too long as much of that lift will be orographic/dynamical in nature vs thermodynamic. 12Z HREF continues to illustrate Inyo county convection producing stout outflow that spreads eastward both this afternoon and again tomorrow afternoon in response to each shortwave. Used a blend of the hi-res model wind fields to capture these trends. Also of note is the continued signal for highest QPF values across the Spring Mountains (and secondarily all the high terrain areas in the CWA). Both HREF, NBM, and WPC indicate 2+" total QPF for the Spring Mountains so concerns for the Mahogany Burn Scar are elevated as well through the weekend. Sunday, we begin to see drier air entraining into the western zones due to the Pacific low once the shortwave moves through. However, one more round of afternoon convection is likely for eastern zones as this moisture exits. WPC's marginal risk for Day 3 outlines this well and we may need to extend the FFA for Lincoln County through Sunday as well. Will let the midnight shift examine that further. && .LONG TERM...Next Week. Much of next week still looks rather quiet as significant dry air entrainment begins late Sunday and high pressure builds across southern CA and NV. PWAT anomalies go from well above average to below average over the course of the day on Monday in response to a low off the coast of California. Over the course of the week, moisture stays pretty much at bay, with some minor shortwave enhancement of winds during the afternoons Wednesday and Thursday. During that time, high pressure continues to build and temps rise to in response. Highs look to peak Wednesday and Thursday before we see some hints of moisture recovery late in the week and into the weekend. Longer range uncertainty still exists beyond Friday on whether moisture will return in earnest or be more gradual. Cluster analysis for Friday (Day 7) interestingly shows striking ensemble mean agreement with about a 50/50 split on this dry pattern continuing due to the presence of the Pacific low or this feature coming onshore over the Pacific northwest and weakening. Of the latter outcomes, only half of those (27% total) signal a return of enhanced QPF. CPC 8-14 day outlook shows this drier signal now indicated a slight favoring for below average precipitation beyond next week with above average temperatures as well. Makes sense given the trends seen in cluster analysis. && .AVIATION...For McCarran...Scattered thunderstorms will increase in coverage across the area this afternoon and evening. VCTS expected after 21Z today with thunderstorms beginning over the Spring Mountains and Sheep Range a bit earlier. CIGS will drop to around 8kft in and near any storms. The best chance for storms to directly impact the terminal is between 23Z and 03z Friday. Erratic winds can be expected near any storms. There is a chance of overnight storms with a preceding wind from the northwest after 03Z, but confidence in this is low at this time. After 09Z, storms will decrease in intensity. When storms are not impacting the terminal, expect light and diurnal winds with CIGS aoa 12kft. Showers and thunderstorms are also possible for Saturday and Sunday. For the rest of southern Nevada, northwest Arizona and southeast California...Scattered thunderstorms will impact most terminals as storms become more widespread through the evening into the overnight hours. Winds will be erratic with CIGS around 8kft near any thunderstorms. When storms are not around terminals, expect typical diurnal winds and periods of CIGS around 12kft. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant flash flooding impacts or wind gust/damage reports over the weekend. && DISCUSSIONS...TB3 AVIATION...Berc 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), 117 km away, was scanning. The volume nearest the first event began at 22:49 UTC.
4 flash flood. Local standard time, as filed.
The intersection of Highway 247 and Highway 62 was flooded.
Mud and rocks covered Highway 190.
The intersection of Highway 62 and Sunfair Road was flooded.
Water and mud covered the road at Zabriskie Point, and flooding was estimated to extend as far north as Furnace Creek.
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: 976204, 976205, 976206, 976207.