Cold low pressure passing overhead helped trigger isolated thunderstorms over the Mojave Desert. A couple of storms caused damage.
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The episode as NWS VEF wrote it up.
Cold low pressure passing overhead helped trigger isolated thunderstorms over the Mojave Desert. A couple of storms caused damage.
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 Sep 20, 8:39 AM PST, 49 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 939 AM PDT Fri Sep 20 2024 .SYNOPSIS...A low pressure system moving through the Mojave Desert will bring scattered to numerous showers and thunderstorms to much of the region today and tonight. Brief heavy rainfall is possible with the stronger storms along with gusty winds. Drier conditions will resume Saturday onward with a warming trend commencing. && .UPDATE...Isolated showers and thunderstorms that developed over the western Las Vegas Valley around sunrise have since moved west- northwestward and are weakening in western Clark County. Latest development is concentrated in southeast Inyo, northern San Bernardino County and near Yucca Valley. Diffluent flow/cold air aloft associated with the upper low presently over Los Angles will continue to drive storm development over southeast California the rest of this morning through the afternoon. New showers and thunderstorms will eventually start to develop and expand in coverage over southern Nevada and northwest Arizona this afternoon through tonight as the upper low moves east through western Arizona tonight. There may be a few showers lingering in eastern Clark and southeast Lincoln County tomorrow morning through 8 am PDT, otherwise any shower coverage will be confined to northwest Arizona tomorrow. Sent out an updated forecast package using guidance from the 12Z convective allowing models. && .PREV DISCUSSION...122 AM PDT Fri Sep 20 2024 .SHORT TERM...through Sunday night. Closed low currently located near the Los Angeles Metro area will swing eastward today across the Mojave Desert and into northern Arizona by Saturday morning. As the low passes through, cold air aloft, modest but elevated moisture content, and strong dynamically driven lift will encourage widespread showers and thunderstorms across the region. Precipitation coverage through mid-afternoon will largely favor the San Bernardino County Deserts including Barstow- Daggett, Baker, and the Morongo Basin. CAPE values across these areas will climb into the 500-750 j/kg range resulting in isolated stronger storm cores, and with 500mb temps of -15 to -16C, a few instances of small hail are possible as well. By this evening, as the low shifts into the lower Colorado River Valley, strongest divergence aloft and overall most favorable upper level forcing will move into southern Nevada and northwest Arizona. Sunset through midnight represents the approximate best window for precipitation in the Las Vegas metro, with showers and thunderstorms tending to taper from west to east late Friday night into Saturday morning. Instability won't be quite as significant after dark which suggests a tendency for more dominant shower activity as opposed to thunderstorms after sunset, though a few lightning strikes will remain possible well into the night. In addition, with lingering dry air in the low levels, locally gusty winds will be possible especially in advance of the developing shower activity. Overall precipitation expectations remain fairly minimal, with a trace to a tenth of an inch most common, though some areas observing stronger storms especially across San Bernardino and Mohave counties could see locally heavier rainfall totals. Aside from some lingering morning showers in Mohave County, drier conditions will resume over the weekend as the low departs to our east. Temperatures remain slightly below normal on Saturday before returning closer to normal Sunday as heights climb slightly. .LONG TERM...Monday through Thursday. Models are in much poorer agreement than 24 hours ago, and the overall forecast pattern has changed somewhat, so confidence is lower than average. Although there is general consensus on high pressure moving into the West from the Pacific, there are important differences on the east side of the ridge. Several of the ensemble members have now latched onto one or more of the following ideas: weak low pressure developing on the southern flank of the high in the area of Southern California, tempering our warming trend and introducing some clouds, and/or another shortwave trough diving down the front side of the ridge, amplifying over the Four Corners area and possibly retrograding westward, which would bring a chance of light rain showers to at least our eastern CWA. That being said, a majority of the ensemble members still keep our area dry, so there's only a slight chance at the moment. Run to run trends will be important. Temperatures should still rise above normal in areas which don't see showers, although not quite to the degree which was expected earlier. The most likely scenario should be highs in the mid 90s for Las Vegas, but a few degrees cooler if substantial cloud cover materializes. && .AVIATION...For Harry Reid...Light winds this morning will turn southeast by mid-day and continue from that direction into the early evening. Once the winds turn to the southeast, sustained wind speeds of 7 to 11 knots are anticipated, and there is a 30% probability of occasional gusts to 15 knots after 21Z. Scattered showers and a few isolated thunderstorms are also expected this evening and early tonight, with the best chance of thunderstorms occurring after sunset. Storm chances should end by 08Z, but a few showers may linger through the night. Prevailing winds are expected to turn southwest after sunset, but gusty outflow winds from any storms that do develop could impact the terminal area through the evening night. Sky conditions will range from scattered to broken today with bases AOA 8kft AGL, followed by improving skies overnight with bases lifting to around 12kft AGL by daybreak Saturday. For the rest of southern Nevada, northwest Arizona and southeast California...Low pressure moving across southern California today and northwest Arizona overnight will bring the threat of showers and thunderstorms to the region. KDAG will see showers and storms develop early this afternoon, followed by the Colorado River TAF sites by late afternoon and early evening. A few storms are also possible in the Las Vegas Valley after sunset. Conditions will improve by Saturday morning, with all but the far eastern sections of the region seeing precipitation chances end. Aside from gusty winds near thunderstorms, winds will be from the southeast to southwest in most areas, with sustained speeds of 12 knots or less. Winds at KBIH will be primarily from the north through the TAF period. Sky conditions will range from scattered to broken today with bases AOA 8kft to 10kft AGL, followed by improving skies west to east overnight with bases lifting to around 12kft AGL by daybreak Saturday. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && UPDATE...Pierce SHORT TERM...Outler LONG TERM...Morgan AVIATION...Planz 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), 118 km away, was scanning. The volume nearest the first event began at 17:27 UTC.
1 flash flood, 1 lightning. Local standard time, as filed.
Highway 127 was impassable due to being flooded with 1.5 feet of water plus rocks and debris. One car with four occupants was stuck and water was coming into the car.
Lightning set fire to a transformer.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2024Every state in 2024This day in weather historyWarnings in California, September 2024
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: 1216216, 1216217.