Isolated thunderstorms developed over the higher elevations of the Southern Sierra Nevada during the afternoon of May 21. A hiker on the cables of Half Dome in Yosemite National Park slipped and fell off of the cables during a thunderstorm while the surface was wet at around 330 pm PST.
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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 HNX wrote it up.
Isolated thunderstorms developed over the higher elevations of the Southern Sierra Nevada during the afternoon of May 21. A hiker on the cables of Half Dome in Yosemite National Park slipped and fell off of the cables during a thunderstorm while the surface was wet at around 330 pm PST. The nearest weather station reported 0.32 inches of rainfall between 300 pm PST and 400 pm PST.
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 Hanford, CA wrote its last area forecast discussion before the first event at May 14, 2:01 PM PST, 59 minutes earlier.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 301 PM PDT Mon May 14 2018 .SYNOPSIS... Scattered showers and isolated afternoon and early evening thunderstorms will occur over the higher elevations of the Sierra each day through Sunday. Otherwise, dry weather will prevail over the central California interior during the period. Seasonal temperatures can be expected through Tuesday before trending cooler than normal Wednesday with a gradual warming trend through the weekend. && .DISCUSSION... A Rex block has set up across the western third of the US...with a closed low over Nevada and a ridge of high pressure over the Pacific NW. Diurnal convection will continue to create scattered showers across the central Sierra through Thursday as the low center over Nevada slowly fills and is replaced by another low center...currently off the west coast. Still not been seeing much lightning across the Sierra in the afternoons...however isolated storms are not out of the question. Models remain in decent agreement that the low center will hold in place over Nevada through Tuesday. The ridge across the Pacific NW will take over as the low fills and dissipates Tuesday. Models still show the eastern Pacific low moving across northern CA on Wednesday and into NV Friday. This upper low center will again increase the chances of convection in the Sierra. Temps will be well below normal on Wednesday as the low crosses over the area with increased cloud cover and lower heights. We are holding off for any precip in the SJV at this time...confidence remains low. Some guidance is indicating a chance of light rain across Merced county on Wednesday, but as we mentioned, confidence remains low. A zonal flow pattern sets up across the region on Saturday and continues into Monday with a broad shallow trough pattern across most of the western US. Guidance is trying to dry the Sierra out on Monday with only a few showers possible on Sunday...mainly along the crest. Temperatures are expected to gradually warm through the weekend to just above normal, but still staying below 90 in the SJV. && .AVIATION... Areas of MVFR and local mountain obscuring IFR in low clouds and showers over the Southern Sierra Nevada with isolated thunderstorms possible through 03Z Tuesday. Otherwise...VFR conditions will prevail across the Central CA Interior during the next 24 hours. && .AIR QUALITY ISSUES... None. && .CERTAINTY... The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is high. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.php for additional information an/or to provide feedback. && .HNX Watches/Warnings/Advisories... NONE. && public...Bentzien avn/fw...Bentzien synopsis...Bentzien weather.gov/hanford
The national radar mosaic for the moment the first event began.
1 heavy rain. Local standard time, as filed.
Report on Twitter that a hiker on the cables of Half Dome in Yosemite National Park slipped and fell off of the cables during a thunderstorm. The hiker was found dead from the fall the next day after a search and rescue was performed.
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 |
|---|---|---|---|---|---|
| Heavy Rain, Mariposa | 2018-05-21 | Male | Outside/Open Areas | Indirect |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2018Every state in 2018This day in weather historyWarnings in California, May 2018
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: 748170.