A moist east-southeast flow prevailed over Central California in early August as persistent strong high pressure was centered over the Great Basin. As a result, a surge of tropical moisture spread into the area between the afternoon of August 2 and the early morning of August 4.
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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.
A moist east-southeast flow prevailed over Central California in early August as persistent strong high pressure was centered over the Great Basin. As a result, a surge of tropical moisture spread into the area between the afternoon of August 2 and the early morning of August 4. Showers and thunderstorms were prevalent over the mountains, Kern County Deserts and south end of the San Joaquin Valley on August 2 and into the Central San Joaquin Valley on the evening of August 3 and into the morning of August 4. Slow moving thunderstorms produced flash flooding in the Tehachapi area during the afternoon of August 3.
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 Aug 2, 1:04 PM PST, 21 minutes earlier.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 204 PM PDT Wed Aug 2 2017 .SYNOPSIS... A ridge of high pressure will remain over the western states while a area of low pressure remains west of the California coast through Friday. The resultant easterly flow will keep monsoonal moisture in place for a continued threat of thunderstorms. The low will move to the north later this weekend with the winds aloft shifting to the southwest bringing drier air. && .DISCUSSION... A ridge of high pressure will remain over the western states with an area of low pressure off the southern California coast through Thursday. An east-southeasterly flow around these systems has been drawing subtropical moisture northward yesterday and today. This is creating a complex pattern over the forecast area, with very moist air across the south and drier air across the north. Most of the moisture remained to our south Tuesday, but has pushed northward into Kern County today. A band of precipitation moved northward into the desert areas this morning and has continued to move north across the mountains and into the southern San Joaquin Valley this afternoon. This band has mostly been light showers with just a few brief thunderstorms so far this afternoon, but additional develop will need to be watched closely as thunderstorms could produce heavy rain. This band is expected to continue to move slowly northwest the remainder of this afternoon and evening. The big question is how far north will it go before it falls apart. Hi-res models are indicating that it could move north into into Fresno county this evening, so have maintained slight chance pops from Fresno southward. Mid-level moisture will continue to move into the area Thursday, keeping the chance of showers and thunderstorms going across Kern County through the early evening. In addition, thunderstorms are developing across the Sierra Nevada this afternoon. Expect these storms to continue through the evening hours and then redevelop again Thursday afternoon as plenty of moisture and instability remain in place. The temperature forecast is complicated by the clouds moving up from the south as well as any clouds that drift off the Sierra. Most of the northern part of the San Joaquin Valley has been cloud free today while the south valley has become mostly cloudy. With very warm overnight temperatures last night, we had a head start with the warming and many areas in the valley have reached or exceeded 100 degrees already. Bakersfield reached 100 by 11 am, but then the warming stopped as the clouds increased. Expect there to be enough cloud cover around to keep minimum temperatures quite warm again tonight but afternoon highs down a few degrees Thursday. Expect highs in the San Joaquin Valley to be generally 100-103 degrees Thursday. The low off the coast will move northward Friday and Saturday, turning the flow aloft more southerly and then southwesterly and ending the influx of moisture into the central California interior. However, enough moisture and instability remain for convection to continue over the Sierra each afternoon and evening through early next week. Temperatures Friday through next Wednesday are expected to change little from day to day with highs in the San Joaquin Valley near 100 degrees. && .AVIATION... In the Sierra Nevada, a chance of afternoon thunderstorms through 06z Thursday and again after 18z Thursday. In the Kern County Mountains and Desert areas, a chance of showers and thunderstorms through 00z Friday. In the San Joaquin Valley, a slight chance of showers and thunderstorms through 06z Thursday from Fresno County southward. A slight chance of showers and thunderstorms continues over Kern County through 00z Friday. Otherwise, VFR conditions will prevail across the Central CA Interior during the next 24 hours. && .AIR QUALITY ISSUES... On Wednesday August 2 2017... Unhealthy for sensitive groups in Fresno... Kern and Tulare Counties. Further information is available at Valleyair.org && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. 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...Bean avn/fw...Bean synopsis...Bean weather.gov/hanford
The San Joaquin Valley radar (KHNX), 171 km away, was scanning. The volume nearest the first event began at 21:26 UTC.
2 flash flood, 1 heavy rain, 1 hail, 1 debris flow. Local standard time, as filed.
The White Wolf RAWS measured 1.02 inches of rainfall from a slow moving thunderstorm.
Rangers at Yosemite National Park reported hail covering State Highway 120 (Tioga Road).
California Highway Patrol reported rocks and mud covering roads 7 miles southeast of Tehachapi.
Water was covering several roadways in and around Tehachapi.
California Highway Patrol reported up to 4 inches of water on State Highway 58 east of Tehachapi and debris and mud flowing onto smaller nearby roadways.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2017Every state in 2017This day in weather historyWarnings in California, August 2017
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: 715332, 715328, 715316, 715311, 715322.