A low pressure system centered over southern Nevada provided for a shallow surge of mid-level moisture into central California On September 3 and 4. During the afternoon of the 4th, several thunderstorms developed over the higher elevations of the Southern Sierra Nevada from Yosemite National Park southward to the Lake Isabella area where the atmosphere was unstable.
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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 low pressure system centered over southern Nevada provided for a shallow surge of mid-level moisture into central California On September 3 and 4. During the afternoon of the 4th, several thunderstorms developed over the higher elevations of the Southern Sierra Nevada from Yosemite National Park southward to the Lake Isabella area where the atmosphere was unstable. Heavy rainfall was produced by thunderstorms near Kings Canyon and near Lake Isabella which over an inch of rainfall between 100 pm PDT and 5 pm PDT. In addition, isolated thunderstorms brought some light rainfall to the southern Sierra foothills and to the Kern County Deserts.
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 Sep 4, 1:06 AM PST, 1 hour 24 minutes earlier.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 206 AM PDT Tue Sep 4 2018 .SYNOPSIS...A weak trough of low pressure will allow for thunderstorms to form over the Sierra Nevada. This system will slowly move east on Wednesday, but lingering instability will keep a small threat of storms in the forecast for the Sierra. By Thursday, drier air aloft and building high pressure will end the threat of thunder. Over the remainder of the area dry weather will continue for the next several days. && .DISCUSSION...Some light showers due to a decaying thunderstorm complex over the Owens Valley have been slowly moving south tonight. Due to this feature, some mid level clouds will push from the east over the Sierra early this morning and into the east side of the San Joaquin Valley. Isolated to scattered showers and thunderstorms are expected to develop over the Sierra Nevada crest this afternoon as sufficient instability and mid-level moisture are in place with the presence of the weak upper-level trough. Otherwise, expect warmer than average daytime highs to continue across the Central California interior. Highs could once again reach in the triple digits in the warmest areas of the Central Valley today. As the trough slowly moves into the Great Basin on Wednesday, some residual moisture and instability will keep the threat for showers and thunderstorms over the Sierra, although we are anticipating lesser coverage compared to this afternoon/evening. Afterward, high pressure will expand inland from the Eastern Pacific, including on Thursday and at least through Saturday. So, it appears a rather warm period is in store for at least the next several days. A dry southwest flow is expected to prevail during late this week. Models are in decent overall agreement and show a flattening of the East Pacific ridge of high pressure by Sunday and early next week. Flow aloft will turn more onshore, while a fairly strong upper-level low moves over the Pacific Northwest. It will likely remain warmer than average with a modest lowering of temperatures during this period. However, models differ in terms of the strength of the ridge of high pressure over the East Pacific and into Southern California and the Desert Southwest, and am not counting on a big change in the overall pattern for now. && .AVIATION... Areas of MVFR in haze, mainly north of Fresno County. Scattered thunderstorms will occur over the Sierra Nevada between 18z this afternoon and 06Z Wednesday, with possible local terrain obscuration in heavy rain. Otherwise, generally VFR conditions can be expected throughout the Central California interior during the next 24 hours. && .AIR QUALITY ISSUES... On Tuesday September 4 2018... Unhealthy for sensitive groups in Fresno... Kern and Tulare Counties and Sequoia National Park and Forest. Further information is available at Valleyair.org && .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...BSO avn/fw...JEB synopsis...BSO weather.gov/hanford
The national radar mosaic for the moment the first event began.
2 heavy rain. Local standard time, as filed.
A slow moving thunderstorm produced 1.07 inches of rainfall at Lake Isabella between 330 pm PDT and 430 pm PDT.
Sugarloaf RAWS measured 1.10 inches of rainfall between 111 pm PDT and 511 pm PDT. More than half of the rain fell between 211 pm PDT and 311 pm PDT while a slow moving thunderstorm impacted the area.
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, September 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: 772635, 772632.