An upper low pressure system strengthened off the Pacific Northwest coast on March 12. This system spread moisture into Central California on March 13 and 14 as a deep upper trough slowly pushed east across the region.
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The episode as NWS HNX wrote it up.
An upper low pressure system strengthened off the Pacific Northwest coast on March 12. This system spread moisture into Central California on March 13 and 14 as a deep upper trough slowly pushed east across the region. Scattered thunderstorms developed during the afternoon of March 13, and one strong thunderstorm which developed in the Southern Sierra Foothills in Tulare County produced heavy rainfall which resulted in Flash Flooding and mudslides near the Pier Fire burn scar near Springville. Mudslides were also reported near the Detwiler Fire burn scar near Mariposa. Several locations in the southern Sierra Nevada measure between an inch to two inches of rainfall. Several inches of new snow fell over the higher elevations of the Southern Sierra Nevada and Tehachapi Mountains with the snow level lowering to 5000 feet on the 14th.
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 Mar 12, 12:34 PM PST, 13 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 134 PM PDT Mon Mar 12 2018 .SYNOPSIS... A series of potent storms will impact the central California interior for the rest of this week. Moderate to heavy precipitation can be expected at times. The unsettled weather will continue into next weekend with below normal temperatures across the region. Winter Weather Advisories and Warnings remain in effect for parts of the Sierra Nevada Mountains. && .DISCUSSION... Large mid/upper level low to usher in plenty of moisture and strong orographics into the Sierra Nevada range beginning on Tuesday. First notable feature will be 110-120 knot jet cutting over central California by Tuesday afternoon. ECMWF depicts this jet well with at least northern Forecast Area under the influence of Left Front Quadrant. This will provide plenty of lift into the west slopes of Sierra through Tuesday night. During this time, snow levels in the Sierra should be 7.5-8kft. However, these snow levels should drop rather quickly by Wednesday as colder air begins to circulate around this system. Also circulating around this mid/upper level low will be shortwaves with additional moisture. It's really hard to pinpoint when central California will be getting a decent break in the precipitation. More of the certainty currently lies with later Tuesday with liquid totals of a few inches in the high Sierra. As for the San Joaquin Valley, rainfall amounts to approach one inch from Hanford/Visalia northward...with lesser amounts across Kern County. Again for Wednesday, precipitation timing could be tricky. Will let later forecast shifts take a closer look. One thing for sure, snow levels should drop between 4-4.5kft by Wednesday night. Will have to watch Grapvine area, specifically Tejon Pass if next round of precipitation moves in by then. After Wednesday night, models maintain a troughy pattern along the west coast through the end of the week and into next weekend, but differ in timing and strength of shortwave impulses tracking inland. Confidence is increasing that Friday and Friday night will be wet for most areas. && .AVIATION... VFR conditions will become MVFR by Tuesday afternoon, especially across the higher foothills of the Sierra Nevada. Until then, mid to high level clouds can be expected with a generally light surface wind. && .AIR QUALITY ISSUES... None. && .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... Winter Weather Advisory from 2 PM Tuesday to 11 PM PDT Wednesday ABOVE 6500 FEET FOR THE CAZ097. Winter Storm Warning from 1 PM Tuesday to 11 PM PDT Wednesday ABOVE 6000 FEET FOR THE CAZ096. && public...Lynott avn/fw...Lynott synopsis...Lynott weather.gov/hanford
The San Joaquin Valley radar (KHNX), 151 km away, was scanning. The volume nearest the first event began at 10:17 UTC.
2 flood, 2 heavy rain, 1 debris flow, 1 funnel cloud. Local standard time, as filed.
California Highway Patrol reported a mudslide caused a partial closure of State Highway 49 near Bagby.
California Highway Patrol reported Flash Flooding and a mudslide on State Route 190 east of Springville at the Powerhouse Bridge. About 3 feet of water covered the bridge.
Media report of a mudslide near the intersection of Road 284 and Worth Dr.
California Highway Patrol reported State Highway 41 was closed due to rocks blocking the road. Fish Camp measured 1.65 inches of rain on March 13.
Media report of a funnel cloud at Wind Wolves Reserve.
California Highway Patrol reported boulders blocking the east bound portion of State Route 178.
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, March 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: 734742, 734737, 734738, 734740, 734739, 734741.