Low pressure over Southern California brought significant amounts of atmospheric moisture northward over the mountains, producing showers and thunderstorms with locally heavy rain and multiple reports of small hail. Heavy rain from thunderstorms over western Plumas County produced more than a dozen small debris flows along State Route 70, blocking the highway.
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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 STO wrote it up.
Low pressure over Southern California brought significant amounts of atmospheric moisture northward over the mountains, producing showers and thunderstorms with locally heavy rain and multiple reports of small hail. Heavy rain from thunderstorms over western Plumas County produced more than a dozen small debris flows along State Route 70, blocking the highway. There was also a rock slide with a large boulder at Donner Pass.
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 Sacramento, CA wrote its last area forecast discussion before the first event at Jun 9, 12:37 PM PST, 34 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 137 PM PDT Fri Jun 9 2023 .SYNOPSIS... Afternoon and evening thunderstorms through at least mid week. Sunday storms will be most numerous possibly into many valley locations. Temperatures will stay remain below normal then start increasing to near to slightly above normal by end of next week. && .DISCUSSION...Today through Monday. Minimal convection today as we are in transition from exiting upper low and next area of energy dropping south into the area. Saturday convection will be on the uptick once again as influence of upper low begins as low slides south along west coast. Precipitable water values increase above 100% for climatology by the end of the day. This will result in good shot of thunderstorms in the higher terrain and possibly into northern Sacramento Valley tomorrow afternoon. Biggest risk with these storms will be heavy rain and small hail...but storm movement should be fast enough that widespread impacts are not expected. Sunday looks to be the most active day as precipitable water values rise to around 200 percent as upper low will slide to SoCal placing us in good upward motion from the low. Can't rule out some rainfall rates approaching debris flow criteria in area burn scars but looks to be in the 20 to 40 percent chance range and a flash flood watch won't be issued at this time...but later shifts will want to look to see how things transform. Limiting factors will be that cells should move pretty quick. Monday...depending on how quickly the upper low decreases in strength should be impact wise pretty close to Sunday. Right now looks like slightly lower precipitable water values and lift synoptic level lift from low decreasing in strength a bit. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Ensembles and clusters again looking to be a good agreeemt and consistent that the upper low will begin shearing apart Tuesday and Wednesday. This leaves area under a weak upper trough. This will allow temperatures to climb to the mid to upper 80s with some lower 90s north Sacramento Valley by end of next week. Can't rule out some mountain convection with the weak westerly flow and the weak upper trough around...but should be mainly south of I-80 in Sierra. Rasch && .AVIATION... General VFR conditions expected over the next 24 hours. Local MVFR from low ceilings/marine intrusion possible in the Sacramento area 12Z-15Z Saturday (25-50% probability for ceilings less than 3 kft for KMCC, KMHR, KSAC, KSMF). Isolated to scattered showers and thunderstorms over the Sierra Nevada, southern Cascades, and Coastal Range through 03Z Saturday (15-25% probability), and again after 18Z Saturday, including the northern Sacramento Valley. The main threats are gusty and erratic winds and lightning expected near thunderstorms. Outside of thunderstorm influences, expect local southerly wind gusts up to 15-20 kts across portions of the Valley thru 06Z Saturday, and southwesterly up to 25-30 kts in the vicinity of the Delta through 12Z Saturday. && .STO WATCHES/WARNINGS/ADVISORIES... None. &&
Preliminary Local Storm Report
National Weather Service Sacramento CA
1236 PM PDT Fri Jun 9 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0611 AM Debris Flow 1 WNW Donner Peak 39.32N 120.33W
06/09/2023 Nevada CA Law Enforcement
California Highway Patrol-Truckee reported
the closure of portions of Donner Pass Road
(Old Highway 40) due to a rock slide/large
boulder in the road between Sugar Bowl and
Truckee after thunderstorms brought locally
heavy rain the day before.
&&
khThe national radar mosaic for the moment the first event began.
4 debris flow. Local standard time, as filed.
The California Highway Patrol-Truckee reported the closure of portions of Donner Pass Road (Old Highway 40) due to a rock slide/large boulder in the road between Sugar Bowl and Truckee after thunderstorms brought locally heavy rain the day before.
The California Highway Patrol reported State Route 89 approximately 3 miles north of Greenville Wye was blocked due to a debris flow at 4:08 PM on June 12. The road was opened to one way traffic by 4:19 PM on June 12, and was fully cleared to through traffic by 7:01 AM on June 13.
The California Highway Patrol reported multiple slides mud/dirt/rock on SR 70 east of Twain, completely blocking the roadway.
The California Highway Patrol reported multiple mud/dirt/rock slides west of Hot Springs Ravine on SR 70/Feather River Scenic Byway.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2023Every state in 2023This day in weather historyWarnings in California, June 2023
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: 1106217, 1106216, 1106214, 1106215.