An unseasonably strong upper level low tracked over southern Oregon and northern California from August 09 through August 11. A series of shortwave troughs brought showers and thunderstorms to the region which produced damaging winds, severe hail, and abundant lightning.
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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.
An unseasonably strong upper level low tracked over southern Oregon and northern California from August 09 through August 11. A series of shortwave troughs brought showers and thunderstorms to the region which produced damaging winds, severe hail, and abundant lightning. Law enforcement reported many large tree branches, up to the size of a car at times, blocking roadways including state route 299. Wind gusts appear to be sub-severe, between 25-35 mph, and were estimated via radar, observations, and the unrestricted mesoscale analysis (URMA). Additionally, this system was responsible for starting multiple wildfires by lightning, but most fires were under 0.5 acres and fire crews were able to extinguish or control these fires.
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 Aug 9, 2:45 PM PST, 8 hours 12 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 345 PM PDT Fri Aug 9 2019 .SYNOPSIS... Chance of showers and thunderstorms over the Coastal and Shasta mountains/foothills, and possibly over the Northern Sacramento Valley through Saturday, then dry through the remainder of the extended period. Continued cooling trend through Saturday with daytime temperatures well below normal. Warming to near normal early next week. && .DISCUSSION... Continuous CG strikes occurring offshore near the upper low center vcnty of 40N/128W. A band of clouds (and weak echoes on radar with possible sprinkles) has been moving over Norcal since this morning as a short wave moves Nwd out ahead of the upper low. Around 130 pm, the short wave triggered a cluster of storms in Wrn Siskiyou Co N of our CWA. The short wave will be lifting NEwd out of the region by early evening, thus we will have to wait for the upper low to move closer to the coast (probably closer to 03z to 06z or so) before seeing higher dBz echoes in our CWA. This has been indicated by the HREF Probability of >40 dBz and generally by the NAM 3km Model REF progs. The unseasonably deep upper low (-2 to -3, 5H height anomaly, a 2-5 yr return interval, and a -2 to -3.5 temp anomaly) over the Ern Pac will be moving over Norcal on Sat increasing the chances of convection in our CWA. Generally, the chance of showers/storms should be along/north of a line from Lake Co to Red Bluff to the "Tri-City Metroplex" of Mineral-Chester-Quincy during the day on Saturday. PWs are forecast to increase to over an inch on Sat, so the storms should have some rainfall associated with them. There is a big difference in the amount of QPF between the GEFS/ECMWF (GEFS much drier) and we have nudged the QPFs to the NBM, and even went a little wetter along the western Shasta Co border, per the "Elevated Instability 4-Panel" progs and HREF dBz probability which suggest the coastal range from Wrn Tehama to Wrn Shasta Co are the most likely areas in our CWA to see a chance of storms Fri nite into early Sat morning, before the activity shifts NEwd on Sat. Models maintain a closed upper low circulation into at least mid-day Sat which may tend to keep convection going into Sat, at least over Shasta Co until the upper trof axis has passed in deference to the model instability progs. The upper low opens and shifts northeast of the state Sat night ending the shower/storm threat. Max temps are mostly trending cooler than yesterday and are forecast to run about 7 to 14 degrees below normal today, with additional cooling forecast for Sat as the offshore low moves inland. Max temps are expected to range 8 to as much as 20 degrees below normal on Sat, given the strong temp anomaly mentioned above. Around midday, the Ft Ord profiler showed an elevated marine layer around 3000 ft which means some strato-cu with bases 1500-3500 ft could spread into the Vly Sat morning given the synoptic influence of the approaching upper level low. Flat ridging behind the exiting upper low will bring warming on Sun although max temps will still generally run several degrees below normal. Airmass warming on Mon will return highs to near or a little above normal. JHM && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... While a transient upper ridge will be flattening on Tuesday, another day of warmth is in the forecast as Valley highs stay in the mid/upper 90s. However, a gradual cooling trend is expected across interior northern California thereafter. A rather amplified trough digs down from British Columbia which eventually settles over the West Coast by mid-week. While individual forecast models vary in placement and amplitude, there is a fairly high signal in the ensemble guidance of this feature. Consequently, temperatures will gradually begin to decrease throughout the week, particularly by Thursday and Friday as highs could sit 3 to 7 degrees below average for mid-August. While slow moving in nature, the upper trough should eventually exit into the interior western U.S. by the start of next weekend. Overall impacts beyond cooler temperatures are unknown at this juncture, but details including thunderstorm chances will become more apparent in future forecasts. ~BRO && .AVIATION... Mostly VFR conditions expected to prevail overnight. Isolated thunderstorms possible over Northern California tonight and into Saturday, including KRDD and KRBL. Potential for MVFR ceilings below 2,000 ft over the Sacramento/Delta region southwards to KMOD Saturday morning. && .STO WATCHES/WARNINGS/ADVISORIES... None. &&
Special Weather Statement National Weather Service Sacramento CA 1145 PM PDT Fri Aug 9 2019 CAZ015-063-100730- Northern Sacramento Valley-Mountains Southwestern Shasta County to Northern Lake County- 1145 PM PDT Fri Aug 9 2019 ...A CLUSTER OF STRONG THUNDERSTORMS WILL AFFECT NORTH CENTRAL TEHAMA AND SOUTH CENTRAL SHASTA COUNTIES... At 1144 PM PDT, a cluster of strong thunderstorms were located near Blossom, or 9 miles west of Red Bluff, moving north at 30 mph. Winds in excess of 30 mph and nickel size hail are possible with these storms. Locations impacted include... Red Bluff, Rosewood and Blossom. LAT...LON 4002 12233 4008 12264 4041 12256 4035 12219 TIME...MOT...LOC 0644Z 197DEG 26KT 4013 12242 EH
The Beale AFB radar (KBBX), 101 km away, was scanning. The volume nearest the first event began at 06:58 UTC.
2 hail. Local standard time, as filed.
On Friday, August 9, roughly 7 miles to the northwest of Red Bluff, a strong thunderstorm produced 1 inch hail stones that fell for 5 to 10 minutes. The public reported that they noticed some minor damage to trees and plants in the area.
A severe thunderstorm produced up to 1.5 inch diameter hail stones on the north side of Black Butte Lake near the Buck Horn Campground. The time stamp for this report was estimated by radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2019Every state in 2019This day in weather historyWarnings in California, August 2019
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: 854509, 854510.