Storm Summary Number 1 for West Coast Multi-Hazard Atmospheric
River Event
NWS Weather Prediction Center College Park MD
700 AM PST Thu Jan 05 2023

...Heavy rain/snow and high winds batter the West as an
atmospheric river flows into the West Coast...

Winter Storm Warnings are in effect for portions of the Sierra
Nevada.

Flood Warnings are in effect for areas of California north of the
Bay Area.

High Wind Warnings and Wind Advisories are in effect for portions
of California and Oregon.

Winter Weather Advisories are in effect for the east slopes of the
Cascades and areas lee of the Sierra Nevada.

Flood Watches are in effect for portions of California west of the
Sierra Nevada.

For a detailed graphical depiction of the latest watches, warnings
and advisories, please see www.weather.gov

At 600 AM PST...A low pressure center was analyzed about 300 miles
(~500 km) of the coast of Oregon with a minimum pressure of 968 mb
(28.59 in Hg). An occluded front extends to the southeast of this
low into the Central Valley of California, where there is a triple
point. From the triple point, a cold front extends to the south
through the Central Valley and into the Pacific Ocean just west of
Los Angeles, while a warm front was analyzed over the Sierra
Nevada mountains and into portions of the lower Colorado River
Valley. Latest surface observations and RADAR show a band of
moderate to heavy precipitation accompanied by high winds over
much of California. Upslope flow due to westerly winds interacting
with the Sierra Nevadas is currently enhancing precipitation west
of the mountain range. High winds in combination with the heavy
precipitation has contributed many reports of downed trees and
closed roads in California.

...Selected preliminary Storm Total Rainfall in inches from 700 AM
PST Wed Jan 04 through 600 AM PST Thu Jan 05...

...CALIFORNIA...
BURLINGAME 2.0 WSW                   2.96                    
MORAGA 2.4 NNW                       2.85                    
UKIAH MUNICIPAL APT                  2.64                    
K6BPM SANTA BARBARA                  2.36                    
ROHNERT PARK 0.9 SW                  2.30                    
ATASCADERO 2.3 NE                    2.13                    
THOUSAND OAKS 2.1 WSW                2.02                    
SACRAMENTO INTL APT                  1.63                    
SAN FRANCISCO INTL APT               1.61                    
LOS ANGELES INTL APT                 1.51                    
HOPLAND 8 SSE                        1.50                    
OXNARD NWS                           1.46                    
SANTA BARBARA MUNICIPAL APT          1.19                    

...Selected preliminary Peak Wind gusts in miles per hour earlier
in the event...

...CALIFORNIA...
KIRKWOOD MEADOWS 1.2 S                119                    
GRAPEVINE 3 SSE                       104                    
PULGA 2 NNW                           102                    
YORKVILLE 5.5 NW                       95                    
CAPETOWN 6 ENE                         94                    
HIGH GLADE LOOKOUT                     89                    
FERNDALE 6.4 S                         88                    
MAGIC MOUNTAIN TRUCK TRL               87                    
AMERICAN HOUSE 6 NW                    84                    
AGUA DULCE 8 S                         81                    
MOUNTAIN GATE 3 NNE                    72                    
CRESCENT CITY 1 ESE                    69                    
BLACK MOUNTAIN 7 E                     64                    


The low pressure center associated with this system will move
toward the north-northeast as it gradually weakens, with
significant impacts anticipated through tomorrow. Maximum rainfall
rates over California may exceed 1 inch per hour today, which has
been and will continue to result in flooding concerns for the
area. Heavy rainfall combined with various burn scars will
contribute to an elevated risk for flash flood concerns,
especially as it pertains to runoff and streamflows. In addition
to the heavy rain, heavy snowfall will continue to impact the
Sierra Nevadas, where maximum snowfall may exceed 1-2 feet through
Friday. Over time, the impacts from this event will shift toward
the north and east as the system disorganizes and dissociates
across the eastern Pacific Ocean. Moderate rain and heavy snowfall
is expected on Friday over Oregon and Washington, with multiple
feet of snow possible in locations higher than 7000 feet.

The next Storm Summary will be issued by the Weather Prediction
Center at 700 PM PST. Please refer to your local National Weather
Service office for additional information on this event.

Genz