Atmospheric river storm to bring heavy wind, rain to Northern California; warnings, advisories issued
By Carlos E. Castañeda
Portions of Northern California are bracing for a powerful atmospheric river storm beginning Tuesday night, with forecasters warning that the system is expected to be more disruptive due to its intense winds than its rainfall.
The National Weather Service issued a high wind warning for coastal areas north of the Golden Gate, including the Sonoma and Marin coastlines, where wind gusts could reach 60 to 65 mph. Isolated gusts of 65 to 70 mph are possible in a few spots, and forecasters urged residents to secure loose outdoor items and prepare for power outages. The warning is in effect from 10 p.m. Tuesday to 4 p.m. Wednesday.
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A broader wind advisory was in effect for the North Bay, San Francisco, the Peninsula, East Bay, and the Santa Cruz Mountains, where wind gusts are forecasted to range from 45 to 55 mph. Meanwhile, ahead of the storm’s arrival, a small craft advisory was in effect until 3 p.m. Tuesday, and a gale warning from 3 p.m. to 9 p.m., for San Francisco Bay, Monterey Bay, and coastal waters from Pigeon Point in San Mateo County to Point Piedras Blancas in San Luis Obispo County. A storm warning was issued from 9 p.m. Tuesday to 3 a.m. Wednesday for coastal waters from Point Arena in Mendocino County to Pigeon Point.
In its daily forecast discussion, the Weather Service said that while the wind is the primary concern, the cold front moving in later Tuesday evening and overnight will bring moderate to heavy rain, especially in the North Bay where the highest precipitation totals are expected, with amounts steadily decreasing moving south through the Bay Area.
The lower elevations in Sonoma, Marin, and Napa counties are forecast to receive between 1 to 2 inches of rain. Meanwhile, the higher terrain and coastal ranges of the North Bay will be the wettest spots, with rainfall totals between 1.5 and 2.5 inches, and some of the more prominent mountains potentially receiving just under 3 inches. Forecasters noted a “meaningful probability” of over 3 inches of rain across the coastal Sonoma County area between Sea Ranch and Bodega Bay.
The Central Coast and mountains are expected to see higher rain totals than the South Bay, with the Santa Cruz Mountains and the Santa Lucia Range/Big Sur Coast forecast to receive between 1 and 2.5 inches. For the general Central Coast and Bay Area, rain amounts are expected to average between 0.25 and 0.75 inches.
Tuesday began with a brief period of dense fog in the Salinas Valley, which quickly dissipated by mid-morning, leaving what forecasters described as “the proverbial calm before the storm.”
The Weather Service said there is a potential for nuisance flooding in urban and poor drainage areas, particularly in the North Bay where the heaviest rain is expected to fall during the Wednesday morning commute. However, the risk of widespread river flooding is low due to the progressive nature of the system and favorable pre-season soil moisture levels, the Weather Service said.
Chances of thunderstorms are in the 10 to 20% range, again, mainly over the North Bay, forecasters said. By Wednesday night, most of the rainfall will have passed, and the weather pattern is expected to shift to potentially dense radiation fog on Thursday morning, especially in the North Bay.
Bay Area temperatures on Tuesday will range from highs in the mid-60s to lows in the upper-50s along the coast and bayshore areas, with inland temperatures ranging from the upper-60s/low-70s to mid-50s/low 60s.
The Monterey Bay Area on Tuesday will see coastal temperatures range from the low- to mid-60s during the day to nighttime temps in the mid-50s. Inland and south areas including the Salinas Valley will see highs in the mid-60s Tuesday to lows in the low- to mid-50s range.
