Bay Area Thunderstorms and Showers in the Weather Forecast
Unsettled weather will continue across Northern California through the weekend, with mountain thunderstorms possible Thursday and Friday. Thursday is expected to be another warm day for inland areas, with temperatures widely expected to be in the 90s, before temperatures of 5 to 10 degrees are expected on Friday.
Scattered showers and a stray lightning strike are also possible around the Bay Area early Thursday morning, as well as scattered thunderstorms possible along the Santa Cruz Mountains and San Francisco Peninsula Friday afternoon.
Thunderstorm Thursday morning
Some weather models predict scattered rain and thunderstorms in the Gulf region on Thursday morning.
WeatherbellMonsoon moisture from the Desert Southwest continues to rise over central California, sending high clouds toward the Bay Area. This subtropical air is supportive of scattered thunderstorms, meaning heavy rain and lightning strikes are possible Thursday morning.
Although the probability is low, the atmosphere will be more conducive to thunderstorms over the East Bay, South Bay and Peninsula. While the exact timing of the storms is uncertain, the most likely period will be between 6 a.m. and noon.
The unstable atmosphere could also disrupt the marine layer, meaning coastal cities could wake up to fog-free skies. An isolated thunderstorm is also possible over the Diablo Range in the East Bay in the late afternoon.
Coastal convection on Friday
The US weather model forecasts scattered rain across the Gulf region on Friday afternoon.
Baron/LynxAn unusually strong low pressure system is expected to strengthen along the Central Coast Thursday night into Friday, increasing the potential for summer rain in the Bay Area on Friday.
Weather models indicate that the lowest pressure will be near Point Conception, meaning some coastal areas will have unstable conditions to support thunderstorms on Friday. Cumulus clouds will likely start appearing over the mountains around lunchtime. By the afternoon and evening, light rain and even stray lightning strikes are possible.
The Marin Headlands, San Francisco, Santa Cruz Mountains and the coastal range in San Mateo County are likely to see thunderstorms, but light rain is possible in the South Bay. While no measurable rain is expected in the East Bay, the impact of rain could be enough to make roads slippery.
Tropical Storm Hillary
The Bay Area is not far from thunderstorms and rain chances after Friday. While Saturday will likely see a lull in active weather, Tropical Storm Hillary is expected to impact California by Sunday and continue into early next week.
As more information becomes available, The Chronicle will continue to provide updates.
Thursday collapse
San Francisco: Outer Sunset and Richmond residents along the Great Highway can hear rumbles of thunder from an isolated thunderstorm off the coast between 6 a.m. and noon. Look for cloudy skies on the west side and partly cloudy skies east of Sutro Tower.
The sunny time of day will be from noon to 4 p.m., and the warm, humid air will allow daytime temperatures to reach the high 60s by the water and 70 degrees downtown. Winds will reach 30 mph around Ocean Beach, Presidio, and Twin Peaks throughout the afternoon.
A combination of marine fog and puffy cumulus clouds can make for a stunning sunset in Dolores Park. Look for foggy conditions tonight with temperatures dropping to the low 60s.
East Bay: Weather models predict the possibility of scattered rain and thunderstorms in the morning hours for residents of the Tri-Valley area. Look for sunny skies and humid weather in the afternoon. Residents in Walnut Creek, Concord and Dublin can expect daytime temperatures in the mid to mid 90s.
The Gulf Breeze will bring partly cloudy skies along the I-80 and I-880 corridors. Residents in Richmond, Oakland and Fremont can expect wind gusts of 20 mph from 1pm to 6pm and afternoon highs in the mid 70s.
The offshore clouds return in the evening, just in time for a beautiful sunset. Expect overnight temperatures to drop into the upper 50s by the water and lower to the 60s inland.
North Bay: Isolated thunderstorms are possible over Solano County and the interior valleys of Napa and Sonoma Counties this morning. Wind speeds could briefly reach 20 mph in some showers before fading. Residents along the Sonoma and Marin County coast can expect fog and drizzle until 11 a.m
Sunni skies return in the afternoon. Residents in Sausalito can expect a light breeze along San Pablo Bay with daytime highs remaining in the upper 60s, while inland residents of Vallejo, Novato and San Rafael can expect warmer winds pushing temperatures into the upper 70s. Residents in the Wine Country — Santa Rosa, Napa and Petaluma — can expect warm, humid weather for most of the afternoon with daytime temperatures reaching the low to mid 80s.
Scattered clouds will bring a beautiful sunset over the area, while fog will return to the Gulf shore in the evening. Look for overnight lows in the upper 50s near the water and lower 60s inland.
Pacific coast and peninsula: There is a slight chance of rain in the morning, with a possible thunderclap or two by the water. Any morning fog will be mostly limited to Highway 1 – Daly City, Pacifica and Half Moon Bay.
Drier weather returns after 1pm. Look for partly cloudy skies and daytime highs in the upper 60s along the coast and lower to mid 70s in the San Bruno Gap – Colma, Millbrae and south San Francisco. Residents along I-280 and Highway 101 can expect a mix of warm and humid weather, with daytime temperatures reaching the upper 70s to lower 80s.
Fog and cool air return to the peninsula in the evening. Expect nighttime temperatures in the mid 50s next to the water and upper 50s to 60s inland.
South Bay and Santa Cruz: Santa Clara Valley residents can look for isolated thunderstorms this morning. There are accumulations of a few hundredths of an inch of rain in the Cupertino and Millbrae Hills and the eastern foothills of the valley. Some isolated rain is possible in the Santa Cruz Mountains, but chances there remain low.
Sunny skies arrive in the afternoon across Santa Clara and Santa Cruz counties. Look for a humid afternoon with daytime highs in the lower 80s in the Santa Cruz Mountains and mid 80s in the valleys. The cold air will keep temperatures near 70 degrees for residents along Monterey Bay.
Fog and cold air spread inland after sunset. Look for overnight lows in the lower 60s near the water and mid 60s inland.
Contact Anthony Edwards: anthony.edwards@sfchronicle.com Contact Gerry Diaz: gerry.diaz@sfchronicle.com
