Marine Weather Net

San Francisco Bay South of the Bay Bridge Marine Forecast


10 - 20


10 - 20


10 - 20


5 - 15

The Marine Weather Forecast In Detail:
PZZ531 Forecast Issued: 850 AM PDT Fri Sep 25 2020

Today...W Winds 10 To 20 Kt.
Tonight...W Winds 10 To 20 Kt With Gusts Up To 25 Kt.
Sat...W Winds 10 To 20 Kt With Gusts Up To 25 Kt.
Sat Night...W Winds 5 To 15 Kt.
Sun...W Winds Up To 10 Kt.
Sun Night...N Winds Around 5 Kt.
Mon...W Winds Up To 10 Kt.
Tue...W Winds 5 To 15 Kt.
SHARE THIS PAGE:           
850 AM PDT Fri Sep 25 2020
Synopsis for the Central California Coast and Bays Including the Monterey Bay, Greater Farallones and Cordell Bank National Marine Sanctuaries - PZZ500
High pressure will strengthen off the California coast resulting in increasing northwest winds that will last through Saturday night. A larger long period northwest swell will continue through Friday with swell heights of 10 to 13 feet at periods of 13 to 15 seconds. Locally larger swell due to stronger winds are possible, especially along the Big Sur coast. Swell heights are expected to diminish tonight.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
1053am PDT Fri September 25 2020

Quiet weather to wind out the work week with sunny skies and seasonable temperatures. Noted warming trend starts by Saturday afternoon as offshore winds begin to develop. Offshore winds increase Saturday night into Sunday morning with Red Flag Warnings now in effect for the North and East Bay hills for critical fire weather conditions. Winds will ease on Sunday but hot and dry weather across the region. A second burst of offshore winds Sunday night into Monday morning with very warm and dry air in place. Continued unseasonably hot and dry Monday and Tuesday with only gradual cooling by midweek. West coast ridge stays in place through early October with no rain in sight for the Bay Area.

as of 08:08am PDT Friday...Morning temps across the CWA ranged in the 50s F and low 60s F as patchy clouds have already started to taper off over the SF Peninsula. Patchy clouds along the coast and some more cloud development along the East Bay is expected through the rest of the morning, but like yesterday expect for skies to clear up by early-to-mid afternoon. Another FROPA is expected over the PAC NW today but will not be seeing any immediate impacts from it in our CWA. Do also expect for onshore winds to pick up again today, keeping the coast in the 70s F and the interior in the 80s F. These conditions will make for a comfortable end to the work week before this weekend's setup gets going.

clouds along the coast again Saturday morning as we wait for offshore winds to develop. That should start to happen throughout the day Saturday allowing for some inland warming. Favorable north winds should start to reach the North and East Bay later Saturday afternoon as highs warm into the upper 80s and lower 90s with humidities lowering as dry north winds begin to develop.

Have upgraded the Fire Wx Watch to a Red Flag Warning, set to start at 9 pm Saturday night for the North and East Bay hills as well as the East Bay interior valleys. The 00z/06z NAM runs have trended slightly stronger with widespread 925 mb winds pegged at 40 kt. As is usually the case these winds will first show up across the Napa hills sometime around 9-10 pm Saturday night. Humidity values will start out fairly moist, above 30% but drying will persist all night. Please note most locations below 2000 feet will feel little or no wind Saturday night but the winds aloft will be blowing strong and acting to dry the airmass out. By Sunday morning the dry air will really be filtering into the Bay Area as north winds come down the Sac valley and spill into the Bay Area. Expect no fog Sunday morning, except perhaps from Monterey southward. The offshore winds will keep drying things out Sunday as temps soar into the 90s and lower 100s.

The models have trended stronger with winds on Sunday night and by this time humidity values will be in the teens, almost regionwide. The main trough axis is now forecast farther westward over the Rockies. This is dropping a little more cool air into the Great Basin but more importantly giving some upper support. In addition, the stronger surface pressure gradient is over the Sierra. And finally the 595 dm high to the northwest of Cape Mendocino will induce some subsidence aloft as well. Model cross sections now show north to northeast flow through much of the depth of the troposphere. To be clear this event is nowhere near the strength of the 2017 wine country, 2018 Camp or the 2019 Kincade fires. However the setup is still critical. In fact by Sunday night with the main surface gradient over the Sierra we will get a pure east wind event. Though not forecast explicitly by the models as east winds come off the Sierra they will make a beeline towards Mt Diablo and the North Bay. Again there will be no humidity recovery Sunday night and the models show east winds driving all the way to the coast and offshore. The setup is lacking cold advection but this is the type of pattern where we can see winds mix down into the I-880 corridor/Berkeley hills by Monday morning as well as to the lee of Mt Tamalpais with coastal gaps such as Hwy 92 to Half Moon Bay seeing locally strong east winds as well. All that to say the Red Flag Warning goes through 8 am Monday.

Beyond that an atypical late season ridge stays in place Monday through at least the middle of next week with temps staying well above normal. Will need to consider at least some possible Heat Advisories as the event gets closer. However, still believe the valleys and populated locations will see decent night time cooling while the hills will stay warm in the 70s and lower 80s at night.

Long range models show a very stable pattern with West Coast ridge in place all of next week as it bulges northward into British Columbia. Main trough axis over the Upper Midwest and over the Aleutians suggests little or no chance of rain through the first week of October as temps stay well above normal. Of course from late Sept through Columbus Day is often a time for offshore winds and no rain. of 4:00pm PDT Thursday...A deep low in the Gulf of Alaska has produced a large long-period swell train that will impact the coastline through tomorrow afternoon. Swells by this afternoon 10 to 12 ft with a 15 to 16 second period. The main impacts will be increased wave heigheights breaking near the shoreline and an increased risk of rip currents developing along coastal beaches. This may produce breaking wave heigheights in the surf zone of 15 to 20 feet, particularly at west to northwest facing beaches. Therefore, a Beach Hazards Statement has been issued from 5pm PDT this afternoon until 2pm PDT Friday. With the increase in temperatures inland expected late in the week, beachgoers should be mindful of the increased wave activity and rip currents.The wave activity is forecast to subside into Friday evening.

.CLIMATE...Here are the record high temperatures for Saturday through Monday... ......................SATURDAY.........SUNDAY..........MONDAY SANTA ROSA...........103 in 2009....103 in 2010.....104 in 2010 KENTFIELD............ 99 in 2016....103 in 1921.....102 in 1921 NAPA.................105 in 1963....101 in 1958.....102 in 1966 RICHMOND..............97 in 2019.....97 in 2010......97 in 2010 LIVERMORE............103 in 1952....105 in 1963.....105 in 2010 SAN FRANCISCO.........94 in 1992.....93 in 2010......95 in 1966 SF AIRPORT............95 in 1958.....96 in 2010......95 in 2010 REDWOOD CITY..........99 in 1963.....97 in 2010......98 in 2010 HALF MOON BAY.........90 in 1970.....89 in 1966......91 in 1958 OAKLAND DOWNTOWN......93 in 2016.....95 in 1973......92 in 2010 SAN JOSE..............98 in 2016.....98 in 1921......99 in 2010 GILROY...............104 in 1963....108 in 1963.....101 in 1963 SANTA CRUZ...........101 in 1970....103 in 2010.....100 in 1917 SALINAS..............101 in 2016....102 in 2010..... 99 in 1970 KING CITY............105 in 1963....107 in 2010.....102 in 1973

as of 10:47am PDT Friday...High pressure will strengthen off the California coast resulting in increasing northwest winds that will last through Saturday night. A larger long period northwest swell will continue through Friday with swell heigheights of 10 to 13 feet at periods of 13 to 15 seconds. Locally larger swell due to stronger winds are possible, especially along the Big Sur coast. Swell heigheights are expected to diminish tonight.

.MTR WATCHES/WARNINGS/ADVISORIES... .Tday...High Surf Advisory...CAZ530 SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm SCA...Pigeon Pt to Pt Pinos 0-10 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...Mry Bay from 3 PM