Point Arena to Pigeon Point between 60 and 150 NM Offshore Forecast
|Tonight...W To Nw Winds 5 To 15 Kt, Becoming 5 To 10 Kt. Seas 5 To 6 Ft.|
|Wed...W To Sw Winds 5 To 15 Kt. Seas 4 To 6 Ft.|
|Wed Night...W To Sw Winds 10 To 15 Kt. Seas 6 To 10 Ft.|
|Thu...W To Nw Winds 5 To 10 Kt, Becoming N 5 To 15 Kt. Seas 8 To 14 Ft.|
|Thu Night...Nw Winds 10 To 15 Kt, Becoming 10 To 20 Kt. Seas 12 To 14 Ft.|
|Fri...Nw Winds 10 To 20 Kt. Seas 11 To 13 Ft.|
|Fri Night...Nw Winds 15 To 25 Kt, Becoming N. Seas 9 To 12 Ft.|
|Sat...N Winds 15 To 25 Kt. Seas 8 To 11 Ft.|
|Sat Night...N Winds 20 To 25 Kt. Seas 8 To 11 Ft.|
|Sun...N Winds 15 To 25 Kt. Seas 8 To 10 Ft.|
|Sun Night...N Winds 15 To 25 Kt. Seas 8 To 10 Ft.|
| 234 PM PDT Tue Sep 22 2020 |
Synopsis for the Central California Coast and Bays Including the Monterey Bay, Greater Farallones and Cordell Bank National Marine Sanctuaries - PZZ500
Light to locally moderate northwest winds today, strongest along the inner coastal waters where hazardous conditions for small craft vessels may exist. The first larger height, longer period northwest swell of the season will arrive Thursday and Friday with heights generally around 10 to 12 feet and periods of 16 to 18 seconds.
| Area Forecast Discussion|
National Weather Service San Francisco Bay Area
525pm PDT Tuesday September 22 2020
.SYNOPSIS..A seasonable weather pattern on Wednesday with ridging aloft. A weak front moves into Northern California on Thursday but no rain for the Bay Area with just some increasing onshore winds and slight cooling of temps. Slight warming trend starts Friday then much warmer over the weekend with Sunday the hottest day. Offshore winds over the weekend with increased fire weather concerns and a Fire Weather Watch already posted for the North and East Bay hills this weekend. No sign of the ridge breaking down with above normal temperatures continuing at least through the middle of next week.
as of 2:08pm PDT Tuesday...Skies are mostly sunny this afternoon across the Bay Area and most of the smoke from nearby fires has mercifully stayed out of the Bay Area. The marine layer is around 1200 feet with some patchy clouds from Ocean Beach down to Davenport. Farther south low clouds are lingering from Monterey Bay and down along the Big Sur coast. The SFO to Sac gradient is 2 mb onshore with a steady 20 mph wind at the Golden Gate keeping temps in the 60s for the City and along the coast.
Looking ahead to Weds expect to see some shortwave ridging from SoCal that will build heigheights to around 590 dm. However, persistent onshore winds will keep temperatures running near normal with 70s around the Bay and 80s inland with 90s for the hottest interior valleys of the Central Coast.
On Thursday a weak front moves into far Northern California. It may bring some light rain to fires up near the Oregon border. Locally it will help to deepen the marine layer with perhaps some drizzle for the coastal slopes and places like the Wallbridge and ward burn scars.
On Friday behind that front the flow across Oregon turns zonal as the main jet shifts north and high pressure quickly builds over the Bay Area as a 591 dm closed height field develops while the remnants of Tropical Storm Lowell drift well to our south and west. As this ridge builds temps will begin to rebound slightly by Friday afternoon which will augur the beginning of a significant warming trend this weekend.
Strong high pressure builds over the entire West Coast Saturday and Sunday. 850 mb temps around 24 celsius by Saturday afternoon warm to 27 celsius by Sunday afternoon as 500 mb heigheights climb to 595 dm. This all happens while an offshore surface pressure gradient develops. The strongest gradient will be over the Sierra with upper support only minimal as cold air is shunted well to our east. The upper pattern wont support strong winds. However a period of moderate offshore winds with gusts to 50 mph is currently forecast for Saturday night into Sunday morning, most focused over the North Bay hills.
A Fire Weather Watch has been posted from 11 am Saturday through 8 am Monday morning for the North and East Bay hills as well as the East Bay interior valleys. This is a longer lead time than normal but confidence is high that event will unfold though it could trend slightly stronger or weaker in terms of wind strength. The National Preparedness level is still at its highest level of 5 with numerous large fires continuing across the West that has kept fire fighting resources stretched thin. In addition to the typical offshore winds confidence is high for above average temperatures this weekend with widespread 90s to lower 100s. Sunday looks to be the hottest day. So by Saturday morning temps will be quickly warming as offshore winds start to develop in the hills then peak overnight Saturday into Sunday morning. There will essentially be no humidity recovery with values in the 10-20% range while fuels are of course critically dry as observed over the last month of burning. Current model projections show 925 mb winds to around 45 mph so gusts in the 50-55 mph range look likely at this time around Mt Saint Helena and Mt Diablo as well as Mt Tamalpais.
A second burst of winds could occur Sunday night into early Monday but that looks weaker at this time though there will continue to be no marine layer or humidity recovery.
Though offshore winds may ease early next week all indications for several more days of hot afternoons. Will have to look closer at heat advisory potential by Sunday or Monday but the dry airmass should allow for decent night time cooling of temps that will help with overall cumulative effect of heat impacts.
.BEACHES...as of 04:38am PDT Tuesday...A deep low in the Gulf of Alaska will produce a large long-period swell train that will arrive late Thursday evening and into Friday morning. Swells by then could be up to 9 to 11 ft with a 16 to 18 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. With the increase in temperatures inland expected this weekend, beachgoers should be mindful of the increased wave activity and rip currents. The wave activity is forecast to gradually decrease through the weekend, but caution is advised through at least Sunday morning.
as of 02:34pm PDT Tuesday...Light to locally moderate northwest winds today, strongest along the inner coastal waters where hazardous conditions for small craft vessels may exist. The first larger height, longer period northwest swell of the season will arrive Thursday and Friday with heigheights generally around 10 to 12 feet and periods of 16 to 18 seconds.
.MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm until 9 PM SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm