Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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353 FXUS66 KMTR 011811 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1111 AM PDT Sat Jun 1 2024 ...New AVIATION... .SYNOPSIS... Issued at 255 AM PDT Sat Jun 1 2024 Cooler conditions today with temperatures near seasonal averages across most of the region. Warmer to hotter temperatures return Tuesday with moderate HeatRisk through the interior. && .UPDATE... Issued at 906 AM PDT Sat Jun 1 2024 Morning stratus is beginning to mix out across the northern SF Bay, the western San Mateo Peninsula, and across the Central Coast, down the Salinas Valley, and into the Gilroy-Hollister area. The marine layer has stabilized around 1200 feet at Bodega Bay and 2000 feet at Fort Ord, and stronger onshore gradients are contributing to some breezy winds across the region. The forecast remains on track with no changes at this time. Main concern continues to be the upcoming heat event beginning next Tuesday, which is expanded on in the previous discussion. DialH && .SHORT TERM... (Today and tonight) Issued at 431 AM PDT Sat Jun 1 2024 Coastal stratus and mist continue to develop due to a combination of surface to near surface cool air advection and nocturnal radiative cooling. The marine layer depth varies from 1200 feet at Bodega Bay to 2000 feet at Fort Ord. Northwest and southeast winds are juxtaposed along the coastline and inland, the northerly ACV-SFO pressure gradient is 4.9 mb, the SMX-SFO and SNS-SJC southerly pressure gradients are 1.6 mb and 2.1 mb respectively. Stratus and mist will continue developing through about sunrise then begin to mix out under diurnal surface warming as well as due to a strengthening and gusty northerly wind overlapping the immediate coastline later on today. Daytime highs today will be cooler most locations except the North Bay where downsloping winds will offset cooling. Highs today 60s/70s coastside and bayside, inland highs in the 80s. Coastal stratus redeveloping tonight and Sunday morning, lows cooling back to the upper 40s and 50s. && .LONG TERM... (Sunday through Friday) Issued at 431 AM PDT Sat Jun 1 2024 Night and morning stratus likely mixing out back to near the coastline Sunday afternoon and possibly again Monday afternoon. By late Sunday and Monday increasing amounts of water vapor will move across our forecast area, per comparison with Oakland upper air early June climatology precipitable water will reach the max moving average and may briefly exceed the early June daily maximum. Water vapor in contact with chilly sea surface temperatures favors stratus and we may also see light coastal drizzle. Beginning Tuesday the weather will then become quickly influenced by the strengthening of the subtropical high pressure system over the Pacific. The high will strengthen while sandwiched between a strong late season mid-latitude storm track reaching southwestern Canada and the Pacific NW (with a soaking rain) and the seasonally northward nudged Intertropical Convergence Zone well to our south. Global models are in better agreement with the overall motion of next week`s high pressure system, though there is some difference in the strength of the high. 850 mb temps (helpful for forecasting surface temperatures via dry adiabatic compressional warming of air parcels to the surface) vary by a couple degrees Celsius, these values are forecast to near the early June max moving average, possibly exceeding the daily maximum if the ECMWF verifies. Expect warm to hot daytime temperatures at least during Tuesday through Thursday, it`ll be hottest inland with 90s to lower 100s. At the coast there may be lingering sea-breezes though the marine layer will likely get compressed to 1000 feet or even lower, still tough to say with certainty since this is still a few days out, and the warm season maritime vs land temperature contrasts naturally keeps a thermally direct circulation potential in place. Another item to watch for, the meso to synoptic pattern may favor a southerly wind reversal either late Wednesday or Thursday. The PDO is still in a negative (cool phase). Hottest daytime temperatures this week look to be Tuesday-Wednesday with carryover into Thursday, and if the high pressure system becomes stationary then hot temperatures will carry into late week before sea breeze relief reaches inland. Though again, the global models do show potential for a southerly wind reversal i.e. sea breeze before late week. Lots of factors in the forecast next week, please stay tuned to updates. For the time being it`s a good idea to plan on at least moderate heat risk inland in our forecast area beginning Tuesday next week. && .AVIATION... (18Z TAFS) Issued at 1037 AM PDT Sat Jun 1 2024 Stratus continues to erode across the area with widespread VFR conditions expected this afternoon through the evening. Breezy to gusty winds build this afternoon with gusts generally in the 20-25 knot range. The immediate coast and KSFO are likely to see greater than 30 kt gusts. These stronger winds appear to last well into the overnight hours, but will ease in the morning. Winds aloft stay strong and more northerly overnight, leading to LLWS concerns. Stratus returns to the coast and the Monterey Bay terminals in the early night, and around the SF Bay into early Sunday. Breezy winds and widespread VFR return Sunday afternoon. Vicinity of SFO...VFR through early Sunday morning. Expect westerly winds to strengthen into the afternoon, gusting upwards of 35 knots. Winds reduce into the night but remain breezy until early Sunday morning as MVFR CIGs fill over the terminal. VFR and breezy winds are expected to return in the mid to late morning on Sunday. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Stratus lingers at MRY and along the coast of Monterey bay. VFR returns in the afternoon as winds increase and gust around 20-25 knots. Surface winds look to reduce into the late evening and early night with MVFR CIGs beginning to move inland. However, winds aloft will stay stronger, leading to some LLWS concerns and could delay cloud cover from filling over terminals. Winds aloft reduce in the late night/ early Sunday, with IFR CIGS starting to form around that time. && .MARINE... (Today through Wednesday) Issued at 849 AM PDT Fri May 31 2024 Breezy to gusty northwest winds will continue over the outer waters into the weekend with gale force winds expected late Friday and into Saturday. This will cause a hazardous marine environment. Significant wave heights will reach up to about 11-12 feet Friday afternoon, but will begin to reduce today through the remainder of the weekend. && .CLIMATE... Issued at 127 AM PDT Sat Jun 1 2024 Record high temperatures at the long term climate stations for June 4th and 5th: Station June 4th June 5th Santa Rosa 98 in 1949 102 in 1926 Kentfield 101 in 1981 102 in 1926 Napa 102 in 1981 105 in 1903 Richmond 90 in 1955 86 in 1983 Livermore 105 in 1960 104 in 1926 San Francisco 92 in 1949 95 in 1883 SFO Airport 92 in 1955, 1949 89 in 1972 Redwood City 100 in 1981 97 in 2002, 1972 Half Moon Bay 71 in 1955 74 in 1958 Oakland downtown 96 in 1981 87 in 2002 San Jose 98 in 1904 100 in 1926 Salinas Airport 92 in 1949 87 in 1949 King City 102 in 1981, 1957 105 in 1926 && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for SF Bay N of Bay Bridge. Small Craft Advisory until 3 AM PDT Sunday for Mry Bay. Gale Warning until 3 AM PDT Sunday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 PM PDT this afternoon for Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning from 3 PM this afternoon to 3 AM PDT Sunday for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 PM PDT Sunday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Canepa LONG TERM....Canepa AVIATION...Murdock MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea