378 FXUS66 KMTR 130503 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1003 PM PDT Thu Jun 12 2025 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 139 PM PDT Thu Jun 12 2025 Daily coastal stratus, breezy afternoon onshore winds, and interior highs in the 70s to 80s and low 90s across the far interior continue through this weekend. Dry conditions persist for elevated terrain above the marine layer leading to some fire concerns as grasses and smaller plants continue to cure. && .SHORT TERM... (This evening through Friday) Issued at 139 PM PDT Thu Jun 12 2025 The steady trend of coastal stratus in the morning, clearing for a few hours in the afternoon, and returning again during the evening continues Friday. The marine layer remains around 2000 ft and is expected to stay at that depth with no major changes to our zonal synoptic pattern in the short term. Areal stratus coverage has dissipated over the past few days with stratus coverage expected to continue diminishing across the North Bay and interior Bay Area tonight. The highest likelihood is stratus persisting along the coastline and into portions of the SF Bay shoreline. High temperatures are set to be in the 70s to mid 80s on Friday with the far interior Central Coast peaking in the low to mid 90s. Gusty onshore winds return this afternoon and again tomorrow afternoon with the strongest gusts expected across mountain gaps/passes, across the elevated terrain, and along portions of the coastline. Highest confidence is in gusts peaking between 30 to 35 mph but stronger gusts may develop along the highest peaks and in areas where funneling is favored (such as the Altamont Pass). With that in mind, an increased risk of grass fires exists across the higher elevations above the current marine layer depth (~2000 ft). This is particularly true for the North Bay Interior Mountains, East/South Bay Hills, and interior Monterey/San Benito Counties. Across the North Bay Interior Mountains and East/South Bay Hills, daytime humidity values are dropping into the 25-35% range. Daytime humidity values drop further in the interior Central Coast with values dropping into the 12-20% range. Larger fuels are still decently moist but are in the process of drying out. In the past few days the Dino Fire (Santa Clara) and Little Fire (San Benito) have been observed in dry, flashy small (grass) fuels and serve as a reminder that summer is here. For those living in the higher elevations, take precautions if utilizing an outdoors stove or campfire and follow all local guidance. && .LONG TERM... (Friday night through next Wednesday) Issued at 139 PM PDT Thu Jun 12 2025 The general pattern of more zonal flow and ridging to our east over the Intermountain West will help to keep our overall forecast steady through this weekend. High temperatures will generally stay in the upper 70s to mid 80s across the interior Bay Area and in the 90s across the interior Central Coast. Closer to the coastline temperatures will be cooler in the upper 50s to mid 60s. The marine layer looks to hold steady, if possibly compress slightly, around 2000 ft with daily coastal stratus to continue through this weekend. The pattern becomes a bit more uncertain Monday into early next week when a weak shortwave trough moves looks to move through the Bay Area. This trough is likely to allow the marine layer to deepen and for stratus to spread further into the Bay Area and Central Coast. This will help to keep temperatures cooler on Monday (highs in the upper 70s to low 80s across the interior) before a slight warming trend begins Tuesday. Interior temperatures will rise into the mid to upper 80s on Tuesday and mid 80s to low 90s on Wednesday. The warmest portions of the interior Central Coast will reach the mid 90s to low 100s on Wednesday. Gusty winds across the elevated terrain, gaps/passes, and along the coast will continue into next week along with drier daytime conditions across the interior. Modest improvements in daytime humidity values are expected across the interior Bay Area over the weekend but dry conditions across interior Monterey and San Benito Counties will persist into next week. && .AVIATION... (06Z TAFS) Issued at 1002 PM PDT Thu Jun 12 2025 Currently a mixed bag of VFR-MVFR at the terminals. Widespread VFR is expected by the afternoon with the exception of HAF. The pattern continues to be largely unchanged, as such a very similar forecast on tap. The marine layer is currently being observed at 1,500 feet and compressing; as such, ceilings that do develop will be low-end MVFR to high-end IFR. Low level wind shear is anticipated again tonight and tomorrow night, particularly in the North Bay, as the atmosphere decouples - generally expect light southwesterly winds at the surface with strong northwesterly winds aloft. Vicinity of SFO...Currently VFR with westerly flow. HREF and NBM both tack a 60% probability of sub-VFR ceilings developing overnight with high confidence in VFR by the afternoon. Westerly winds will prevail through the TAF period with gusts up to 30 knots to be expected. SFO Bridge Approach...Clouds below FL040 will begin to filter in by 09Z, with moderate to high confidence in them dissipating by 17Z. Monterey Bay Terminals...Currently MVFR with southwesterly flow at MRY and VFR with northwesterly flow at SNS. SNS will deteriorate to sub-VFR conditions shortly as stratus is being shown within the vicinity of the terminal. VFR and westerly winds will prevail by tomorrow afternoon. && .MARINE... (Tonight through next Wednesday) Issued at 1002 PM PDT Thu Jun 12 2025 Fresh to strong northwesterly breezes, near gale force gusts, and moderate to rough seas will prevail through Monday. Expect gale force gusts to develop near the coastal jet regions of Point Reyes and Point Sur during the afternoon and evening hours. && .FIRE WEATHER... Issued at 252 AM PDT Wed Jun 12 2025 Areas not being reached by the marine layer continue to see dry conditions. Higher elevations, particularly in the Santa Lucias and in the Gabilan range, continue to see poor humidity retentions and recoveries. In fact, some locations are hitting single digit and lower teens for RH values. A few locations in the interior North Bay are seeing breezy north to northeast winds and these winds look to last into the morning which will increase drying in these areas. Winds will remain breezy each afternoon/evening through the Delta, and any inland gap or pass. The combination of dry fine fuels (grasses), lower RH, breezy winds with gusts in the 20-40 mph will elevate fire weather concerns. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 9 AM to 9 PM PDT Friday for Mry Bay. Small Craft Advisory until 3 AM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm. Gale Warning until 3 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...Sarment MARINE...Sarment Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea