198 FXUS66 KMTR 202101 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 201 PM PDT Mon Oct 20 2025 ...New MARINE, BEACHES... .KEY MESSAGES... Updated at 1249 AM PDT Mon Oct 20 2025 - Warm and dry weather through Tuesday. - Less than 15% chance of thunderstorms across Central Coast Tuesday night into Wednesday. - Beneficial rain returns Friday through Sunday. && .SHORT TERM... Issued at 1249 AM PDT Mon Oct 20 2025 (Today and tonight) Another quiet fall day is on tap, with the main forecast highlight being another round of offshore winds developing tonight and continuing into Monday. Observations already show north to east winds over the North Bay region, while areas south have onshore flow. Expect offshore winds to continue to materialize overnight and linger into Monday. These winds will also usher in drier air to the region, which should keep much of the area stays free. The exception might be around Monterey Bay, as an otter eddy formed earlier in the evening and circulated some log clouds around it. Stratus may continue to do this dance overnight, teasing coastal Monterey County and the northern Salinas Valley with low clouds and patchy fog through the morning. Once the sun comes out, skies should clear and high temperatures will be beautiful, with 70s near the coast and 80s inland. Monday night into Tuesday, a southerly surge of stratus returns and creeps up the coast. Expect the marine layer to be around 500 feet bringing cool, cloudy, and foggy conditions for coastal communities. && .LONG TERM... Issued at 1249 AM PDT Mon Oct 20 2025 (Tuesday through Sunday) The extended forecast continues to remain interesting as models and ensembles show a cut off low that has been meandering off the coast of southern CA moving slightly to the north and then inland. One thing we know for certain with this system is that cooler temperatures will be ushered into the region, and the marine layer should deepen to around 1200 feet or so. Stratus should form along the coast and perhaps seep into some interior valleys. Where uncertainty lies with this system is the threat for thunderstorms. Deterministic guidance and some ensembles show the chance for isolated thunderstorm activity starting late Tuesday evening across portions of the Central Coast into Wednesday. As daytime heating allows, some guidance adds the threat of isolated thunderstorms along the higher areas of terrain for the East and South Bay counties. A fair amount of convective ingredients are available, mid level lapse rates around 7-7.5C/km, a couple hundred J/kg of MUCAPE, PWATs near 0.80", and lift from the low. The limiting factor seems to be shear at this point. For now, no mention of thunderstorms have been added into the forecast. Chances look to be around 14% or less, but that could change as we get more into CAM territory. Thankfully we have had some decent rain in the past, so fire weather concerns are low. After a cool Wednesday, we will see an uptick in high temperatures as weak ridging noses into the region on Thursday. An area of low pressure off the Gulf of Alaska will deepen, allowing for upper level troughing and zonal flow to take over. At this time it looks like beneficial rain appears to be the most likely solution as ensembles continue to trend towards lower amounts Friday - Sunday. Right rainfall amounts look like this: North Bay counties may see around 0.50-1.25", East Bay counties, Santa Cruz County, and the San Francisco Peninsula around 0.15-0.50", Santa Clara 0.10-0.40", and finally Monterey and San Benitio counties 0-0.15". These amounts will likely change, so stay tuned to the forecast. && .AVIATION... (18Z TAFS) Issued at 1038 AM PDT Mon Oct 20 2025 VFR conditions have returned to most terminals as of midmorning, the exception being KHAF where visibilities are below 3SM. Expecting VFR conditions to prevail through much of the TAF period with moderate confidence for low ceilings and/or visibilities to return to the Monterey Bay terminals and KHAF early Tuesday morning. Vicinity of SFO...High confidence for VFR through the TAF period. Onshore winds will increase slightly this afternoon or early evening before becoming light and variable overnight into Tuesday morning. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...High confidence for VFR through early in the TAF period. Onshore winds increase a bit this afternoon before becoming variable at KMRY and southerly at KSNS early Tuesday morning. There is also moderate confidence for low ceilings and/or fog to develop early Tuesday morning as a southerly surge impacts the region with a marine layer around 500 feet in depth. && .MARINE... (Tonight through next Saturday) Issued at 200 PM PDT Mon Oct 20 2025 Moderate to fresh northwesterly winds will steadily diminish through Tuesday, allowing the seas to gradually subside before a new long period northwest swell arrives early Tuesday night and again on Thursday night. Wet weather conditions return by Friday and continue into the upcoming weekend as a storm system approaches from the north. && .BEACHES... Issued at 200 PM PDT Mon Oct 20 2025 The Beach Hazards Statement has been extended out in time through 9 PM Wednesday as a moderate to long period northwesterly swell impacts all of the Bay Area and Central Coast beaches. These conditions will result in breaking waves of 15 to 20 feet and up to or exceeding 25 feet at favored break points such as Mavericks. Never turn your back to the ocean! Swim near a lifeguard if possible! If caught in a rip current, swim parallel to shore until you escape its influence. RGass && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Wednesday evening for CAZ006-505- 509-529-530. PZ...Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 9 PM Tuesday to 9 AM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 3 AM to 9 AM PDT Wednesday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ SHORT TERM...KR LONG TERM....KR AVIATION...RGass MARINE...RGass 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