395 FXUS66 KMTR 211128 AAA AFDMTR Area Forecast Discussion...UPDATED National Weather Service San Francisco Bay Area 428 AM PDT Sat Aug 21 2021 .SYNOPSIS...Interior temperatures will continue on a cooling trend on Saturday as onshore flow increases. This pattern will also help to clear smoky and hazy conditions across the region through the weekend. Inland temperatures will begin to warm next week as high pressure builds over the Southwest. && .DISCUSSION...as of 04:25 AM PDT Saturday...The rapidly deepening marine layer and southwest flow within said boundary layer has resulted in patchy drizzle across the region this morning. Non- ASOS sites along the coast and even in the hills of the North Bay have reported 0.01" or so in the past few hours as a result. Thus, have updated the forecast this morning to including patchy drizzle. Precipitation may be enough to result in slick roadways this morning. && .PREV DISCUSSION...as of 02:55 AM PDT Saturday...A mid/upper level low descending into the Pacific Northwest this morning continues to promote an increase in onshore flow across the central California coast. As such, a well-defined marine layer of around 2,000 feet in depth has allowed for coastal stratus to spread well inland into the region. Temperatures are generally holding in the upper 50s to lower 60s as a result with good humidity recoveries in the hills. Above the marine inversion, slightly warmer and drier conditions prevail with generally light west to southwest winds. The increased onshore both at the surface and aloft will allow for slightly cooler conditions across the interior today. Additionally, this pattern is forecast to improve smoky/hazy conditions across the region today into Sunday. As the aforementioned mid/upper level low ejects eastward toward the northern Great Plains, broad troughing will still persist along much of the West Coast. This will keep temperatures at to near seasonal averages through the remainder of the weekend with slight warming across the interior. Forecast ensembles indicate the mid/upper level high over Texas will expand westward over the Southwest into next week. While onshore flow and the marine layer is likely to persist, this expanding high pressure will result in a warming trend for interior locations of the San Francisco Bay Area and Central Coast. Look for more widespread 80s and 90s for the region's warmer locations with even a few of the hot spots reaching or exceeding 100 deg F by late in the week. This said, not expecting any significant weather impacts at this time through next week. && .AVIATION...As of 11:57 PM PDT Friday...For the 06z TAFs. Wildfire smoke and haze causing reductions of slant range visibilities and locally surface visibilities to MVFR levels. The marine layer is well developed over the coastal waters and is ushering stratus and fog inland, the marine layer depth is 1600-1800 feet. Expect patchy light coastal drizzle through Saturday morning. Vicinity of KSFO...MVFR ceiling developing overnight, mixing out to VFR 17z-18z Saturday. Slant range and surface visibility reduced through the period, but should begin to improve Saturday afternoon once smoke clears over the coastal waters and onshore winds push smoke eastward. Light breezy conditions overnight, onshore wind to 15 knots Saturday. KSFO Bridge Approach...similar to KSFO. Monterey Bay...VLIFR-IFR tonight and Saturday morning. Still plenty of smoke and haze aloft and lesser amounts at the surface, with some reduction in both slant range and surface visibilities. CIGs lift and scatter late Saturday morning or early afternoon with improvements in vis expected by the afternoon. && .MARINE...as of 02:55 AM PDT Saturday...Gusty northwest winds continuing over the northern outer waters, lighter winds elsewhere. A long period southerly swell gradually diminishing through the weekend and a short period northwest swell will persist at about 9 to 11 seconds. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...SF Bay from 3 PM SCA...Pt Arena to Pt Reyes 0-10 nm from 3 PM && $$ PUBLIC FORECAST: RGass AVIATION: Canepa MARINE: Canepa 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