155 FXUS66 KMTR 102141 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 241 PM PDT Wed Oct 10 2018 .SYNOPSIS...Moist onshore flow will continue to result in seasonably cool weather conditions into Thursday. Weak offshore flow will then develop late in the week resulting in warmer and drier conditions regionwide through the weekend if not into next week as well. && .DISCUSSION...as of 02:40 PM PDT Wednesday...A moist south- southwest flow continues to result in cloud development along the Big Sur Coast and up across the Santa Cruz Mountains early this afternoon. However, most automated reporting sites are no longer reporting light precipitation. Elsewhere, temperatures are generally in the 60s and 70s region-wide in response to a broad mid/upper level trough across the West. Do expect low clouds to return overnight given the moist onshore flow, however will not be a typical setup given the deep, well-mixed marine layer. Temperatures warm by a few degrees on Thursday, yet still remain near to below seasonal averages. The forecast models are in good agreement regarding the upper level pattern set to develop over the region late in the week and into the upcoming weekend. Energy from the broad trough over the region is forecast to shift eastward and develop into an upper level low off of the southern California coast by Friday. Meanwhile, a ridge of high pressure over the eastern Pacific will build inland over the Pacific Northwest, thus forming a Rex-Block pattern. This will likely result in a gradual warming trend through the weekend with periods of weak offshore flow inland and in the higher elevations. At this time, the strongest winds appear to occur Thursday night into Friday morning with drying conditions, especially in the North Bay Mountains/Hills. Northerly winds with gusts of around 30 mph cannot be ruled out in the hills/mountains of Napa County, however widespread breezy to gusty conditions are not anticipated at this time. Winds weaken slightly Friday and remain weak through the weekend along with continued dry weather conditions. By Friday, inland temperatures are likely to warm back into the 80s while 70s will be common near the coast each afternoon. Overnight/morning cloud cover will also be less widespread through the weekend given the pattern in place. The upper level low that develops well to our south will push inland over southern California during the weekend and may produce light precipitation across that portion of the state while dry conditions persist over the San Francisco Bay Area and Central Coast. && .AVIATION...as of 11:00 AM Wednesday...Discontinuous patches of stratus across the North Bay and Monterey Bay late this morning, bringing local MVFR cigs to KSTS KMRY KSNS KWVI. Expect to see widespread VFR by 1830-1900Z as these cloud decks mix out. Light onshore winds will develop this afternoon generally 10 to 15kt. For tonight, another round of patchy IFR to MVFR cigs by sunrise thru mid to late morning. Vicinity of KSFO...VFR. Light northerly winds thru late morning then increasing and becoming more onshore by the afternoon. VFR through most the night with brief MVFR cigs possible around sunrise THU. Winds slightly stronger tomorrow afternoon. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR after 19Z. Light onshore winds today. Early return of borderline IFR/MVFR cigs as early as 02Z THU, persisting through mid to late morning THU. && .BEACHES...Tropical storm Sergio will bring moderate period and height swell to the Central California and Bay Area coastlines beginning Thursday morning. Exposed south facing beaches will be at highest risk for building surf. Some breakers may reach as high as 10 feet with 10 to 20 minute lulls between sets. All beaches will experience an increase in rip current activity during the second half of the week as this swell arrives and transits the area. Therefore, a Beach Hazards Statement has been issued from early Thursday morning through late Friday afternoon. && .MARINE...as of 10:52 AM PDT Wednesday...Split flow with lighter south to southwest winds along the coast and stronger gusty northwest winds over the northern outer waters. Mixed northwesterly and southerly swell will continue through the forecast period, southerly swell is originating from Tropical Storm Sergio. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 AM && $$ PUBLIC FORECAST: RGass AVIATION: DRP MARINE: DRP 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