531 FXUS66 KMTR 111206 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 504 AM PDT Thu Oct 11 2018 .SYNOPSIS...Moist onshore flow will 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 2:48 AM PDT Thursday...Satellite imagery shows a low clouds have spread inland from the coastal waters, covering a good portion of the CWA. Current temperatures are similar to those from yesterday at this time and are mostly in the 50s. Continued weak onshore flow will keep temperatures on the cool side today. By Friday, a weak offshore flow will set up resulting in some gusty breezes in the north Bay hills, and a bit of a warming trend that will extend into the weekend to early next week. By Sunday and Monday, warmest inland areas could see high temps around 90 degrees. Near-coastal areas are expected to warm to the upper 60s to mid 70s. Wind speeds will increase tonight and Friday morning with gusts up to 30-35 mph in the higher elevations of Napa and eastern Sonoma Counties and 20-25 mph in the other North Bay Mountains and East Bay Hills. Winds will decrease Friday night but may increase again Saturday night and Sunday morning as another disturbance moves into the Great Basin. Winds are not expected to be strong enough to prompt any wind or fire weather advisories, however, relative humidity values will lower during the weekend as the persistent offshore flow dries out the airmass. Dry weather to persist through the forecast period as a ridge of high pressure builds in over the west. && .AVIATION...as of 5:03 AM Thursday...It's VFR with areas MVFR ceilings, cool lower level temperatures eroded marine temperature inversions. A stationary north-south surface trough over the coastal waters is resulting in southerly flow advecting areas of low clouds northward, MVFR ceilings are overlapping the north Central Coast and Bay Area. 12z tafs carry previous forecasts of generally early mixing out of low clouds this morning. The NAM model shows the surface trough becoming replaced by a mainly weak surface high pressure ridge in the afternoon and evening, by about the same time a 500 mb low closes off near northern Monterey county, continuing to move W-SW Friday and Saturday. As best can tell from the NAM cross sections the 500 mb low will behave independent of the layer from 700 mb to the surface. Nonetheless plenty of mixing without a marine inversion returning today at least should keep VFR settled in for tonight. Vicinity of KSFO...Southerly flow 5-10 knots, tempo MVFR ceiling between 13z-15z. Otherwise VFR today, tonight and Friday. Wind becoming NW 10-12 knots by 21z today then shifting to NE 5-10 knots by 04z. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...MVFR ceilings with early clearing to VFR likely this morning. Light wind becoming NW 10 knots by late morning or early afternoon. Low confidence VFR holds this evening. && .BEACHES...Tropical storm Sergio will bring moderate period and height swell to the Central California and Bay Area coastlines beginning this 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 this morning through late Friday afternoon. && .MARINE...as of 2:28 AM PDT Thursday...Winds will be mainly light across the coastal waters into the weekend. The southerly swell generated by Tropical Storm Sergio will increase today into Friday before subsiding by evening. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...NONE. && $$ PUBLIC FORECAST: Sims AVIATION/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