047 FXUS66 KMTR 110421 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 921 PM PDT Wed Oct 10 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 9:20 PM PDT Wednesday...An upper level vort center moved through the area today mixing out the marine layer. Inland temperatures were 8 to 13 degrees cooler than yesterday and better rh recoveries are being seen in the North and East Bay Hills. Low clouds have scattered out this afternoon and evening but should reform later tonight at a lower level as the marine layer becomes reorganized. The vort max that passed through today will form into a cutoff low over southern California on Thursday while upper level high builds off the Pacific Northwest. A warming trend will begin Thursday and continue through the weekend. Winds aloft will switch to the northeast so another round of offshore winds is expected in the mountains. Winds Thursday night and Friday morning will be stronger with gusts up to 30-35 mph in Napa and eastern Sonoma Counties and 20-25 mph in the other North Bay Mountains and East Bay Hills. Winds will decrease Friday night as the low moves away but may increase again Saturday night and Sunday morning as another inside slider drops into the Great Basin. Winds over the Santa Cruz Mountains and the Santa Lucias will also be offshore but wind speeds will be light. It looks like winds will not be strong enough nor will RH values be low enough for any wind or fire weather advisories. RH values will decrease towards the weekend as the persistant offshore flow dries out the airmass. Inland temperatures are likely to warm back into the 80s Friday through Sunday while 70s will be common near the coast. Low clouds will also be less widespread Thursday night through the weekend given the pattern in place. Medium range models show a rex block keeping dry weather over the area for next week. && .AVIATION...as of 04:29 PM Wednesday...For 00z tafs. Satellite imagery showing patchy stratus over the waters and along the coast. Expecting similar conditions tonight as was seen overnight yesterday. IFR to MVFR cigs tonight through late tomorrow morning for most sites with the exception of KLVK and KSJC. Onshore winds will diminish overnight before increasing again tomorrow afternoon. Vicinity of KSFO...VFR prevailing. Brief MVFR cigs possible around sunrise tomorrow morning. Winds to diminish overnight turning onshore and increasing to around 15 kt tomorrow afternoon. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR. Early return of IFR/MVFR cigs, as early as 02z. IFR/MVFR cigs expected through mid to late tomorrow morning. && .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 02:16 PM 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: W Pi AVIATION: AS 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