FXUS66 KMTR 160533 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 933 PM PST Fri Jan 15 2021 .SYNOPSIS...A warming and drying trend will continue through the upcoming weekend as high pressure builds over the state. Dry weather with breezy offshore flow is expected Sunday through the middle of next week while temperatures begin a cooling trend Tuesday. && .DISCUSSION...as of 09:10 PM PST Friday...Another chamber of commerce weather day across the Bay Area and Central Coast with sunny skies and above normal temperatures. Temperatures were in the 60s and 70s with a few 80s sprinkled in there. Salinas set a new record of 84 degrees and Santa Rosa tied their old record of 70. High temperatures of this magnitude are 10-20 degrees above normal for mid January. High pressure that brought the mild temperatures today will slowly retreat and slide southwestward the next 12 hours. As this happens, high clouds will continue to spill in from the north. The high clouds overhead tonight will limit the cooling potential in the valleys. The hills will also remain on the mild side tonight given the clouds and slight offshore flow at 2500'. Some lingering low level moisture may result in some patchy fog in the North Bay Valleys, but conf is low. Tomorrow will be another mild day across the region as high pressure eases to the southwest a little. Temperatures may be a few cooler than Friday, but still above normal on Saturday. Temperatures will rebound on Sunday as high pressure noses northward again. Simply put, a nice weather weekend ahead. By Sunday evening the pleasant weather will come to an end. High pressure gets shunted to the southwest again as a shortwave trough drops in from the N and moves into SoCal. This will be the initial setup for an extended period of offshore flow. One metric for offshore flow in the Bay Area is the SFO-WMC pressure gradient. As the shortwave trough passes through, the offshore gradient ramps up -12 to -14 mb depending on model choice. This is enough to generate some breezy to gusty offshore winds over the higher terrain and foothills. Winds will be strongest over the North Bay Mts and East Bay Hills. A High Wind Watch is currently in effect for Sunday evening through Monday afternoon to capture this initial push. Night shift will likely upgrade the watch to an advisory. Winds slacken a little bit on Monday afternoon, but the bigger blast of wind looks to occur Monday night and Tuesday. As the shortwave trough exits to the south a much deeper upper low/trough dig into the Desert Southwest Monday night before ultimately becoming a cutoff low off SoCal by Wednesday. This secondary feature will really crank up the pressure gradient. The SFO-WMC gradient goes up to -19 to -22 mb! Additionally, the RDD- SAC gradient also gets up to 9 mb, which would result in stronger winds in the Central Vally and Delta region. This dramatic increase is just on today's model run so some caution should be used. However, confidence is moderate to high as other tools suggest stronger winds too. The ECMWF extreme forecast index shows the projected forecast is well above climo and several ensemble members support the outcome. The NAEFS guidance also shows a high probability of strong winds Monday night and Tuesday. Needless to say, a lot to fine tune between now and then but if models keep trending this way it could be a bigger wind event with high wind warnings needed. && .AVIATION...as of 09:33 PM PST Friday...For the 06Z TAFs. Mostly VFR through the TAF period. A chance for low clouds and fog remains in the TAFs for the North Bay Valleys; however, increasing high clouds is decreasing confidence. There is a break in the clouds up near Eureka which is moving southward which with lighter cloud cover could help with radiational cooling and patchy fog. Winds continue to subside. Low clouds are forecast to scatter after 18z for VFR Saturday. Winds will increase and be breezier, especially closer to the coast before weakening Saturday night as high clouds increase. Vicinity of KSFO...High clouds remain over the terminal, but still VFR. If the high clouds remain light, a slight chance for low clouds and reduced vis remain in the TAFs but it remains with low confidence. Winds remain light. VFR conditions expected through Saturday as onshore winds increase with a few stronger gusts before weakening Saturday night. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...A few breezier winds remain close to the coast, but conditions are expected to be VFR through the TAF period. Winds will diminish overnight before onshore and breezy Saturday afternoon. && .BEACHES...as of 08:46 PM PST Friday...A moderate, long period northwest swell will arrive along the coastline today resulting in hazardous conditions in the surf zone. Initial forerunners of 3 to 6 feet at 20 to 22 seconds will result in an increased risk of dangerous sneaker waves and rip currents today. As the swell builds through tonight and into Saturday, breaking waves of 15 to 17 feet (locally up to 20 feet at favored breakpoints) can be expected along west to northwest facing beaches. While these waves are not as large as our previous events in the most recent days, unseasonable warm temperatures this holiday weekend will likely attract more people to the coast. Individuals should be reminded that our coastline and the cold Pacific waters remain dangerous as these larger than normal waves impact the coast. Extreme caution is advised when visiting area beaches. Additionally, a second very long period and larger west to northwest swell will arrive on Sunday. Additional hazard products will likely be needed once the current ones expire. && .CLIMATE...Record Type: Highs (Old Record Temp/Year) Jan 15th Jan 16th Jan 17th Jan 18th Santa Rosa 70/2011 74/1991 71/1991 74/1976 Kentfield 68/2014 70/2009 71/1994 70/2014 Napa 72/2014 76/1920 72/1920 76/1920 Richmond 72/2009 74/2014 73/2009 71/2018 Livermore 75/1920 75/1920 70/1986 74/1919 San Francisco 73/2009 72/2014 73/1991 70/1920 SFO 73/2014 73/2014 70/1991 68/1948 Redwood City 78/2009* 74/2014 77/1948 74/2009 Half Moon Bay 75/2009 76/2014* 75/2009 72/2009 Oakland Downtown 76/2014 78/2014* 74/2014 73/2014 San Jose 73/2009 73/2014 76/1920 74/1920 Gilroy 73/2014 76/2014 77/2014 80/2014* Santa Cruz 83/2014 84/2014 83/2014 83/1920 Salinas Airport 83/2014 84/2014 86/2014* 81/1994 King City 82/2009 85/1976 86/2014* 83/2009 *Monthly Records && .MARINE...as of 08:46 PM PST Friday...A new moderate west to northwest swell builds tonight resulting in hazardous seas conditions for small crafts into the weekend. Winds are moderate to locally breezy and out of the northwest across the waters through much of the weekend. Winds will shift more northerly Sunday to Sunday night and increase as offshore winds pick up over land. Stronger winds will then persist into early next week. A second larger long period northwest swell will arrive late Sunday. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...High Surf Advisory...CAZ006-505-509-530 SCA...Mry Bay from 3 AM SCA...Pt Reyes to Pigeon Pt 0-10 nm from 3 AM SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 AM SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm && $$ PUBLIC FORECAST: MM AVIATION: DK MARINE: DK 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