299 FXUS66 KMTR 161049 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 349 AM PDT Sun Oct 16 2022 .SYNOPSIS...A deep marine layer brings widespread cool temperatures and low clouds Sunday. Warming trend begins Monday and continues through midweek, before moderating at the end of the week. Dry conditions continue through the week. && .DISCUSSION...as of 03:49 AM PDT Sunday...Night satellite imagery shows widespread stratus once again, reaching into higher terrain as well. Coastal profilers earlier this afternoon were reporting a marine layer depth around 2500 feet, before they stopped reporting. A look at the 00Z KOAK sounding from this evening shows an inversion layer around 2700 feet. Cloud bases are being reported mostly around 2000 feet from surface stations. As a result of the higher bases, not seeing reports of fog or low visibilities. There has also been some warming at the surface, with most sites reporting temperatures in the upper 50s to low 60s, around 4 to 7 degrees warmer than 24 hours ago. The exception to this trend is the higher elevations in the hills, which are now several degrees cooler from the marine layer influence. Stratus will take a while to erode today, given the deep marine layer, and coastal areas may once again have a mostly cloudy day. While interior areas see clearing by afternoon, temperatures will be cool and below normal area-wide. The warmest interior locales may only reach the mid 70s, while along the coast 60s will be prevalent. Thus, similar temperatures to yesterday, or slightly cooler. The cooling trend is a result of the upper level ridge that was situated over the eastern Pacific being pushed inland by an upstream trough, now several hundred miles offshore. The leading edge of this trough is observed on water vapor imagery. As it approaches the coast this afternoon, we can expect increasing high level clouds. These clouds, along with an invading cooler airmass, will help moderate surface temperatures. The incoming trough and cool air advection may help to partly disrupt the marine layer tonight, though ensembles and hi-res models still show stratus re-forming. Thus, expect another night of low clouds with some patchy fog possible. The incoming trough is projected to stall before reaching the West Coast, and spawn a cut-off low, which will meander off the SoCal coast through much of the week. Meanwhile, the aforementioned upper level ridge will expand over the Intermountain West, leading to a warming trend over much of CA through midweek. Temperatures will likely be 5 to 15 degrees above normal by Wednesday, before moderating by the end of the week. Thus, expect 70s at the coast and 80s inland, perhaps low 90s in the warmest spots Wednesday. Global models are still projecting a trough moving down the coast next weekend along with some moisture. But it seems unlikely that it will dig deep enough to reach the Bay Area, as most ensemble members keep the area dry. The Euro still seems to be the most aggressive model for precip, but even that is not too promising. && .AVIATION...As of 10:31 PM Saturday...The arrival of a weak cold frontal boundary has brought stratus already to terminals and lifted cigs to between 1500 and 2500 feet. Other than slight variations in cig levels, no expectation for dramatic changes. Therefore high confidence for MVFR conditions forecast through the evening. Southerly winds have returned to KSJC earlier than forecast, but those will remain through the night. With continued weak onshore flow through the night, no mechanism to get rid of the clouds early. Therefore expect late clearing of clouds after 18Z at many terminals. VFR Sunday afternoon with an onshore seabreeze. Further intrusion of the cold front provides chance for VFR through the end of the TAF for many terminals. However, the models are keeping MVFR cigs in place for terminals in the North Bay and the Monterey Bay. Vicinity of SFO...High confidence of MVFR conditions through the night with breezy onshore winds. Moderate confidence in clearing late at the terminal, around 19Z, for VFR Sunday. Chance for lower cigs Sunday night, but stronger confidence at the current moment for cigs to develop above 3000 feet for VFR through the end of the TAF period. KSFO Bridge Approach...cigs over 1500 feet prevail through the night, not clearing until after 19Z, otherwise similar to SFO. Monterey Bay...MVFR. Another late clearing event. 18Z inland, with coastal terminals possibly holding on through 20Z. VFR and breezy onshore winds Sunday afternoon. There is a chance for clearer VFR skies Sunday night, but kept a return of MVFR cigs in the TAF currently. Will re-evaluate and remove if stronger confidence in staying VFR is determined. && .MARINE...as of 02:32 AM PDT Sunday...Light southwesterly winds will become occasionally breezy Sunday afternoon. Mixed northwesterly and southerly seas prevail. Winds become northwesterly next week, with the chance for stronger gusts along the immediate coast. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...None. $$ PUBLIC FORECAST: Lorber 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