639 FXUS66 KMTR 070448 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 948 PM PDT Sun Jul 6 2025 ...New AVIATION, MARINE... .KEY MESSAGES... Updated at 129 PM PDT Sun Jul 6 2025 - Moderate HeatRisk returns to portions of the Interior Bay Area and Central Coast Wednesday through next weekend. - Localized elevated fire weather conditions for the Bay Area and Central Coast Wednesday through next weekend. - Slight risk (20%-40%) of extreme heat for far interior portions of the Bay Area and Central Coast July 12th-14th. && .UPDATE... Issued at 715 PM PDT Sun Jul 6 2025 The marine layer stratus is beginning its nocturnal push inland as the sun begins to set. By morning, the coverage should be slightly more expansive than today as low pressure offshore allows the marine layer to deepen. Cool and moist will be the theme through Tuesday before a ridge builds and brings inland temperatures above normal Wed-Fri. Thursday looks like the warmest day, but with temperatures about 5 degrees above normal, we are only expecting moderate HeatRisk in inland and higher elevation areas within the North Bay, East Bay, South Bay and Monterey and San Benito Counties. A cooling trend should bring temps back to normal this weekend. && .SHORT TERM... Issued at 129 PM PDT Sun Jul 6 2025 (This evening through Tuesday) An upper-level cutoff low off the Northern California Coast will be the defining feature of the short term forecast. Sensible weather will feature seasonably cool conditions and onshore winds with gusts up to 35 mph through gaps and passes, across ridgelines, and down the Salinas Valley. The marine layer is currently being observed at 1,800 feet on the Fort Ord profiler and will continue to deepen to 3,000 feet by Tuesday. This, in addition to the stratus presentation currently, means that it will have no problem penetrating farther inland tonight and continuing that trend tomorrow night. There is also a slight (15%) chance for drizzle along the coast and over the waters due to the lifting mechanism in place. Southerly transport winds may (you guessed it) transport smoke in from the Madre Fire that is burning in San Luis Obispo through Tuesday. && .LONG TERM... Issued at 129 PM PDT Sun Jul 6 2025 (Wednesday through next Saturday) The pattern begins to change Wednesday as the upper-level cutoff low becomes an open wave and gets nudged eastward by building broad high pressure. This will kickoff the warming and drying trend with the return of moderate HeatRisk and localized elevated fire weather conditions. Fortunately, several rounds of upper-level shortwave trough energy will help keep the ridge in check, not allowing the axis or peak to enter our area. Global ensemble clusters are in agreement with heights rising through Thursday with the ridge showing signs of weakening, albeit slightly, Friday. This will translate to Thursday being the warmest day of the week with temperatures topping out at 10 degrees above normal with Friday being slightly cooler. Global ensemble clusters diverge Saturday with 51% in favor of heights rebuilding and 49% in favor of heights falling, suggesting uncertainty in the forecast. The propagation of what happens will be integral in the extended forecast as the Climate Prediction Center (CPC) has highlighted the far interior portions of the Bay Area and Central Coast with a slight (20%-40%) chance of extreme heat July 12th-14th, thus it is intuitive to believe that if the ridge has more time to build that we could be dealing with hotter conditions and subsequently greater impacts than what are currently being forecast. In terms of elevated fire weather conditions, high pressure and the accompanying subsidence aloft will compress the marine layer to 1,000 feet Wednesday resulting in little inland intrusion and poor to moderate relative humidity recovery above it. Additionally, light offshore flow is expected in the higher terrain during the morning hours of Wednesday and Thursday. Please exercise fire and heat safety, especially coming off of a cool June. && .AVIATION... (06Z TAFS) Issued at 937 PM PDT Sun Jul 6 2025 Marine layer holding steady around 1 kft going into the overnight hours, and will persist into the morning hours. Most terminals that get cigs overnight will likely see LIFR/IFR, and more likely to be teetering IFR/MVFR around the SF Bay. Reasonably good confidence in timing forecasts as clouds build in tonight, and high confidence that stratus will hold on to much of the immediate coastline through the day Monday. Breezy onshore flow during the afternoons, nothing out of the ordinary in terms of wind. Vicinity of SFO...Decent confidence in the timing of stratus affecting the vicinity of the terminal, but less confidence if persistent stratus will actually settle in over the airfield. Slightly shallower marine layer allowing for some drying as air descends the San Bruno Gap, so there is some uncertainty with how much the northern part of the Bay will fill in. Otherwise, high confidence in clearing time Monday morning, should cigs fill in over the terminal. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...LIFR/IFR overnight tonight with reasonable confidence in mid-morning clearing to VFR and mostly SKC throughout the rest of Monday. Marine stratus expected to return just after sunset. Earlier along the immediate coast. && .MARINE... (Tonight through next Saturday) Issued at 937 PM PDT Sun Jul 6 2025 Winds continue to diminish over the outer waters tonight. Gentle to moderate breezes persist across the coastal and outer waters through the middle of the week. Winds increase by the latter half of the week with moderate to fresh breezes expected. Building seas across the outer waters late in the week as a modest northwesterly swell enters the picture around 9 to 10 feet at 9 seconds. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...Behringer MARINE...Behringer Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea