


Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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513 FXUS66 KMTR 031714 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1014 AM PDT Thu Jul 3 2025 ...New AVIATION... .KEY MESSAGES... Updated at 950 AM PDT Thu Jul 3 2025 - Elevated fire weather concerns Thursday afternoon and evening for the East Bay and Santa Cruz Mountains. - Northwest winds of 30 to 55 mph Thursday afternoon and evening across gaps, passes, and some valleys. - Night and morning low clouds clearing to the coast each afternoon remains. - Near normal temperatures with slightly below normal temperatures Thursday and Friday. && .UPDATE... Issued at 950 AM PDT Thu Jul 3 2025 The inherited short term forecast is in good shape with only a few alterations to peak wind gusts. Onshore flow is anticipated to continue in earnest today with the SFO-SAC gradient of +3 to +5 mb. This is toward the higher end of the scale when it comes to anticipating, at least qualitatively, the magnitude of onshore winds. Short term model guidance in conjunction with higher end NBM wind probabilities appear to support anywhere from 35 to near 50 knot surface winds through some of the favored gaps, passes, and exposed NW to SE oriented valleys across the Bay Area and Central Coast. Specifically, areas near and down wind of the San Bruno Gap, Altamont Pass, and the Salinas Valley will be most prone to the strongest winds. As such, afternoon wind gust grids have been adjusted to match closer to the latest model guidance with gusts averaging between 30 and 55 mph in this regions. Because of the limited geographic extent, we aren`t anticipating any wind headlines. Fire weather concerns remain elevated due to the increased breezes. While onshore flow will keep afternoon humidity above critical thresholds, smaller/finer fuels such as the grasses and brush are cured, available and will support some fire spread if left unmonitored. In short, be mindful if handling an open flame, be sure to avoid parking on tall grass/vegetation, extinguish camp fires. Also, obey any local fire restrictions, burn bans, and/or firework regulations. && .SHORT TERM... Issued at 300 AM PDT Thu Jul 3 2025 (Today and tonight) Overnight satellite fog product shows a slightly different set up early Thursday morning compare to the last few nights. While we still have some marine layer clouds extending into the Salinas Valley, northern areas are seeing much less in the way of low clouds. A pocket of drier air near the surface, stronger N-S gradient, and passing high level clouds are all likely contributing to less clouds. Latest hi-res capture this rather well so portions of the North Bay, East Bay, and Bay Shoreline will likely see the sunrise unlike the last few mornings. Coastal San Mateo southward to Big Sur, including Monterey Bay region, will be cloudy. Decided to remove drizzle from the forecast as well based over observation and lastest model guidance. The bigger story for Thursday will be the changing longwave pattern overhead leading to gusty onshore winds. An upper level shortwave trough currently upstream will sweep through the state this afternoon. As such onshore flow will ramp up through the day and peak close to 5 mb for SFO-SAC. That translates to gusty winds 25-40 mph for the coast, mts, gaps/passes. Could even see some isolate gusts up to 50 mph for the East Bay Hills. The passing trough will also usher in some drier air leading to fire weather concerns. See Fire Section below for details. If one happens to look at satellite you`ll notice the Madre Fire currently burning in SLO. Given transport flow smoke from this fire is currently not expected to impact the forecast area. && .LONG TERM... Issued at 315 AM PDT Thu Jul 3 2025 (Friday through Wednesday) By Friday, the shortwave trough will have exited to the east as broad troughing will remain over the West. Therefore, a cloudy start to the 4th of July is expected with some afternoon sunshine. Temperatures will be mild, but seasonably cool for early July. What about clouds impacting evening activities? Definitely possible as the marine layer begin to move inland. Greatest impacts will be for the immediate coast, Monterey Bay region, and through the Golden Gate. For the upcoming holiday weekend - seasonably cool with night/morning clouds and inland afternoon sunshine. Early next becomes a little more uncertain as guidance develops another cut- off low off the Bay Area coast. Upper lows are always tricky with regards to marine layer development and possible precip. This low looks to be dry, but we`ll keep an eye on it. By Wednesday this feature drifts north as a Four Corner high builds westward. The building ridge will kick off a warm trend. && .AVIATION... (18Z TAFS) Issued at 1012 AM PDT Thu Jul 3 2025 IFR to MVFR conditions currently at the Monterey Bay terminals and coastal spots such as HAF. Low ceilings are forecast to gradually scatter out and lift through the morning and early afternoon. However, coastal locations such as MRY and HAF have a greater probability of IFR/MVFR ceilings to persist throughout much of the day. Onshore winds increase this afternoon, stronger than previous days! Vicinity of SFO...VFR. High confidence for a windy day with gusts expected to reach or exceed 35 kt at the terminal. Winds ease slightly after sunset yet remain out of the west to northwest into Friday. Low confidence for MVFR ceilings to return early Friday morning, OAK would be mostly likely if any do develop. Any low clouds that do develop will scatter out and/or lift by around 16Z Friday with increasing onshore winds. SFO Bridge Approach...Moderate to high confidence for VFR conditions over the approach through the forecast period. Monterey Bay Terminals...Currently IFR to MVFR forecast to lift to MVFR to VFR by late morning or early afternoon. West to northwest winds increase this afternoon with gusts up to 25 kt at SNS, before easing after sunset. High confidence for IFR to MVFR to return late this evening and potentially lowering to LIFR early Friday morning. && .MARINE... (Today through Tuesday) Issued at 424 AM PDT Thu Jul 3 2025 Gusty northwesterly winds and rough seas will continue through late today. Gale force gusts will be likely across northern waters through today. Winds easing by early next week. A low-amplitude long period southerly swell will arrive today and persist through Friday. && .FIRE WEATHER... Issued at 315 AM PDT Thu Jul 3 2025 No real change from previous thinking. Increasing winds this afternoon and lower humidity will create near critical fire weather conditions. Areas of greatest concern continue to be the East Bay Hills, Eastern Santa Clara Hills, and Santa Cruz mountains. Winds will be gusts 25-40 mph with isolated gusts up to 55 mph (Think Altamont Pass). The current wind forecast and state of the fuels will allow for a spike in the Burn Index for the Diablo/Santa Cruz region. Predicted values will exceed the 97 percentile. Simply put, be one less spark, especially with the holiday and potential firework impacts. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay-SF Bay N of Bay Bridge. Small Craft Advisory from 3 PM to 9 PM PDT Friday for Mry Bay-SF Bay N of Bay Bridge. Gale Warning until 3 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 PM PDT Friday for Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory from 9 AM to 9 PM PDT Friday for Pigeon Pt to Pt Pinos 0-10 nm. Small Craft Advisory until 3 PM PDT this afternoon for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning from 3 PM this afternoon to 9 PM PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Gale Warning until 9 PM PDT this evening for Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory until 9 AM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM. && $$ UPDATE...Bain SHORT TERM...MM LONG TERM....MM AVIATION...RGass MARINE...RGass 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