, Issued at 1215 AM PDT Sun May 10 2026 (Today through Monday)
Let's step back and take a look at the interesting longwave pattern over the CONUS - ridge of high pressure covers CA which is bookended by deep troughs on either side with one near the Great Lakes and the other near Gulf of AK. The pattern will hold in the near term, but will shift with a pattern change on the horizon, literally. So what does this set up mean for the Bay Area? A ridge of high pressure in May usually brings dry and mild conditions and Sunday is no exception. However, it's the details that matter. Overnight satellite imagery shows solid stratus along the coast working its way inland. The marine layer will likely top out 900-1200 feet this morning and will be the spoiler for Max T potential. Would not be surprised one bit if the marine layer was able to squeeze out some drizzle along the coast. Model guidance has struggled the last few days regarding Max T and the marine layer influence, simply put the forecast was too warm. As such, trended temperatures downward from the NBM over inland valleys or areas that have a pronounced marine layer influence this afternoon. Went colder by 3-5 degs, but worried it wasn't under cut enough. That being said, do expect the marine layer clouds to erode back to the coast by this afternoon with inland sunshine and coastal clouds. Regardless, if you have outdoor activities to celebrate Mother's Day it will be pleasant with inland highs in the 70s and 80s and cooler at the coast in the 60s - bring a jacket. Could also be a tad breezy this afternoon with the temp difference from the coast to interior. Sfc pressure gradients remain onshore again, but are forecast to be weaker than Saturday where they peaked at 4.2 mb.
Sunday night through Monday - the center of the upper ridge begins to shift toward the Desert SW while the upstream trough deepens and inches toward the West Coast. Despite the shift, Monday is still on track to be the warmest day of the forecast. 850 mb temps peak at 20-22C. Mixing those temps to the surface under ideal conditions would bring toasty temps. However, we still have some onshore flow and lingering marine layer. As such, max temps will be tempered near the coast and bays, 60s to lower 80s. Far interior locations will be in the 90s leading to some Moderate HeatRisk.
..issued at 1220 AM PDT Sun May 10 2026 (Monday night through next Saturday)
The change in the longwave pattern begins to unfold Monday night into Tuesday. The upper level ridge is being replaced by a robust and anomalously deep upper low for mid May. Temperatures begin to drop in response to lower 500 mb heights and cooler 850 mb temps, but still above normal.
By Wednesday near normal temperatures return thanks to the cut-off low over the region. Confidence fades on the details of the exact placement of the cut-off low, cluster analysis is split with some favoring more zonal flow and others farther south with a deeper low. Regardless of exact placement, it's clear that temps drop and at least some drizzle is likely. A few members even show light showers Wednesday afternoon/evening (tstorms to the N).
Zonal flow returns for the second half of the work week leading to rebounding temperatures and drier conditions.
(12z TAFS) Issued at 509 AM PDT Sun May 10 2026
Nearly ideal conditions exist for marine stratus /MVFR-IFR/ with satellite showing fairly widespread coverage across the Bay Area and north Central Coast. Despite that there's a strong 500 mb ridge and warmth aloft (00z Saturday evening Oakland upper air sounding mandatory levels aloft were near 90th percentile for mid May), the marine layer is well defined with an inland intrusion supported by a 2.8 SFO-SAC pressure gradient. Travis AFB has had onshore gusts to 30 knots overnight for example. The marine layer varies in depth from 1200 feet to 2000 feet. 24 hour trends show steady to slightly higher surface dew point temperatures i.e. steady to greater amount of water vapor trapped beneath the marine temperature inversion. In the dry air above the marine layer temperature inversion, nocturnal radiative cooling like previous early mornings is good; forecast soundings show a similar vertical distribution of low water vapor/dry aloft tonight and Monday morning supportive of cooling again tonight and Monday morning.
Run after run of the HRRR overnight continues to show stratus clouds beginning to mix out prior to sunrise, which is highly unlikely to happen this early. The NAM shows stratus lingering until late morning which seems more reasonable. The ACV-SFO pressure gradient is currently 3.7 mb and is forecast to increase later today to the evening before decreasing overnight, but there's disagreement as to the strength of this gradient for today. Overall, it's a challenging forecast not only for the public side and temperatures, but also for aviation side and ceilings forecasts. There's been a steady application of northwest winds over the coastal waters, producing some cold water upwelling with sea surface temps near to 3F or 4F above May normals.
It'll take the higher Sun angle of May to break through the stratus layer via vertical mixing today. Clearing times are mainly by late morning, though it may take an hour or two longer than that depending how well the stratus holds together through morning. For tonight and Monday morning, expect stratus including patchy fog to develop with MVFR-IFR-LIFR late tonight and Monday morning.
Vicinity of SFO, Stratus /IFR/ intrusion is well established this morning per satellite and surface observations. Near 100% IFR probability on HREF at least early this morning, may also correspond to patchy light drizzle (from KHAF to KSFO to KOAK). For the time being, 12z SFO TAF is for dry runways. Stratus IFR ceiling increasing to MVFR by late morning with mix out by 20z today. Stratus /IFR/ returns 07z tonight with stratus prevailing through much of Monday morning. West wind 10 knots with a few gusts to 20 knots still possible this morning, otherwise increasing west wind 15 to 25 knots from late morning through the afternoon to early evening. West wind near 10 knots tonight and Monday morning.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Stratus /IFR/ covers the Monterey Peninsula with stratus extending far into the Salinas Valley; the marine layer is ~ 2000 feet deep here in this part of the forecast area. A few patches of light drizzle are possible during the morning. Stratus /IFR/ conditions gradually improving to MVFR by late morning or early afternoon. Stratus /IFR/ returns tonight and Monday morning. West to northwest winds 5 to 15 knots.
(today through Friday) Issued at 403 AM PDT Sun May 10 2026
Moderate seas and fresh to strong northwest breezes with occasional near gale force gusts will continue through most of today. Locally gusty conditions are likely across the San Pablo and San Francisco Bays where terrain promotes wind funneling. Winds gradually ease starting late today with a gentle to moderate northwesterly breeze expected early to mid week. Breezy conditions return to the inner waters late week and seas build mid to late week.
Ca, None. PZ, Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay.
Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory until 9 PM PDT this evening for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm- Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory until 3 PM PDT Monday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
