Marine Weather and Tide Forecast for Walnut Creek, CA

UPDATE
Issued at 955 AM PDT Sun May 17 2026

Winds are expected to increase again this afternoon/evening. A Wind Advisory will go into effect at 11 PM PDT tonight and continue through 11 AM PDT Monday for the higher elevations of the North Bay, East Bay, South Bay, and Santa Cruz Mountains. Gusts up to 50 mph are expected across the higher elevations with localized gusts up to 60 mph possible along the highest ridgelines.
Otherwise the forecast remains on track.

SHORT TERM
Issued at 140 AM PDT Sun May 17 2026 (Today and tonight)

Water vapor imagery shows a broad trough of low pressure over the West this morning, with one disturbance currently moving across Nevada. In response to this system beginning to shift east, pressure gradients are starting to relax from their earlier peak.
At this time, the SFO-ACV is down to -9.5 mbs, while the SFO- LAS is down to 12.6 mbs. Even though it is still breezy out there, gusts are mostly less than 40 mph along the coast. Therefore, have canceled the Wind Advisory to better reflect the current conditions.

That being said, the winds will still be a concern over the next 24 to 36 hours though, as another disturbance currently over Western Washington and Oregon dives into the Great Basin later today and tonight. This disturbances has a more traditional inside slider trajectory. As a result, expect another round of dry and gusty winds to develop. This time though, it will be the offshore pressure gradients that increase. North to northeast 925 mb and the 850 mb winds will increase to 40 kts over the North and East Bay after 06z Mon, before spreading south and west through the night. Therefore, have issued a new Wind Advisory focusing on the North, East, and South Bay Mountains as well as the Santa Cruz Mountains for Sunday night through late Monday morning. At this point in time, expect the gusts to be in the 45 to 55 mph range, with local gusts above 60 mph at the favored locations like Mount Diablo. Very dry conditions will accompany these winds, and should a fire start in dry grass areas, the fuels will carry that fire.
Therefore, caution is encouraged if you have plans to be working outdoors. One less spark.

LONG TERM
Issued at 140 AM PDT Sun May 17 2026 (Monday through Saturday)

As this the broad trough starts to push east on Monday, high pressure will start to rebuild over California, and be the dominate weather feature through midweek. As a result, a gradual warming trend will develop, especially across the inland areas. Expect some warming at the coast as well, but it will be more moderated, especially once the marine layer re-estabilishes itself by Wednesday. Models start to diverge towards the end of the week and next weekend, with some clusters suggesting another trough forming off the West Coast, while others suggest a flatter ridge, while others suggest the ridge persisting. Therefore, confidences is relatively low on what will actually happen. However, believe the marine layer will likely continue to bring low clouds and fog to the coastal areas. The question is just how far inland that influence will go. Palmer

AVIATION
(18Z TAFS)
Issued at 1113 AM PDT Sun May 17 2026

Strong surface high pressure over the eastern Pacific and far northern CA is resulting in a moderate to strong northerly 7.4 mb ACV-SFO pressure gradient including 2.0 mb SFO-SAC onshore pressure gradient. RDD-SAC is 4.1 mb while the surface pressure will also build over the Great Basin increasing the WMC-SFO gradient tonight and Monday morning as well. Mixing and drying within the boundary layer will result in continuing VFR. Windswept seas leading to sea spray and sea salt aerosols will continue to result in areas of reduced visibility in haze /MVFR/ near the coastline. Surface winds at the terminals ease tonight while lower level winds will increase resulting in areas of low level wind shear tonight and Monday morning. Lower level winds decrease while diurnal vertical mixing returns Monday reducing low level wind shear during the day Monday.

Vicinity of SFO...VFR. West wind increasing to 20 to 30 knots in the afternoon to mid evening. Wind decreasing tonight to 10 knots with low level wind shear tonight and Monday morning. Northwest wind strengthens by late Monday morning with a decrease in low level wind shear.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR except for areas of haze /MVFR/. West winds 15 to 25 knots, easing to 5 to 10 knots tonight and Monday morning. Low level wind shear tonight and Monday morning.

MARINE
(Today through Friday)
Issued at 955 AM PDT Sun May 17 2026

Strong surface high pressure will remain nearly stationary over the eastern Pacific this week. This will result in widespread strong and gusty northwest winds across the coastal waters. Rough seas continue through late today with up to 19 ft waves during the strongest winds, but seas will ease into the work week.

FIRE WEATHER
Issued at 443 AM PDT Sun May 17 2026

Strong and gusty north to northwest winds continue to affect the region, shifting slightly into Sunday afternoon, and becoming north to northeast. Expect peak gusts greater than 30 mph for most areas, with around 45 to 55 mph along through gaps and passes, and across higher terrain. Daytime humidity retentions loos to stay around 10- 25% across the interior regions and higher peaks, with limited overnight humidity recoveries. Strong winds persist into the early Monday before diminishing. Humidities will be slow to recover into the work week as a light offshore flow will continue to affect the district.

BEACHES
Issued at 140 AM PDT Sat May 16 2026

A Beach Hazards Statement remains in effect for west facing beaches along the Pacific Coast through 9 AM Monday due to strong winds over the marine environment leading to hazardously strong wind waves and overall rough seas. Dangerous swimming, boating, and surfing conditions can be expected. Large breaking waves can overpower swimmers resulting in significant physical injury and increase the risk of drowning. Gusts will stay strong along the immediate coast, causing blowing and drifting sand and increased sea spray. Water rescue attempts may be hampered by reduced visibilities from the sea spray. Remember, NEVER turn your back on the ocean.

MTR WATCHES/WARNINGS/ADVISORIES
CA...Beach Hazards Statement through Monday morning for CAZ006-505- 509-530.

Wind Advisory from 11 PM this evening to 11 AM PDT Monday for CAZ504-512-514-515.

Coastal Flood Advisory until 3 AM PDT Tuesday for CAZ506.

PZ...Gale Warning until 3 AM PDT Monday for Pigeon Pt to Pt Pinos 0- 10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0- 10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm-SF Bay N of Bay Bridge.

Gale Warning until 9 PM PDT this evening for Mry Bay.

Storm Warning until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM.

Gale Warning from 3 PM this afternoon to 9 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM.