Marine Weather and Tide Forecast for Walnut Creek, CA

UPDATE
Issued at 842 AM PDT Mon May 18 2026

Gusty offshore winds continue through this morning with winds gradually easing this afternoon/evening. The Wind Advisory remains on track to expire at 11AM PDT across the higher elevations.
Notably, the current hourly temperatures are running 6-7 degrees above what the current forecast has. This is likely due to the stronger offshore (NE) winds bringing in warmer and drier air, with some additional warming from downsloping occurring at the base of the mountains. Bumped temperatures up using the NBM90th percentile to better account for the already warmer temperatures observed this morning. This puts the interior into the 80s to low 90s today with the coast staying in the 70s. Winds don't look to switch onshore again until after peak heating (3/4PM) so would not expect much marine influence on today's high temperatures outside of the direct coastline.

SHORT TERM
Issued at 1147 PM PDT Sun May 17 2026 (Tonight through Monday)

An upper level low pressure system digs into the tri-state area of CO, UT, and WY by late Monday morning. We remain under the influence of the broader trough associated with it, leading to breezy offshore flow. North to northeast winds pick up tonight across the Santa Cruz Mountains, the interior North Bay Mountains, and the Eastern Santa Clara and East Bay Hills. Sustained wind speeds of 15 to 30 mph along with gusts up to 50 mph, though localized gusts up to 60 mph are expected for favored ridges, gaps, and passes. These winds will usher in drier air to the region as well, keeping the fire weather threat elevated for interior Bay Area and Central Coast locations.
In terms of more every day hazards from the winds, impacts include, but are not limited to difficult driving, especially for high profile vehicles, downed tree limbs, the potential for power outages, and the possibility of loose or unsecured items being blown around.

Winds begin to ease late Monday morning into the afternoon and will continue to decrease into the evening and overnight hours. Offshore winds should bring some warmer temperatures to the region, the 90s for the interior Bay Area valleys, the 60s to low 70s along the coast, and the mid 70s to low 80s for the Central Coast Valleys.

LONG TERM
Issued at 1147 PM PDT Sun May 17 2026 (Tuesday through next Sunday)

Upper level troughing looks to hold just west of the Desert Southwest and into southern CA Tuesday into Wednesday, leaving us with teetering between quasi-zonal and barely trough-y. Weak offshore lingers at least over the interior mountain ranges through Tuesday into Wednesday, with onshore flow trying to make a diurnally driven push each afternoon/evening. During this time high pressure just to the west of us (over the eastern Pacific) builds, pushing towards the coast mid week. The upper level trough begins to meander south to southwest of southern California late week. This should bring a return of onshore flow to the region and perhaps the marine layer. Current guidance suggests we could see a 500ft marine layer return by Wednesday, with a 1000-1200ft marine layer by Thursday and Friday. Will need to keep an eye on this as it will affect how temperatures pan out.

AVIATION
(18Z TAFS)
Issued at 1021 AM PDT Mon May 18 2026

VFR conditions prevail through the TAF period. Breezy and gusty northeast winds will gradually diminish through the next couple of hours as an onshore push returns to the coastal regions this afternoon, with the coastal breeze continuing through the evening.
Breezy winds will continue across the interior mountains of the Bay Area through the night, with northeast winds spreading across the interior valleys Tuesday morning towards the end of the 24-hour TAF period. Beyond that, Tuesday's coastal breezes look to be stronger than today's.

Vicinity of SFO... VFR conditions through the TAF period. Breezy and gusty northeast winds will turn more northwesterly through the afternoon, before diminishing through the evening and remaining light overnight through Tuesday morning. West-northwest winds will resume on Tuesday afternoon.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... VFR conditions through the TAF period.
Breezy northwest winds will develop imminently and continue into the evening. Winds remain light overnight before resuming Tuesday afternoon after the end of the TAF period.

MARINE
(Today through Saturday)
Issued at 1021 AM PDT Mon May 18 2026

Winds continue to diminish throughout the marine environment, but moderate to rough seas and moderate to fresh northwest breezes will still offer hazardous conditions for small craft into the mid weak before easing for most zones. Fresh to strong northwest breezes will remain hazardous for small craft into the late week for the northern outer zone.

FIRE WEATHER
Issued at 449 AM PDT Mon May 18 2026

Strong and gusty north to northeast winds continue to affect the region. 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. These winds will begin to reduce in the late morning but remain breezy until the late night. Daytime humidity retentions loos to stay around 10- 25% across the interior regions and higher peaks, with limited overnight humidity recoveries.
Humidities will be slow to recover into the work week as a light offshore flow will continue to affect the district.

MTR WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory until 11 AM PDT this morning for CAZ504-512-514- 515.

Coastal Flood Advisory until 3 AM PDT Tuesday for CAZ506.

PZ...Small Craft Advisory until 3 PM PDT this afternoon for SF Bay N of Bay Bridge.

Small Craft Advisory until 9 PM PDT this evening for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory until 3 AM PDT Tuesday for Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory until 3 AM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory until 9 AM PDT Tuesday for Pigeon Pt to Pt Pinos 10-60 NM.