Marine Weather and Tide Forecast for Walnut Creek, CA

SHORT TERM
(Today and tonight)
Issued at 1224 AM PDT Wed Apr 23 2025

A shortwave trough is building over the West Coast, resulting in cooler temperatures and a deeper marine layer in the region.
Satellite imagery shows stratus developing along the coast from Point Reyes southward, moving inland into the Bayshore East Bay, across the Monterey Bay region, and down through the Salinas Valley and across the Gilroy-Hollister region. The enhanced marine layer will enable the stratus to develop further inland through the night, before the inland stratus gradually dissipates through the morning, while some coastal regions remain socked in through the day. Breezy onshore flow will develop this afternoon, with gusts reaching 20-25 mph through the gaps and passes. High temperatures today will top out in the upper 60s to the lower 70s in the inland valleys, and the middle 50s to lower 60s along the Bays and Pacific coast.

LONG TERM
(Thursday through Tuesday)
Issued at 1224 AM PDT Wed Apr 23 2025

Thursday is shaping up to be pretty similar to today, with an uptick in wind gusts (reaching 25-30 mph through the gaps and passes) and a downtick in inland high temperatures (middle to upper 60s).

Friday and Saturday should see the arrival of a deepening upper level trough coming through the eastern Pacific. Confidence has continued to increase in the stronger model solutions and a potential cutoff low coming into California. Combined with a southward trend in the forecast track, the trend has resulted in an increase in PoPs throughout the region, especially south of the Golden Gate. The current forecast has PoPs rising as high as 40-50% Friday night and Saturday morning. Rainfall totals remain low; although the exact spatial extent of the rainfall is quite uncertain, we're not expecting totals above a tenth of an inch in the valleys and a quarter of an inch in the higher elevations.
Something else to keep an eye on: we're starting to see some indications of thunderstorm potential on Friday evening into Saturday morning, with NBM model output putting odds of thunderstorm activity as high as 10-15%. We'll monitor how the thunderstorm risk evolves over the next couple of days. As for high temperatures on Friday and Saturday, expect anywhere from the middle 50s to the middle 60s in the lower elevations, and the middle 40s to the lower 50s in the higher elevations.

Ridging should return after the trough moves out, with daytime highs rebounding to near the seasonal average in the early part of next week.

AVIATION
(06Z TAFS)
Issued at 931 PM PDT Tue Apr 22 2025

Forecast in good shape going into tonight with MVFR/IFR cigs building in nicely along the SF Peninsula and Monterey Bay areas.
High confidence in cigs filling in around the SF Bay later tonight through sunrise Wednesday. Expecting cigs to lift a bit by the late morning hours as a trough expands the marine layer, and may end up toeing the line between MVFR/VFR before mixing out to CLR skies by the afternoon. Early return for stratus Wednesday night.

Vicinity of SFO...Breezy onshore winds through the night tonight with marine stratus filling in by the early morning hours.
Relatively high confidence forecast for the hours after sunrise, then confidence becomes a bit lower as an upper trough moves through and lifts cigs a bit by late morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals.. MVFR/IFR cigs through the nighttime hours. Hi res guidance depicts the formation of an "Otter Eddy" in the Monterey Bay, which may bring about brief periods of LIFR cigs and reduced vis for coastal areas along the southern Monterey Bay around sunrise.

MARINE
(Tonight through next Monday)
Issued at 908 PM PDT Tue Apr 22 2025

Strong, near gale winds will continue across the northern outer waters through Wednesday as a weak upper level trough passes through the region. Otherwise a fresh to strong breeze across the rest of the waters through the middle of the week. Light rain chances increase by Friday over the northern waters.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory until 9 AM PDT this morning for Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory from 9 AM this morning to 3 AM PDT Thursday for Pt Pinos to Pt Piedras Blancas 0-10 nm.