textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1151 PM PDT Wed May 27 2026

- Cool, unsettled weather continues today

- Slight chance of isolated strong thunderstorms from mid-morning through mid-afternoon for southern South Bay and Central Coast

- Warming and drying trend Friday and beyond

SHORT TERM

Issued at 1151 PM PDT Wed May 27 2026 (Tonight through Friday)

A steady fetch of light rain, on the backside of the retrograding upper level low responsible for the unsettled weather the past couple of days, will continue over the North Bay and Bay Area much of the overnight into early Thursday morning. A large portion of Sonoma and Marin County (especially higher elevations) have a 50%- 60% chance of exceeding 0.25" rainfall or more by sunrise.

Relatively weak cyclogenesis will generate a surface low, just offshore of Marin County and San Francisco County, late in the overnight hours. As the upper level disturbance begins its shift into the interior, the accompanying surface low will hug the coastline for the remainder of the day. After sunrise the coastal ranges of Santa Cruz south through the Santa Lucias along the Big Sur coast will receive the most rainfall with efficient orographic lift. Santa Cruz mountains have ~20% chance of exceeding 1.00" of rain during the day, and ~75% chance of exceeding 0.50" of rain. From the Monterey Peninsula south through the Big Sure, looking at ~80% or higher chance of 0.50". The highest spots of the Santa Lucias along the Big Sur have ~50% chance of 1.00" or more. Flooding concerns are minimal given mean rainfall rates of 0.10"-0.20"/hr.

As the upper low begins a more eastward shift inland from mid morning into the afternoon, chances for thunderstorms over the interior begin to increase. Coverage of showers and isolated thunderstorms have over performed somewhat, especially yesterday. HiRes CAMs have steadily shown 100-200 (some spots slightly higher) J/Kg of CAPE from the South Bay and the remainder of the interior Central Coast from late morning into mid-afternoon today. That has been enough to sustain convective showers (with periods of moderate rainfall) with isolated thunderstorms Tuesday and Wednesday. A limiting factor the past couple of days has been a lack of wind shear and only pockets of weak divergence aloft. That will change this morning and continue through the afternoon with ~25-30kts of 0-6km at any given time (sometimes more) from 8am PDT through mid-afternoon and a larger swath of divergence aloft near the base of the exiting closed low aloft. Along with potential terrain influences, there will be surface convergence into the surface low riding the coastline and some slightly backed H85 flow at times. Overall, this is to say a brief low-top supercell can't be ruled out from Santa Cruz County-southern Santa Clara county around mid- morning and farther south into the Central Coast for the remainder of the morning into the afternoon hours. By late afternoon the potential for strong storms drops off quickly with only lingering light rain expected in the North Bay and southern Monterey County through the evening hours.

LONG TERM

Issued at 1151 PM PDT Wed May 27 2026 (Friday night through next Wednesday)

Not much change in the extended forecast with some uncertainty in the finer details of the overall synoptic pattern, but we do know that we will begin to dry out and temperatures will begin to warm closer to seasonal averages through the weekend and slightly above normal for the the first half of next week at least. The pattern is relatively progressive and does not indicate any impactful extreme heat in our area through the extended forecast.

AVIATION

(12Z TAFS) Issued at 427 AM PDT Thu May 28 2026

Generally MVFR or low end VFR throughout the region, with patches of IFR along the coast, as steady rain blankets the North Bay and comes into the Bay Area. Through the rest of the day, the offshore low pressure system associated with the rainfall will travel southwards parallel to the coast, bringing the rain into the rest of the Bay Area and the Central Coast. Lower visibilities are possible if a shower comes over a terminal. A slight chance (10-20% probability) of thunderstorms is possible later this morning into the afternoon across the Central Coast, but the probabilities are too low to include in the TAFs at this time. On the backside of the rain, expected to arrive late morning across the North bay into the late evening across the Central Coast, MVFR to low-end VFR ceilings will linger into the night. Confidence in the wind directions is low to moderate, and may depend on the exact location and position of the low, especially closer to the coast. The general trend is for some breezy onshore flow to develop this weekend into the evening, with the wind pattern on Friday afternoon beyond the TAF period expected to align with northwest flow. Some high resolution models are showing breezy southeast winds developing across the region this morning, but this is a lower confidence forecast. Will monitor the observed conditions through the morning.

Vicinity of SFO... Steady rain expected to continue through the morning with MVFR to low-end VFR ceilings expected through the TAF period. Light southerly winds will turn to a breezy west flow this afternoon and evening, diminishing through the night before returning Friday afternoon beyond the end of the TAF period.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Steady rain expected imminently across the terminals through the day, with the rainfall expected to turn more showery in the afternoon. The highest probability for thunderstorms lies to the south of the terminals, with around a 10% probability of thunderstorms at the terminals themselves, but can not rule out a stray cell moving over MRY or SNS through the later morning and afternoon hours. Strong valley winds are possible at SNS this morning, with some high resolution models suggesting gusts as high as 20-25 knots. Elsewhere, breezy winds develop later this morning and last until evening, before easing overnight.

MARINE

(Today through Tuesday) Issued at 427 AM PDT Thu May 28 2026

Winds continue to diminish across the coastal waters through the morning, as light to gentle winds revolve around a low pressure system paralleling the coast across the coastal waters through the day. Moderate to fresh northwest winds develop Friday, then strong to near gale force northerly winds return over the weekend and continue into next week. Rough seas persist across the outer waters while seas abate to moderate in the inner waters. Wave heights build as winds restrengthen with wave heights between 10 to 12 feet expected this weekend into early next week.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement from 9 AM PDT this morning through late tonight for CAZ006-505-509-529-530.

PZ...Small Craft Advisory from 3 PM Friday to 9 AM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory from 9 PM Friday to 9 AM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.

Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM.