Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

239 pm PDT Sun apr 19 2026

Short Term

, Issued at 235 PM PDT Sun Apr 19 2026 (This evening through Monday)

Pleasant end to the weekend for the Bay Area and Central Coast weather wise with filtered sunshine and seasonably mild temperatures. Max temps today will peak in the 60s to mid 70s with a few interior spots making a run at 80 plus.

Stepping back and taking look at the bigger picture reveals a system lurking off the coast. In fact, pretty impressive looking visible satellite imagery this afternoon. A discernible circulation is spinning off the PacNW with a band of clouds wrapping around the system and stretching along the West Coast. The circulation is an anomalously deep upper low. At the surface is a double barrel low pressure system with a marked frontal structure. The surface low and front will begin to inch its way eastward Sunday evening and Sunday night. The advancing cold front will bring increasing clouds and a few scout showers to the northern coastal waters and far northern Sonoma county. Not expecting much in the way of accumulating precip with these leading showers through Sunday night.

More widespread precip is expected on Monday as the highly amplified upper jet begins to phase off the CA coast. Light to moderate rain will begin across the North Bay toward the end of the AM commute. Rain will spread S and E through the day with the passage of the cold front. Expect the evening commute to be pretty messy with wet roads.

In addition to the rain on Monday, southerly flow will ramp thanks to a tightening surface gradient. Winds are initially strongest over the waters before hitting the coast and inland areas by the afternoon. Not strong enough for a wind advisory, but general gusts in the 30-40 mph range seems reasonable. Given the southerly flow, initial rain chances for some areas will be eaten thanks to downslope flow and rain shadowing.

As for temperatures, despite a pattern change temperatures will be mild since the region will be in a warmer sector until fropa. Given the solid S flow think there could be some enhanced downslope warming - thinking Monterey.

Long Term

..issued at 238 PM PDT Sun Apr 19 2026 (Monday night through next Saturday)

Monday looks wet, but Tuesday may end up being a little more dynamic thanks to convection. A few things we'll be watching for Tuesday: cold pool aloft behind the front destabilizing the atmosphere, approaching upper low, position of left exit of jet aloft, and wind profiles relating to low level shear. While those pieces varying from model to model, enough of a signal is present to justify having thunderstorms in the forecast for Tuesday. Putting things into better context, the ECMWF Extreme Forecast Index has strong signal for CAPE over the coastal waters giving more confidence to thunderstorms. SPC Day 3 outlook does have the entire region in a general mention of thunderstorms.

Monday's rain and Tuesday additional shower activity should be mostly beneficial rain, but given the convective nature local ponding/minor flooding is possible. Lingering showers will continue into Wednesday afternoon thanks to a trailing shortwave behind the departing upper level low/trough.

Warmer and drier conditions there after.

Aviation

(18z TAFS) Issued at 1152 AM PDT Sun Apr 19 2026

High clouds are building across the area with moderate winds building into the afternoon. Winds become light into the evening and into the night with mostly variable to southerly winds expected. The next cold front begins to enter the region from the northwest into the late night and early morning. Southerly winds build ahead of the front with light prefrontal showers. Rain and winds increase along the front with gusty southerly winds expected. Rain and winds continue well beyond the TAF period, with increased rain rate predicted further into Monday.

Vicinity of SFO, VFR through the TAF period. High clouds will build through the day with moderate west to southwest winds. Winds weaken and turn slightly more southerly into the night. Light showers arrive along with moderate southerly winds into Monday morning. Gusty south winds build into the late morning on Monday as rain rates begin to increase.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, VFR through the TAF period. High clouds continue to build into the areas with moderate to breezy winds expected this afternoon and through the evening. Winds reduce into the night and become light. Southeast winds begin to build at SNS into mid Monday morning. Showers and increased winds arrived beyond the TAF period.

Marine

(today through Friday) Issued at 1152 AM PDT Sun Apr 19 2026

Expect breezy and gusty winds to build ahead of a slow moving cold front that arrives on Monday. Rain will accompany the cold front starting Monday and lingering into early Wednesday. Chances of thunderstorms will move through the waters for much of Tuesday. Dry weather returns late in the week.

Watches, Warnings, Advisories

Ca, None. PZ, Small Craft Advisory from 9 AM to 9 PM PDT Monday for SF Bay N of Bay Bridge.

Small Craft Advisory from 9 AM Monday to 3 AM PDT Tuesday for Mry Bay.

Small Craft Advisory from 3 AM to 9 PM PDT Monday 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-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory from 3 AM Monday to 3 AM PDT Tuesday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm.

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