Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

411 pm PDT Mon Sep 28 2026

Short Term

, Issued at 1205 PM PDT Mon Sep 28 2026 (This evening through Tuesday night)

The stratus has largely cleared out with some isolated patches continuing at the immediate coast. Probability of stratus development tonight is low to very low, as incoming ridging and offshore flow will generally disrupt the marine layer stratus formation processes.

The latest water vapor imagery shows an upper level low tracking across the southern Central Valley into the Mojave Desert, expected to continue trekking southeastward through the day and entering Arizona by Tuesday morning. Behind the low, an incoming ridge kickstarts a warming trend that will extend through the next couple of days. Today's high temperatures range from the middle 70s to middle 80s inland to the upper 60s to middle 70s along the Bays and the lower to middle 60s at the Pacific coast. On Tuesday, high temperatures will reach the middle 80s to middle 90s inland, the middle 70s to middle 80s along the Bays, and the middle 60s to lower 70s at the Pacific coast.

With the northerly flow aloft as the upper level low moves towards the southeast, a push of offshore wind is expected in the higher elevations Tuesday morning. Gusts of 25 to 35 mph are expected along the exposed ridgelines, and stronger gusts are possible along the ridge of the Vaca Mountains along the Napa-Yolo and Napa-Solano county lines. Elsewhere, generally diurnal winds will prevail with onshore winds developing each afternoon and evening, with gusts to 30 mph along the coast, through favored gaps and passes, and within the Salinas Valley.

Minor coastal flooding is possible across the bayshore locations of San Francisco Bay, San Pablo Bay, and Monterey Bay around high tide starting today. Up to 1.2 feet of inundation above normally dry land is expected, including up to 0.6 ft of surge caused by thermal expansion and sea level rise since the sea level datum (basically the point where we define as "sea level") was set in the 1983-2001 period. At the San Francisco tidal gauge, high tide is expected to be 1.0 ft above normal (6.87 ft MLLW) at 12:57 PM Monday 9/28 and 1.2 ft above normal (7.01 ft MHHW) at 1:30 PM Tuesday 9/29.

Long Term

..issued at 1205 PM PDT Mon Sep 28 2026 (Wednesday through next Sunday)

There is an additional push of higher elevation offshore flow on Wednesday morning. This push will be more focused on the interior mountains of the North and East Bay with gusts a little lighter than those expected on Tuesday morning. Otherwise, temperatures may fluctuate by a few degrees each day, most notably on Thursday when stronger onshore flow will cause some of the coastal regions to dip by a few degrees, but the general trend should remain similar to Tuesday's highs through the end of the seven day outlook. Areas of Moderate HeatRisk, a level of heat that brings a moderate risk of heat-related illnesses to sensitive populations, develop across the interior regions Wednesday through Saturday, but confidence in widespread impacts is not high enough to issue a Heat Advisory at this point. Longer-range guidance suggests that temperatures above the seasonal average will continue into the second week of October.

Minor coastal flooding around high tide continues in low-lying areas across the San Francisco, San Pablo, and Monterey Bay shorelines through Thursday and potentially into Friday. At the San Francisco tidal gauge, high tide is expected to be 1.2 ft above normal (7.03 ft MHHW) at 2:10 PM Wednesday 9/30, and 1.1 ft above normal (6.92 ft MHHW) at 2:58 PM on Thursday 10/1.

Aviation

(00z TAFS) Issued at 410 PM PDT Mon Sep 28 2026

VFR conditions prevail across most of the region through the night and into Tuesday, with some MVFR-IFR ceilings possible overnight at the immediate coast and particularly near Monterey Bay. A moderate onshore wind continues through the evening hours, diminishing overnight before gentle to moderate onshore winds resumes Tuesday afternoon.

Vicinity of SFO, VFR through the TAF period. Breezy northwest winds with strong gusts continue into the late evening hours, diminishing overnight before resuming Tuesday afternoon.

SFO Bridge Approach, Similar to SFO

Monterey Bay Terminals, Patchy stratus lingers at the immediate coast and has just come over MRY. Lower confidence in stratus development at SNS; kept the terminal VFR through the night. Stratus will mix out to the immediate coast Tuesday morning. A moderate onshore wind continues through the evening hours, with light drainage flow overnight before onshore winds resume Tuesday afternoon.

Marine

(tonight through next Saturday) Issued at 410 PM PDT Mon Sep 28 2026

A strengthening pressure gradient along the California Coast will keep moderate to strong northerly breezes through Wednesday. Strongest winds will be the outer waters north of Point Reyes and along the Big Sur Coast. Rough seas will accompany the winds and will subside to moderate by the end of the week. Tropical activity will produce long period swell up to 16 seconds Wednesday and Thursday.

Watches, Warnings, Advisories

Ca, Coastal Flood Advisory until 5 PM PDT Thursday for CAZ006-506- 508-529-530.

PZ, Small Craft Advisory until 3 AM PDT Wednesday for Pt Arena to Pt Reyes 0-10 nm.

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

Small Craft Advisory until 11 PM PDT this evening for Pt Pinos to Pt Piedras Blancas 0-10 nm.

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

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