Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

849 pm PDT Fri jul 31 2026

Update

Issued at 849 PM PDT Fri Jul 31 2026

It was another hot day cross the interior. In fact, far interior locations over performed with the hottest locations ranging from 100-107 degrees. The 107 was at Pinnacles NP. Closer to the coast and bays were warmer than Thursday, but still the marine layer influence/onshore flow kept the real heat away. We've talked about the temperature difference at the coast and inland the past few days. We've also highlighted how sharp the temperature gradient can been in just a matter of a few miles, thinking Monterey coast to interior Monterey/Santa Lucia Range. Today let's highlight temperatures in the vertical. Once again we'll head back to Monterey county, more specifically the Big Sur coast. The marine layer has been rather shallow the last few days, but still ushering in that natural AC. Hwy 1 along the Big Sur coast had temps topped out in the 60s and 70s for the most part. Big Sur RAWS did hit 89, but that location is a little more protected. Now if you head up the hill from Hwy 1, just 700-1000 feet temps reached the low 90s. Anyone who hikes or trail runs in the Santa Lucia range in July knows this happens a lot. Regardless, pretty impressive.

No evening update is expected. For those looking out the window who live near the coast may see something they didn't last night, clouds. The persistent NW flow and upwelling is more supportive of stratus tonight. Latest satellite imagery shows way more clouds than last evening. Expect the coverage of clouds to fill in along the coast. Two areas where clouds may not form due to weak offshore flow will be the Sonoma and Big Sur coasts.

Short Term

, Issued at 1251 PM PDT Fri Jul 31 2026 (This evening through Saturday night)

Patches of stratus persist across the coast of the San Mateo Peninsula and the Monterey Bay region, where an eddy over the bay is keeping the stratus in place for a little while longer. Across the region, skies are generally clear with smoke impacts from the Woodside Fire observed across the Sonoma County valleys, and to a lesser extent across the North Bay. A gradual warming trend continues today as the high pressure system over the Desert Southwest continues to impact our weather pattern. Highs today range from the 90s in the inland valleys, up to 104 in the warmest spots of southern Monterey and San Benito counties, to the middle 70s to lower 80s near the Bays, and the middle 60s along the Pacific coast. Gusty onshore winds will develop this afternoon and evening, with gusts reaching 25 to 35 mph along the coast, through gaps and passes, within the Salinas Valley, and at the ridgelines. High temperatures will be a couple degrees warmer on Saturday, with triple digit highs possible in isolated locations in the far interior North and East Bays, with winds ramping up in the coastal waters as a passing trough tightens the pressure gradient. With the stronger winds now coming into the domain of more of the higher resolution modeling suites, the forecast is calling for more widespread gale force gusts with isolated storm force gusts possible in the northern outer waters.

Regarding the Woodside Fire, northwest winds will continue to impact the wildfire site through the day with gusts of 25 to 30 mph expected this afternoon and evening. Along the immediate coast, temperatures will cool to the middle 50s with fair overnight humidity recoveries. Poorer conditions are possible in the higher elevations, where the thermal belts will result in poor humidity recoveries and low temperatures in the middle 60s to lower 70s. In terms of smoke impacts, high resolution HRRR model output depicts smoke transport generally driven by northwest winds parallel to the Sonoma County coast before the local wind pattern brings the smoke through the Petaluma Gap into the North Bay valleys. For air quality information, refer to products issued by the Northern Sonoma County Air Pollution Control District within northern and western Sonoma County, and the Bay Area Air Quality Management District in the rest of the North Bay and SF Bay Area.

Patches of Moderate HeatRisk are expected to develop across the interior today, followed by more widespread Moderate HeatRisk in the interior Saturday through the early part of next week. This corresponds to a moderate risk for heat related illnesses for sensitive populations, including children, the elderly, pregnant women, people with certain medical conditions, and people who work or live outdoors without adequate shelter or hydration. Considered issuing a Heat Advisory for the weekend, but at this point there hasn't been enough forecast coverage of the Moderate HeatRisk to pull the trigger on issuing the Heat Advisory as of yet. Follow these tips to avoid heat-related illnesses:

* Stay hydrated and drink plenty of fluids. * Wear lightweight, light-colored clothing. * Reduce time spent outdoors or stay in the shade. * Never leave people or pets unattended in vehicles. * Use sunscreen if going to the coast or the pool.

As a final note, beach hazards and fire weather concerns continue into the weekend. See the BEACHES and FIRE WEATHER sections for more details. One less spark, one less fire, and never turn your back to the ocean!

Long Term

..issued at 1251 PM PDT Fri Jul 31 2026 (Sunday through next Thursday)

The heat continues into Sunday and Monday as the trough passes by far to the north across western and central Canada, leaving the ridging pattern generally intact through the early part of next week. The current forecast shows a gradual cooling trend beginning on Tuesday, but model ensemble cluster analysis generally agrees on some form of ridging staying in place through the next week, with the end result that temperatures are slow to drop and could remain slightly above the seasonal average through the first week of August.

The upper level pattern could bring us a couple of offshore bursts over the region, with a notable pulse Sunday night into Monday particularly across the North Bay and SF Bay regions. Fire weather concerns regarding nocturnal drying and downslope warming are obvious, but that downslope warming could also cause coastal temperatures to be much warmer than the forecast if it extends through Monday.

Aviation

(00z TAFS) Issued at 431 PM PDT Fri Jul 31 2026

VFR conditions are expected to continue until after midnight with the exception of KMRY and KHAF. Low confidence on MVFR/IFR ceilings and timing for non-coastal sites during the overnight hours. The marine layer will continue to be compressed with weak organization indicated by the 00Z KOAK balloon.

Vicinity of SFO, MVFR ceilings are expected after midnight with medium confidence in extent and timing. If MVFR/IFR ceilings develop in the overnight hours, they are expected to lift by mid- morning. Breezy to gusty onshore flow will persist through the forecast period.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, VFR is expected to persist through the remainder of the afternoon evening with MVFR/IFR likely after sunset and not until after midnight at KSNS. Breezy onshore winds at times will persist through the forecast period.

Marine

(tonight through next Wednesday) Issued at 431 PM PDT Fri Jul 31 2026

Northwest winds increase to strong across the coastal waters with some pockets of fresh breezes right along the coastline. Northern coastal waters and the Big Sur coastal jet region will experience north-northwest strong to near gale winds with frequent gale force gusts through the weekend. In response to strengthening winds, moderate seas build to very rough (13-15 ft) in the Northern zones and rough (9-11 ft) in the Southern zones by Sunday and persist into Monday. Thereafter, seas gradually subside back to moderate (5-8 ft) by mid next week. Long period southerly swells persist in our coastal waters through the weekend.

Beaches

Issued at 1216 PM PDT Thu Jul 30 2026

Long period southerly to southwesterly swell of 14-17 seconds continues to impact our coastline through at least Saturday afternoon, bringing hazardous beach conditions to the Central Coast and the San Francisco Bay Area. Sneaker waves and strong rip currents will be the primary threats, with breaking waves up to 10 feet along some south and southwest facing beaches and break points, such as Santa Cruz, Pacifica, and parts of Stinson or Ocean Beach. This can be particularly surprising when wave heights increase suddenly after a period of seemingly tranquil wave action. In fact, sneaker waves can have 20+ minutes in between the larger sets (breaking waves) with significant "flat/calm looking" times between them. Due to the long period, sneaker waves are powerful and can catch beachgoers by surprise, resulting in people and pets being swept into the cold, turbulent ocean. Rip currents are strong enough to pull even the strongest swimmers away from shore. Check marine conditions before you head out! Swim near a lifeguard, if possible. Maintain a safe distance from the water, and stay away from jetties, piers, beachside rocks, and other waterside infrastructure. Never turn your back to the ocean and if you have small children or pets at the beach, please keep an eye on them.

Watches, Warnings, Advisories

Ca, Beach Hazards Statement through Saturday afternoon for CAZ006- 505-509-529-530.

PZ, Small Craft Advisory until 9 AM PDT Saturday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.

Gale Warning from 9 AM Saturday to 9 PM PDT Sunday for Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory until 5 AM PDT Sunday for Pt Reyes to Pigeon Pt 0-10 nm.

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

Small Craft Advisory from 9 AM Saturday to 5 AM PDT Sunday for Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory until 3 PM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Gale Warning from 3 PM to 9 PM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm.

Gale Warning from 9 AM Saturday to 3 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM.

Small Craft Advisory until 3 AM PDT Monday for Pigeon Pt to Pt Pinos 10-60 NM.

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