Swell Matrix

Area Forecast Discussion

National Weather Service San Francisco CA

408 pm PDT Tue Oct 13 2026

Short Term

, Issued at 320 PM PDT Tue Oct 13 2026 (This evening through Wednesday night)

Water vapor imagery shows the upper level low over the Great Basin starting to move east this afternoon, with high pressure remaining over the Pacific. As a result, Northern California remains situated between the two, with dry northerly flow aloft. Despite the cooler start to the day, temperatures have warmed nicely today, with sunny skies prevailing. In fact, temperatures are running 3 to 6 degrees warmer than this time yesterday for most locations, with up to 10 degree warmer for North Bay areas, thanks to some light offshore flow. These warmer conditions will make for a pleasant evening across the region.

Expect one more cool fall like night tonight, as clear skies, dry conditions, and light winds aid in the radiative cooling. Most locations will fall into the 40s to lower 50s tonight, with fewer spots dipping into the 30s. That said, we will have some light offshore winds once again across the interior North Bay Mountains tonight. With weak offshore gradients and marginal upper level support (10-15 kts at 925 and 850 mbs), think gusts will mostly stay around 30 mph tonight. Some of the favored ridges, gaps or passes could be higher though.

Our warming trend will continue into Wednesday, as high pressure rebuilds into the region. Expect daytime temperatures to increase another 3 to 7 degrees tomorrow, with the greatest warming occuring across the inland areas. Also expect another round of offshore winds for Wednesday night to develop across the interior North Bay Mountains. There is a little better support this evening, as offshore gradients into to around 7 mbs, and 925 mb winds increase to 15 to 25 kts. Therefore, expect gusty conditions to develop once again across the favored exposed ridges, passes, and gaps. Palmer

Long Term

..issued at 320 PM PDT Tue Oct 13 2026 (Thursday through next Monday)

High pressure will continue to strength across the region, with our warming trend continuing through Friday. Daytime temperatures will warm a few degrees each day, with Friday likely being the peak of this heat event. While the warmest spots will stay in the 90s this time around, we will see a Moderate Heat Risk for some of our inland areas, thanks to the overnight temperatures will also warming a bit each night. We are also expecting one last push of offshore winds Thursday night into Friday. These push looks stronger than the previous two nights, with ever so slightly better upper level support. For now, think the winds will once again be limited to the exposed ridges, gaps, and passes, with gusts up to 40 mph possible. Some of the favored spots may see higher gusts, but those stronger gusts will be isolated at best.

Our ridge will start to flatten this weekend, with Saturday being the start of our cool down. It will still be warm through the weekend across the inland areas, just not as warmer as Friday.

The flattening of the ridge over the weekend opens the door for a trough to dig south from the Gulf of Alaska for early next week. At this point in time, the ensembles are in very good agreement with this trough digging along the West Coast, and bringing another round of cooler air to the region. The uncertainty comes with the strength and timing. For now, it does look strong enough to be us some gusty onshore winds and our first decent chance of widespread rain. While it doesn't look like much rain, there is a 10-30 percent chance of rain for Monday and Tuesday. Needless to say, this will bear watching. Palmer

Aviation

(00z TAFS) Issued at 408 PM PDT Tue Oct 13 2026

Generally VFR conditions prevail through the TAF period, with some high resolution models depicting patchy coastal stratus towards the end of the TAF period. Gentle to moderate northwest to north flow persists into the evening hours, with light winds overnight before the onshore winds resume Wednesday afternoon

Vicinity of SFO, VFR at the terminal through the TAF period. Gentle to moderate northwest flow will continue into the evening, with light offshore flow developing overnight into Wednesday morning before moderate northwest winds resume in the afternoon.

SFO Bridge Approach, Similar to SFO.

Monterey Bay Terminals, Moderate to high confidence of VFR through the TAF period. Gentle to moderate northwest winds prevail through the evening hours, with light drainage winds overnight before gentle to moderate northwest winds resume Wednesday afternoon.

Marine

(tonight through next Sunday) Issued at 408 PM PDT Tue Oct 13 2026

Strong northwesterly gusts are expected nearshore from Pigeon Point to Point Pinos and the Monterey Bay through this evening. Otherwise, gentle to fresh northerly breezes will continue through the remainder of the week with an improving seas state through Wednesday. Long period southerly swell will also continue through midweek with some gradual easing by the end of the week.

Watches, Warnings, Advisories

Ca, Coastal Flood Advisory until 4 PM PDT Wednesday for CAZ506.

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

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