, Issued at 952 AM PDT Sat Apr 25 2026 (This afternoon through Sunday)
An upper level low roughly 200 miles west of the Monterey Bay will approach the coast over the next 12 hours. This system is bringing widespread overcast skies, some very light rain, and cooler temperatures today. Below this upper level disturbance, we also have a deep marine layer impacting the surface conditions. The 12Z balloon measured the depth at nearly 4,000 feet capped by a very strong inversion. Between the moist marine layer and upper levels, there is a layer of very dry air between 800 mb and 600 mb, where the average relative humidity is less than 5%. This dry layer will cause much of the rain to evaporate before reaching the surface today. So far we've recorded 1/100th inch of rain in a few different rain gauges throughout the Bay Area and Central Coast. Rain will generally fall as light and brief showers, with the most activity expected in Santa Cruz and Monterey Counties early Sunday morning. All told, we're not expecting to exceed 1/10th of an inch. For Big Sur Marathon runners, this is the type of rain that's nice to run in. The wind will be much weaker than normal years, too.
Anytime there is a landfalling low pressure system we need to take a look at thunderstorm chances. There are a lot of factors working against convection in this environment. The CAPE isn't expected to break 100 J/kg, and even that is all below the inversion where the air is above freezing. That means there won't be any ice particles to create static electricity buildup. Additionally the inversion and very dry mid levels are barriers to coherent updrafts. While the NBM shows a 5% chance of thunderstorms today, that may be on the high side. Chances may be marginally better tomorrow as the dry layer becomes more saturated, but we're still well below 10%.
After the upper level front moves through Sunday, much drier air will filter in, clearing the mid and upper level clouds by Sunday afternoon. The marine layer rarely gets much deeper than 4,000 feet, and it's unlikely to survive as the low moves overhead. That should help mix out the low clouds as well. So the Sun should come out tomorrow, but the temperatures will still be stuck in the 60s until the 850 temps recover through the week.
..issued at 952 AM PDT Sat Apr 25 2026 (Sunday night through next Friday)
A warming and drying trend will start Monday and continue through the week as the 500 mb trough gradually transitions into a ridge. Temperatures will climb a few degrees each day, eventually reaching mid to upper 70s by Wednesday across the interior, and remaining there into the weekend. The marine layer will start to reform under the ridge, keeping coastal areas in the 60s through the week. In other words, it will be a pretty nice week. It's hard to say what will happen the following week, with ensemble clusters split roughly evenly on a continued ridging pattern or the return of another trough and unsettled weather.
(06z TAFS) Issued at 917 PM PDT Sat Apr 25 2026
500 mb low center exits to the east, while 500 mb troughing continues late tonight and Sunday. A weak surface cool front also moves in from the northwest late tonight and Sunday morning. VFR- MVFR remains in the forecast with a few areas of light drizzle and/or showers tonight and Sunday.
Vicinity of SFO, VFR-MVFR. A few showers developing tonight and Sunday morning. Southwest wind 5 to 10 knots tonight through Sunday morning then gusting to 20 knots Sunday afternoon and early evening.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR-MVFR. Light coastal drizzle and/or showers tonight and Sunday. Variable wind directions mainly less than 10 knots tonight and Sunday morning becoming westerly near 10 knots Sunday afternoon and early evening.
(tonight through next Friday) Issued at 913 PM PDT Sat Apr 25 2026
Moderate west to northwest breezes will continue through the middle of next week before increasing to a fresh to strong northwest breeze. These stronger winds will build rough seas of 8-10 feet in exposed waters.
Ca, None. PZ, None.
