Issued at 927 PM PDT Sat Oct 18 2025
The forecast was updated to include coastal fog for tonight and Sunday morning. Microphysics satellite imagery shows areas of fog and very low clouds over the coastal waters. The southern coastal waters fog and very low clouds are converging with fog caught up in a southerly wind reversal along the Monterey County coastline. At 9 pm the SMX-SFO pressure gradient was 1.2 mb, however the SFO-SBA gradient was northerly at 0.7 mb. Fog within the shallow marine layer will result in surface visibilities at or below 1/2 mile, including dense fog at less than 1/4 mile visibility. Fog will enter in the Salinas Valley, while also moving northward along the coastline tonight and Sunday morning. The High Resolution Rapid Refresh (HRRR) model is showing some of the pressure gradient from SMX to SFO tonight, but shows the gradient reversing Sunday. Similarly the NAM model is showing a weak northerly pressure gradient Sunday. Tough to say at this point if the current southerly wind reversal is, at the synoptic scale, connected to the upper low (its surface ridge) ~ 700 miles south-southwest of Monterey or independent from the upper low and due to smaller scale ridging on the Central Coast or if both are influencing the surface gradient; not all the time, but model forecasts are sometimes late forecasting the onset of SMX-SFO, SBA-SFO i.e. southerly pressure gradients.
On the subject of complex short term weather, at one point during the late afternoon across a 5 mile span from KMRY Airport to Pebble Beach/Carmel we had a large (20F) dewpoint temperature difference, upper 30s at KMRY, upper 50s Pebble Beach/Carmel while there was 10F air temp difference. Similar elevations had very different water vapor differences over a short distance, both typically evenly maritime influenced. The dryness (dewpoint temps upper 30s) was real at KMRY, stepping outside to observe the weather earlier you could feel the distinct dryness in the air. Interesting to attain a difference like that given the relative weakness of the SMX-SFO gradient and air temps just above sea level in the lower level temperature inversion (lower 70s).
The 00z October 19th GFS is coming in and showing similar output to previous global output: strong to even stronger zonal 200 mb jet stream winds cross the North Pacific reaching the West Coast through the week, resulting in an increasing chance of rain here in our forecast area later in the upcoming week and weekend. Instability and low pressure /wave/ development accompanies strong wind shear in the jet stream, pulling in a fair amount of water vapor for rain development including in our forecast area late next week and weekend. The northern hemispheric pattern remains winter-like, very energetic with a number of long wave troughs. We've had quite a strong (early) start to our rain season and water year with two months to go to reaching the winter solstice.
For additional information on the forecast please see the previous discussions.
, Issued at 218 PM PDT Sat Oct 18 2025 (This evening through Sunday)
High pressure and ridging have settled back in over the Bay Area and Central Coast and helped to warm temperatures up today with a cut- off low located to our southwest offshore of Southern California. Warmer temperatures will continue again on Sunday with highs in the mid 70s to low 80s across the interior and in the 60s to low 70s along the coastline. Morning low temperatures are forecasted to be in the low to mid 50s for the Bay Area and Central Coast, excluding the far interior Central Coast where low temperatures will be in the 40s. Now the caveat to this forecast ties into our next point, light offshore winds continue Saturday night into Sunday. Offshore winds typically bring in drier air which can reduce cloud cover and mitigate fog development. As a result, fog is not anticipated to develop tonight. The lack of cloud cover, however, may have an additional side effect on our forecast, specifically on the forecast accuracy of our low temperatures. This morning the Santa Rosa Airport was forecast to reach a low of 50 degrees Fahrenheit. It actually reached a low temperature of 45 degrees Fahrenheit thanks to increased radiational cooling caused by the lack of cloud cover. This phenomena was observed in the interior Central Coast was well where some of the highest ridgetops saw low temperatures in the upper 30s to low 40s this morning (forecasted to be in the mid to upper 40s). It is possible that, given the lack of fog and lack of cloud cover forecasted overnight, we may see additional radiational cooling tonight with temperatures dropping lower than what is currently in the forecast. This would most likely impact the North Bay Valleys and portions of the interior Central Coast. Otherwise, an overall pleasant weekend continues with the potential for unsettled weather to return late next week.
A Beach Hazards Statement remains in effect through 11PM tonight due to an increased risk for sneaker waves and rip currents. Further information can found in the Beaches section below.
..issued at 218 PM PDT Sat Oct 18 2025 (Sunday night through next Friday)
Upper level ridging and high pressure continue into early next week, keeping the forecast relatively stable through Tuesday. High temperatures will be in the 70s to low 80s across the interior and 60s to low 70s along the coastline. Offshore winds briefly strengthen across the higher elevations of the North Bay Interior Mountains Sunday night into Monday morning. This will result in locally drier conditions during the day on Monday and overnight Monday into Tuesday across the elevated terrain. Fire weather concerns remain low given recent wetting rains and moist fuels across the region. The pattern begins to change Tuesday as the cut- off low offshore of Southern California merges with an upper level trough and moves into California late Tuesday into Wednesday. This is a dry system so we aren't expecting any rain from it, but, it will bring noticeably cooler temperatures beginning Wednesday. High temperatures across the interior will drop into the 60s to low 70s and stay in the 60s along the coastline. Overnight lows will cool as well with low temperatures in the mid 40s to mid 50s expected.
Now for the interesting portion of the forecast: unsettled weather looks to return Friday and remains unsettled into the weekend. Model guidance continues to indicate a potentially significant atmospheric river moving into the West Coast October 25th-27th. Confidence is increasing that we will see rain across the Bay Area and Central Coast with potentially heavy rain across portions of the North Bay starting late Thursday into Friday. The CPC maintains a moderate risk of heavy precipitation and high winds over the North Bay and a slight risk of heavy precipitation and high winds over the rest of the Bay Area and Central Coast through the remainder of the weekend (Saturday and Sunday). Given that this system is just under a week out, it is still to early to discuss any forecast QPF totals or the precise timing of this system as models are still coming into consensus. Given the pleasant weather expected this weekend into next week, now would be a good time to make sure gutters are cleared out and any outdoors objects are secured ahead of this system.
(06z TAFS) Issued at 951 PM PDT Sat Oct 18 2025
LIFR CIGS are building along the coast, affecting the Monterey Bay terminals and approaching HAF later into the night. Winds become light overnight with LIFR and IFR CIGS forming at OAK and STS into early Sunday. MRY and STS look to be affected by patches of fog and mist, leading to poorer visibilities. CIGs clear and and visibilities improve into the late morning for most, with HAF scattering in the mid afternoon. Winds increase becoming more moderate for Sunday afternoon with only a few more breezy areas along the coast. Winds become light again into Sunday evening as low CIGs form around the Monterey Bay.
Vicinity of SFO, VFR through the TAF period. Light west winds last into the early morning on Sunday before becoming lighter and more variable as low clouds form near the terminal. These clouds erode into the late morning as west winds return. These winds increase into the afternoon, becoming moderate through the evening, but become light and variable again into Sunday night.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Cloud cover is filling around the bay with LIFR CIGs at the terminals. Expect some reductions in visibilities with these CIGs and further reductions at MRY into early Sunday. CIGs erode into the late morning as moderate winds return. Winds reduce again into Sunday night with low CIGs returning.
(tonight through next Friday) Issued at 951 PM PDT Sat Oct 18 2025
A moderate NW breeze and a moderate-rough NW swell will continue across the coastal waters today. Stronger winds will arrive Sunday, although the swell will gradually abate. By Sunday night, a new NW swell will move in, combining with the wind waves to build very rough conditions across the exposed coastal waters.
Issued at 106 AM PDT Sat Oct 18 2025
A Beach Hazards Statement is in effect through 11 PM tonight as a long-period swell impacts the Pacific coast. The San Francisco and Point Arena buoys have begun reporting swell periods of 19 seconds. The long-period swell increases the risk of sneaker waves and rip currents across the Pacific coast, potentially catching unaware swimmers off-guard. Never turn your back to the ocean! Swim near a lifeguard if possible! If caught in a rip current, swim parallel to shore until you escape its influence.
Beyond the expiration of the Beach Hazards Statement, another long period swell arrives in the early part of next week with a Beach Hazards Statement or a High Surf Advisory possible depending on how the forecast evolves.
Ca, Beach Hazards Statement until 11 PM PDT this evening for CAZ006- 505-509-529-530.
PZ, Small Craft Advisory from 9 AM Sunday to 9 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 3 PM Sunday to 9 AM PDT Monday for Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory from 9 AM Sunday to 3 PM PDT Monday for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 3 PM Sunday to 3 PM PDT Monday for Pigeon Pt to Pt Pinos 10-60 NM.
