, Issued at 1120 AM PDT Mon Sep 21 2026 (This afternoon through Tuesday)
The dominant weather feature today is a 500 mb cut-off low currently centered over Pt. Conception. The 500 mb height at Vandenberg was 5750m as measured from the 12Z sounding. This is just below the 10th percentile in the climatology for this time of year, so it's fairly notable, but not extreme. The result is cooler temperatures, a deeper marine layer, some morning drizzle, and even a few real raindrops. The marine layer was measured at 2,400 feet deep by the 12Z weather balloon from Oakland. This deeper cloud layer, combined with low-level vorticity and orographic lift allowed some coastal drizzle this morning. Drizzle was reported throughout the typical areas across the Bay Area and Central Coast. The La Honda RAWS in the Santa Cruz Mountains was the winner with 0.05" of precipitation recorded over the last 24 hours. This deep marine layer, high humidity and ample cloud cover will keep temperatures 5-10 degrees cooler than normal this afternoon.
The cut-off low will continue to slide NE over the next 24 hours, loosening its grip on the weather here. Tuesday will be a transition day as the marine layer starts to compress and temperatures increase back to normal.
..issued at 1120 AM PDT Mon Sep 21 2026 (Tuesday night through next Sunday)
The long term forecast is a little bit of a roller coaster, but like the kind for kids that doesn't do anything too scary. As the low continues to exit the area, the upper level pattern will gradually shift to a strong trough over the Gulf of Alaska and a ridge stretching from Texas to central Canada. By Wednesday the west coast will be in between these two features, with a small positive 500 mb height anomaly arriving Wednesday. While the 500 mb height anomaly is minor, the 850 temperature anomaly will climb to around 5-7C above normal Wednesday - Thursday. This will bring inland temperatures into the upper 80s to low 90s, with 70s along the coast both Wednesday and Thursday. There is some moderate HeatRisk associated with this event, but it's not widespread and has been trending down. With the longer nights, short duration, and continued onshore winds, we are not expecting a heat advisory with this event at this time. The trough over the Gulf of Alaska will move into the Pacific Northwest by Friday, reversing the warming trend and bringing temperatures back below normal for next weekend.
(00z TAFS) Issued at 457 PM PDT Mon Sep 21 2026
Marine layer remains entrenched along the coast and locally inland already as of 00z and will spread inland efficiently and early this evening with a trough over the region. Low cigs to linger at least through 18-19z Tuesday before mixing out.
Vicinity of SFO, Low cigs to push over the terminal early this evening, as early as 03z then linger at least through 18-19z Tuesday.
SFO Bridge Approach, Stays clear through around 04z before losing visuals through at least 17z Tuesday.
Monterey Bay Terminals, KMRY and KSNS already have ceilings and high confidence they continue at least through 18-19z Tuesday.
(today through Saturday) Issued at 1113 AM PDT Mon Sep 21 2026
The gradient between high pressure over the Pacific and lower pressure over California is supporting a moderate to strong NW breeze across the coastal waters. Winds are strongest north of Pt. Reyes. The stronger winds will move south to impact the majority of exposed waters over the next 36 hours. These winds will build rough seas, with significant wave height peaking at 10-12 feet Tuesday night. Conditions will gradually improve Wednesday through Thursday.
Ca, None. PZ, Small Craft Advisory until 5 AM PDT Wednesday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory from 3 PM to 9 PM PDT Tuesday for Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory from 3 PM Tuesday to 3 AM PDT Wednesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 3 PM Tuesday to 5 AM PDT Wednesday for Pigeon Pt to Pt Pinos 10-60 NM.
