Issued at 902 PM PDT Wed Sep 16 2026
The advertised cooldown for today definitely verified. Not only did highs remain well below seasonal averages they also came in under forecast values as well. Max temps reached the 60s along the coast and 70s inland with a handful of 80s well interior. Cold upper low coming down the coast, strong onshore flow, and lingering stratus clouds contributed to the cooler temps.
For this evening, stratus is already making an appearance across the region. Expect coverage to increase overnight. That being said, this is not a "classic" marine layer setup thanks to the nearby upper low. Definitely some strato-cu vibes as inland clouds are popping off over terrain features. No update is needed to the forecast this evening.
Thursday AM is still on track to start off cool, damp, and cloudy with drizzle.
, Issued at 110 PM PDT Wed Sep 16 2026 (This evening through Thursday night)
The marine layer was measured to be 2,400 feet deep by the 12Z sounding from Oakland. Surface observations show it's closer to 3,000 feet deep along the Central Coast, where all of Santa Cruz County remains under overcast skies. The NW wind direction created some downslope dry air that managed to keep Silicon Valley clear, but that was the exception. The morning stratus reached inland to Healdsburg, Dublin, and Paso Robles. As a cut-off low over Northern California continues to drift south, the marine layer will expand over the next 24 hours. The deeper cloud layer will be enhanced by some 700 mb vorticity and typical orographic lift to support some drizzle overnight through Thursday morning. The signal is better over the Bay Area than the Central Coast, but all of the typical drizzle locations have a chance. In fact, all 50 of the ECMWF ensemble members have some precipitation reaching SFO Thursday morning. This is still drizzle though, so the accumulation will range from a trace to a few hundredths before the atmosphere mixes in some drier air by midday.
In addition to drizzle, the cut-off low will bring some strong onshore winds this evening. The SJSU 2km WRF ensemble shows high confidence in a onshore 8-10 mb SFO-WMC gradient developing quickly this afternoon. This is a result of northerly winds west of the low cooling the coast, while warm southerly winds east of the cut-off support thermal exhaust and surface low pressure over northern Nevada. The RRFS shows gusts up to 40 mph this evening in favored gaps such as Pacheco Pass, Altamont Pass, and the Carquinez Straight. Gusts up to 25 mph are likely in both the San Francisco and Monterey Bays later today as well. These winds will peak in the early evening, but continue well into the overnight hours. The strongest winds are not widespread enough to warrant a wind advisory, but expect to feel them while driving through the areas mentioned.
Outside of drizzle and wind, the cut-off low will bring cool, humid conditions to the entire Bay Area. Coastal temperatures will be in the 60s along the coast and 70s inland. Some of the warmer places will reach the upper 70s, but that's still roughly 10 degrees cooler than normal for this time of year. We'll get a repeat of these cool temperatures on Thursday before a slight warming trend kicks off Friday.
..issued at 110 PM PDT Wed Sep 16 2026 (Friday through next Tuesday)
The cut-off low will have weakened and start to be reabsorbed into the jet stream by Friday. This will open the door for a short wave ridge to briefly build through Saturday. While short lived, this feature will cause the marine layer to compress and temperatures to return back to normal. We may even see some weak offshore winds at this time. The SFO-WMC gradient is expected to flip negative by Saturday morning, but there is no indication it will be very strong. By Sunday a much weaker cut-off low will move in from the west. This feature will likely keep conditions pretty consistent and relatively benign through mid week. The 850 mb temperature is expected to hover around 20C early next week, which is around the 75th percentile for this time of year. By mid week the uncertainty balloons. Since the pattern depends on multiple, hard to track cut-off lows, chaos theory goes into full swing quickly. Ensembles shows an equal chance of 850 temps reaching 5C or 25C next Thursday, which literally spans the entire range of historical possibilities for this time of year. While I like to look for signs of early rain or strong offshore winds this time of year, with the high uncertainty it's not really
(00z TAFS) Issued at 601 PM PDT Wed Sep 16 2026
A mixed bag of MVFR to VFR conditions persists across our region. VFR conditions are not expected to last for long as current satellite imagery shows stratus beginning to form near the North Bay coastline. As we approach sunset, the stratus will become more uniform and push into the Bay Area given the onshore flow support, thus resulting in widespread MVFR conditions tonight. Monterey Bay follows shortly after Bay Area terminals. Low to medium confidence on MVFR ceilings reaching SJC and LVK overnight as the upper-level low pressure passes overhead and lifts ceiling heights right above criteria in the interior valleys. The 00Z OAK sounding measured the top of the marine layer around 3100 feet, thereby indicating widespread MVFR to borderline MVFR-VFR ceilings tonight. The synoptic set up also supports the potential for drizzle across Bay Area terminals, though confidence is too low to include in the TAF.
In terms of wind, gusty onshore breezes continue to impact APC, SFO, SJC, and LVK into the evening. Overnight, widespread southwest to southerly gentle breezes settle in before shifting back to the typical diurnal pattern Thursday morning.
Vicinity of SFO, Leaned on a pessimistic forecast this TAF cycle given that cloud ceilings are currently on the cusp of MVFR. They are expected to drop slightly overnight, keeping both OAK and SFO in MVFR territory. As the upper-level low moves east, ceilings are expected to gradually lift and scatter out by late Thursday morning with VFR prevailing through most of the day. Medium confidence on the exact clearing time tomorrow. Strong gusty onshore winds persist at SFO until the evening. Overnight, winds ease and become south- southwest which eventually shift back to westerly by Thursday afternoon.
SFO Bridge Approach, Similar to SFO with ceilings increasing in height south of the bridge overnight.
Monterey Bay Terminals, VFR with gentle to moderate west to southwesterly breezes. MVFR ceilings return around sunset and persist into late Thursday morning. Winds ease to light breezes and shift southerly overnight, but return to a west-northwest flow after stratus scatters out on Thursday. Medium to high confidence for ceilings to remain MVFR overnight.
(tonight through next Monday) Issued at 237 PM PDT Wed Sep 16 2026
Moderate northwest winds prevail across the outer waters with occasional fresh to strong gusts. Moderate westerly breezes dominate over the Bays with gusts up to 25 knots resulting in hazardous conditions for small crafts through this evening. Winds will decrease Thursday. By Friday, widespread northwest to north breezes increase to fresh with occasional strong gusts. Wind driven rough seas to 9 to 10 feet subside to moderate by the evening and will remain slight to moderate into the weekend.
Ca, None. PZ, None.
