, Issued at 1056 AM PDT Sun Sep 13 2026 (This afternoon through Monday)
Troughing continues to dominate the forecast as a deep upper level low continues to move through the PNW and into the Intermountain West. The marine layer remains at a depth of approximately 1500 ft but dry air in the wake of last night's dry cold frontal passage prevented stratus from redeveloping across the interior last night. The drier airmass is expected to remain in place through at least midweek with another night of largely clear skies expected tonight. Patchy stratus is possible directly along the coastline where conditions are more supportive for stratus development. Wondering why? Buoys are reporting warmer ocean temperatures than air temperatures above it. This indicates an upwards transfer of heat/moisture from the ocean to the air, resulting in a warming and saturating layer of air where stratus is able to develop. Any coastal stratus that does develop will be patchier with the San Mateo coastline and coastal Monterey Peninsula the most likely areas to see at least temporary cloud cover overnight.
Another factor in tonight's stratus forecast is the wind. Winds through this evening will be breezy and onshore with the SFO-WMC gradient forecast to peak around +9 to +10 mb today. This largely correlates to wind gusts between 20 to 35 mph with gusts up to 45 mph across the favored windy spots. By tonight the wind setup changes from onshore to offshore. Offshore winds should remain on the lighter but two locations, the highest ridgelines of the Vaca Mountains and the Altamont Pass, will experience gustier offshore winds between 20 to 35 mph overnight tonight through Monday. Offshore winds will keep the region slightly drier overnight which increases confidence that stratus will struggle to redevelop/spread across the interior tonight. That being said, not anticipating any major fire weather concerns given the short duration and localized nature of the stronger offshore.
A slight warming trend will kick off Monday as the center of the upper low moves into the Intermountain West and more zonal flow dominates Central California. This will see a return of near normal temperatures for much of the region with interior highs in the 80s and coastal areas in the 60s to 70s. The hottest locations (far interior East Bay and interior Central Coast) will reach the upper 80s to potentially the 90 degree mark. Winds to decrease throughout the day with light to moderate onshore winds returning during the day.
..issued at 1056 AM PDT Sun Sep 13 2026 (Monday night through next Saturday)
Zonal flow to slight troughing continues through midweek before another deeper trough pushes into the Oregon and Northern California border. Temperatures remain relatively seasonal on Tuesday with highs in the upper 70s to 80s across the interior and 60s along the coastline. The arrival of the upper level trough will bring a cooler airmass into the Bay Area and Central Coast with 850 mb temperatures peaking around 12 C during the day. That is roughly between the 10th and 25th percentiles for this time of year with the median 850 mb temperature ~17 C. The NBM was running a bit warmer than other models for Wednesday/Thursday but the latest run has started to lower temperatures, coming into better agreement. A reasonable lower end temperature forecast for Wed/Thurs would be interior highs in the low to mid 70s while the higher end forecast (the current forecast) keeps high temperatures in the mid 70s to low 80s. Given the arrival of the much cooler airmass, would not be surprised if we saw the forecast high temperatures for Wed/Thurs to decrease by a few more degrees (slightly closer to the lower end forecast). The caveat to this being temperatures may be warmer if the trough/cold air mass slows down and arrives later than currently forecast. Regardless, the cool down will be most evident Wednesday and Thursday with near normal temperatures in the upper 70s to mid 80s Friday into the weekend. The arrival of the trough should allow the marine layer to deepen enough that stratus will become more widespread mid to late week. Diurnally breezy winds continue across mountain gaps and passes, the coast, and along the highest ridgelines. Northern California and the Sierra Range have some potential for thunderstorms mid to late week as the trough moves in but chances are negligible across our region (<5%) with thunderstorms not expected.
(18z TAFS) Issued at 1023 AM PDT Sun Sep 13 2026
VFR conditions persist at most terminals this morning except for patchy coastal stratus along the San Mateo County coastline. Onshore winds increase late this morning and will mix out the stratus. These stronger winds will prevail through the evening before easing into the night and into Monday morning. There is moderate confidence for stratus to return to the coast late tonight into early Monday morning. Any stratus that does develop with dissipate by late Monday morning with increasing onshore winds by the afternoon.
Vicinity of SFO, VFR. Northwesterly winds increase throughout the morning and into the afternoon with gusts up to 33 kt expected. Winds ease late in the night with some offshore wind potential early Monday morning before returning to onshore by mid- to-late morning.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR. Northwesterly winds increase throughout the morning and into the afternoon with gusts up to around 25 kt. Winds ease after sunset and potentially become variable early Monday morning. There is also moderate confidence for IFR-MVFR conditions to develop early Monday morning.
(today through Friday) Issued at 858 AM PDT Sun Sep 13 2026
Hazardous conditions for small craft prevail through the middle of the week. Northwest winds strengthen through tonight with gale force gusts across the southern inner coastal waters and the Monterey Bay. A few gale force gusts are possible across the northern inner coastal waters. Winds will remain elevated through midweek before diminishing late week. Moderate seas will build to between 8 and 10 feet and become rough by Monday in response to the stronger winds.
Ca, None. PZ, Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for SF Bay N of Bay Bridge.
Small Craft Advisory until 3 PM PDT this afternoon for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm.
Gale Warning from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay-Pigeon Pt to Pt Pinos 0-10 nm.
Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory from 3 PM Monday to 3 AM PDT Tuesday for Pt Arena to Pt Reyes 0-10 nm.
Gale Warning until 3 AM PDT Monday for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 3 PM this afternoon to 3 AM PDT Tuesday for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory until 3 AM PDT Tuesday for Pigeon Pt to Pt Pinos 10-60 NM.
