, Issued at 1225 PM PST Tue Jan 20 2026 (This evening through Wednesday)
Fog continues to gradually dissipate across the region as mid/upper level moisture continues to lift northward. While the cloud shield is expansive, examination of our morning sounding and aircraft sounding data from SFO reveals that the low levels remain quite parched. What this translates to is high confidence that widespread rainfall is unlikely over the short term.
The primary hazard in the short term will be the re-development of fog, largely across the North and East Bay. While mid-level ridging remains in place across the area, surface flow will gradually become more southerly which may support more in the way of onshore flow. At a minimum, this should promote fog development in the favored spots of the North and East Bay, if not give us a higher chance. In fact some of the higher resolution model guidance advertises a repeat of fog across the US HWY 101 corridor across Sonoma County, similar to today.
..issued at 1225 PM PST Tue Jan 20 2026 (Wednesday night through next Monday)
While general mid/upper level ridging will equate to a largely "quiet" long term forecast period, there will be some brief shifts in the main upper pattern (in addition to morning fog). These shifts will offer slight changes in the day to day sensible weather elements. Late Wednesday into Thursday, model guidance is a bit more honed in on the exact track of an upper low forecast to intensify and move eastward through Southern California. This will induce upslope flow across the higher terrain of the Central Coast. While moistening will transpire, it doesn't appear that the column will completely saturate for a prolonged period of time. In addition, the speed of this upper trough will mean a low residence time across our area. At this time, there doesn't appear to be a significant amount of spread in the track of this feature so confidence is high that overall rain amounts will remain on the light side through Thursday night. In fact, some of the higher end scenarios (90th percentile) paint up to a tenth of an inch of rainfall for this event.
By Friday evening/Saturday morning the main upper low will kick eastward. In the wake of this system, a more defined push of offshore winds is anticipated. At this juncture, the potential for winds above 35 mph is under 10%, though it may be a little higher across some of the favored gaps and passes. The story will be a little different across the marine zones as the surface pressure gradient does tighten. In fact 925mb flow does ramp up here to around 35 knots (40 mph) across Pacific waters west of Marin/Sonoma counties.
Beyond day 7, model guidance remains largely consistent with broad ridging remaining in place. At times, however, storm systems may attempt to dampen out the amplitude of the ridge and place our region within a more zonal pattern. Some of the ensemble guidance systems remain aggressive with rainfall above 1/2." While the upper air pattern depiction is largely similar from ensemble suite to ensemble suite, the spread among individual systems (e.g., EPS) remains rather high as the spread ranges from no rain to three inches of rain in some locales. As always, we'll continue to monitor, message, and adjust as necessary.
(18z TAFS) Issued at 1112 AM PST Tue Jan 20 2026
LIFR vis due to valley fog is showing signs of lifting at KSTS with VFR expected to prevail through the remainder of the after noon and evening, with valley fog/Tule Fog expected to fill back in over the North Bay terminal later this evening into the overnight hours. VFR is expected to prevail through the remainder of the forecast period for Bay Area and Monterey Bay terminals.
Vicinity of SFO, VFR is expected to prevail through the remainder of the forecast period. A transition from weak offshore flow to weak onshore flow (potential for stratus/fog) returns late in the forecast period.
SFO Bridge Approach, Similar SFO.
Monterey Bay Terminals, VFR is expected to prevail through the forecast period with weak offshore flow limiting low stratus development.
(today through Sunday) Issued at 1112 AM PST Tue Jan 20 2026
Gentle to moderate northerly breezes continue across the waters through Wednesday. Winds increase later this week to a strong breeze by Friday. A weak storm system over the eastern Pacific will result in moderate northwest swell, promoting rough seas across the northern outer waters on Friday into the weekend.
Ca, None. PZ, None.
