textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 245 AM PST Wed Jan 21 2026

- Late night and morning fog across the North and East Bay Valleys

- Light rain across the Santa Lucia Range and portions of the Central Coast late Wednesday into Thursday

- Seasonal temperatures and dry conditions Friday into next week

SHORT TERM

Issued at 245 AM PST Wed Jan 21 2026 (Today and tonight)

High clouds are currently obscuring lower level fog development but a few reports have started trickling in from the East Bay in Byron and Concord. As of 2AM, Byron is reporting less than 1/4SM visibility and fog while the Concord Airport is reported 1/4SM visibility and fog. There are some signs of fog developing in the North Bay Valleys with the Santa Rosa Airport reporting low clouds and 1SM visibility. Fog coverage tonight should be similar to last night with patchy, locally dense fog expected in the North and East Bay Valleys. Early morning commuters in these areas should allow extra time to reach their destination and be prepared for sudden changes in visibility.

The upper level ridge that has been dominating our forecast for the last few weeks will be replaced by a cut-off low moving southwards down the California coastline today. The cut-off low will bring a few notable changes to our weather. The first is temperatures across the interior will return to cooler, more seasonal values with highs in the upper 50s to low 60s across the region. Morning low temperatures are expected to be in the low 40s to upper 40s with the higher elevations remaining in the upper 40s to low 50s.

The second change will be increased rain chances late Wednesday into Thursday for the Central Coast. High resolution models are showing isolated showers starting late this evening into Thursday morning across the Santa Lucia Range, the Monterey Peninsula, and portions of interior San Benito County. Now, if any rain is able to make it to the surface, any precipitation totals are expected to be low. The current forecast grids show less than 0.10" of accumulated precipitation across the Central Coast. 90th Percentile NBM guidance (a reasonable "worst case" scenario) shows between 0.1-0.35" across the Central Coast with the max in the Santa Lucia Range. While showers are most likely to impact the Central Coast, we may see a few isolated showers as far north as Santa Cruz County and the South Bay. The NBM places a less than 5% chance of thunderstorms across southern coastal Monterey County with atmospheric conditions looking unfavorable for thunderstorm development. Models do show between 100- 300 J/kg of most unstable CAPE but thunderstorm potential is limited by poor moisture, poor shear, and poor 700-500mb lapse rates. The most likely scenario is that we will see isolated showers across the Central Coast, predominantly in the Santa Lucia Range, with the potential for isolated showers to drift towards the South Bay on Thursday.

LONG TERM

Issued at 245 AM PST Wed Jan 21 2026 (Thursday through Tuesday)

Isolated showers continue across the Central Coast through Thursday morning before dry weather returns. By late Thursday, the cut-off low will be to our southeast (offshore of San Diego and Baja California) where it will move inland and be absorbed into upper level troughing across the interior U.S. late Friday into early Saturday. Upper level ridging then rebuilds across the western U.S. through the remainder of the long term forecast. Widespread fog potential decreases by late this week as a shallow marine layer (approx. 1000 ft) is able to redevelop as the cut-off low moves through. Overcast conditions are still likely as low level stratus and the shallow marine layer rebuild across the region.

High temperatures remain seasonal in the upper 50s to low 60s while portions of the interior Central Coast linger in the low to mid 60s. Morning low temperatures trend cooler starting Thursday with lows dropping from the 40s on Thursday to upper 30s to low 40s by Saturday. Sunday to Tuesday mornings look to be the coldest with lows dropping into the mid 30s to low 40s across the interior. Locally gustier offshore winds develop across the interior North Bay Saturday. Probabilistic guidance shows a 30-40% chance of gusts greater than 30 mph across the North Bay Interior Mountains. This drops to a 10-25% chance across only the highest peaks when looking at the probability of gusts greater than 40 mph. While this is a gustier offshore wind event, it should generally stay limited to the higher terrain.

In the very long term, models continue to indicate a chance for widespread precipitation to return late January into early February. The CPC 8-14 day outlook shows a slight chance for above normal precipitation along coastal Sonoma and Marin Counties with near normal precipitation expected for the rest of the Bay Area and Central Coast. Models will come into better agreement as to the timing and intensity of any future systems as we get closer in time to late January so stay tuned to the forecast to see how this shapes up in real time.

AVIATION

(12Z TAFS) Issued at 318 AM PST Wed Jan 21 2026

Patchy fog /LIFR-IFR/ this morning otherwise VFR today and tonight. A few showers developing tonight and Thursday morning.

Vicinity of SFO...VFR. Mainly light wind.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR. A few showers tonight and Thursday morning. Mainly light winds.

MARINE

(Today through Monday) Issued at 245 AM PST Wed Jan 21 2026

Gentle to moderate northerly breezes and moderate seas will continue through Thursday. On Friday winds will increase to a fresh northerly breeze along with building rough seas. Conditions will improve over the weekend as a light to gentle breeze settles in and seas gradually subside to slight Sunday through Monday.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.