San Francisco’s weather may take a nasty turn this week

Bay Area residents face foggy mornings and significant rainfall arriving Tuesday through Wednesday

San Francisco residents woke up Sunday morning to familiar gray skies and patchy fog blanketing low-lying neighborhoods as temperatures hovered around 51 degrees.

Reduced visibility near dawn created challenging conditions for early commuters, requiring extra caution and additional travel time for those navigating the city’s streets and highways.

The murky start to the day represents just the beginning of a dynamic weather pattern that will transform conditions across the Bay Area by midweek.

While Sunday offers some reprieve with improving afternoon conditions, a more substantial weather system looms on the horizon, promising to deliver the wettest stretch the region has seen in recent days.

Sunday’s improving conditions provide brief window

The morning fog is not expected to linger throughout the day.

Patchy low clouds should thin out by mid to late morning, allowing partly sunny skies to emerge with high temperatures reaching near 64 degrees.

By later afternoon, readings will settle back into the low 60s as the marine layer reasserts its influence over coastal areas.

West winds will strengthen to between 6 and 12 mph, creating noticeably breezier conditions on exposed hilltops and bridge approaches throughout the afternoon.

Despite the wind pickup, most of the day after the late-morning commute looks dry and suitable for outdoor activities.

Overnight fog returns before rain arrives

Sunday night brings the return of low clouds and fog between approximately 11 p.m. and 5 a.m., with overnight lows near 51 degrees.

North Bay areas face a 20 to 40 percent chance of light rain late Sunday night.

Locations south of the North Bay have much lower odds of receiving anything beyond light drizzle.

This isolated precipitation represents an appetizer for what approaches Tuesday.

A stronger weather system is expected to roll into the Bay Area from Tuesday afternoon through Wednesday.

Midweek system brings heaviest rainfall

Showers accompanied by a slight chance of thunderstorms are expected from Tuesday night into Wednesday morning.

New rainfall totals could range from a quarter to a half inch in many locations.

Coastal areas and higher terrain are favored for the higher amounts within that range.

Snow levels are forecast to fall toward approximately 5,000 feet.

This may bring wintry precipitation to the highest peaks in the Bay Area’s mountain ranges.

The lowering snow level reflects the cooler air mass associated with this system.

According to the National Weather Service San Francisco, confidence is growing that midweek will deliver the wettest conditions over the next several days.

Marine conditions deteriorate significantly

Boaters face building seas and Small Craft Advisories around exposed coastal waters as the system approaches.

Ferry crossings may turn choppy during the heaviest precipitation periods.

Anyone planning maritime activities should check the latest marine forecasts before leaving harbor.

The combination of increased wave heights, gusty winds and reduced visibility creates challenging conditions for maritime operations.

Preparing for the weather transition

Residents should keep a light rain jacket readily accessible as the wetter pattern develops.

Those planning beach outings may want to consider shifting plans inland.

Morning commuters should allow extra time when fog reduces visibility.

Foggy mornings combined with wet roadways by midweek demand extra attention and defensive driving.

Source: National Weather Service San Francisco / Tony Ng