textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1237 PM PDT Mon Apr 6 2026

- Cooler seasonal to slightly below normal temperatures this week

- Beneficial rain arrives midweek and lasts into the weekend

- Slight chances for thunderstorms Thursday and Friday afternoon

SHORT TERM

Issued at 1237 PM PDT Mon Apr 6 2026 (This evening through Tuesday)

The marine layer redeveloped overnight with widespread stratus observed across the Bay Area and Central Coast due to a weak shortwave trough moving into California. We are still looking at cooler temperatures today with highs in the low to mid 70s across the interior and 60s closer to the coast. Light, onshore winds continue with locally breezier conditions across the higher elevations and mountain gaps/passes. Widespread stratus is expected again tonight with the marine layer deepening to around 1500 ft. Most of the Bay Area and coastal Central Coast can expect to wake up to overcast conditions again with patchy fog possible in the North Bay and South Bay Valleys. Clearing times tomorrow will be similar to today with stratus coverage gradually dissipating over the course of the morning. High temperatures linger in the 70s across the interior and 60s along the coastline again on Tuesday. Shortwave ridging briefly builds in during the day on Tuesday before the ridge quickly progresses eastward Wednesday. Stratus returns Tuesday Night but shortwave ridging will start to compress the marine layer and keep stratus confined closer to the coast.

LONG TERM

Issued at 1237 PM PDT Mon Apr 6 2026 (Tuesday night through next Sunday)

Brief shortwave ridging Tuesday into Wednesday will allow temperatures to warm slightly on Wednesday but only by a few degrees. High temperatures will be in the mid to upper 70s across the interior, low 80s across the interior Central Coast, and in the 60s along the coast. This will be short lived as our promised cool down truly begins Thursday and continues into the weekend. A deep upper level cut-off low will approach the West Coast on Wednesday and will push Tuesday's shortwave ridge eastward. This low pressure system is a cold core low from the Gulf of Alaska and is bringing a cooler air mass (850 mb temperatures around 6-8C) with it. The mean 850mb temperature for early to mid April is around 7-8C so this colder air mass is really only bringing us back to more seasonal temperatures. We do continue to see colder air being advected in over the weekend with 850 mb temperatures dropping to around 0-1C. This would be around the 10th percentile for 850mb temperatures for this time of year and signals below normal surface temperatures are more likely. What does that mean at the surface? Temperatures will first cool to more seasonal values on Thursday with highs in the 60s to low 70s. Friday into the weekend, high temperatures become seasonably cool in the 60s with most spots running around 2 to 5 degrees below normal. Overnight low temperatures will also experience a cooling trend with lows gradually cooling from the 50s to mid to low 40s. Portions of the interior Central Coast may see low temperatures dropping into the upper 30s starting Sunday.

Temperatures are only part of our weather change up, however, so now we turn to the much anticipated precipitation forecast for the upcoming week. As our cut-off low arrives, it will bring a fairly persistent stream of moisture with it. PWAT values are around 0.8- 0.9" with the slow movement of the low southwards along the California coast keeping the moisture training over the Bay Area/Central Coast. Coastal drizzle becomes more likely Wednesday night into Thursday morning with scattered showers moving in throughout the day on Thursday. Showers then continue through the weekend thanks to the slow movement of the low. Precipitation totals have increased slightly with most of the lower elevations seeing between 0.25-0.35" of precipitation. The higher elevations remain the big winners with up to 0.75" of rain expected. The highest peaks of the Santa Cruz Mountains and the Santa Lucia Range will see anywhere from an inch to an inch and a half of rain. Rainfall remains beneficial and is helping to reduce near term fire concerns. Locally gusty winds are expected directly along the coastline and across the higher elevations but conditions are not forecast to meet Wind Advisory criteria.

Thunderstorms are still possible Thursday afternoon and again Friday afternoon. The setup now looks more favorable for thunderstorms on Friday (20-25%) rather than on Thursday (10-15%). MUCAPE values still look good but low level shear remains minimal. If any thunderstorms do develop the most likely hazards would be locally heavy rain, gusty winds, and the potential for small hail.

AVIATION

(18Z TAFS) Issued at 1129 AM PDT Mon Apr 6 2026

The marine layer made a triumphant return last night and will remain the most important feature for aviation weather over the next few days. The current marine layer depth is around 1500 feet, deep enough to allow some impacts to make it all terminals with the exception of Livermore. The stratus is gradually mixing out this morning, with clear skies expected for all terminals away from the immediate coast (sorry Half Moon Bay) through the afternoon and early evening. There is very high confidence that the marine layer stratus will return overnight.

Vicinity of SFO...While we feel confident that the marine layer stratus will return overnight, the exact impact at SFO is less certain. As we saw this morning, microscale eddies and downsloping can create some clear patches at and around the terminal. If a cloud deck does move over SFO, expect high IFR or low MVFR ceiling heights.

SFO Bridge Approach...VFR with clouds confined north of the terminal.

Monterey Bay Terminals...The marine layer is a little more shallow at these terminals, which brought lower ceilings and and earlier clearing time than the Bay Area. While the afternoon should be clear, the stratus bank is hanging out just off the coast and there is a chance for encroachment over MRY at any time. A similar trend is expected tonight with IFR ceilings expected through mid Tuesday morning at both MRY and SNS.

MARINE

(Today through Saturday) Issued at 1129 AM PDT Mon Apr 6 2026

High pressure off the California coast will maintain light to moderate breezes across the coastal waters through the week. Locally fresh breezes will develop along the Big Sur coast this afternoon with the strongest wind near and south of Point Sur. Unsettled weather returns mid to late week, bringing light showers, a slight chance of thunderstorms, and moderate seas. Winds increase next weekend with a fresh breeze expected over the northern coastal waters.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 9 PM PDT Tuesday for Pt Pinos to Pt Piedras Blancas 0-10 nm.