textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 218 PM PDT Tue Sep 8 2026

- Warming and drying trend will bring widespread moderate to major HeatRisk through Thursday

- Cooler temperatures, closer to normal, Friday into the weekend

SHORT TERM

Issued at 1207 AM PDT Wed Sep 9 2026 (Today through Thursday)

A northward intrusion of mainly mid and high level tropical moisture from the remnants of Marie continues to move in across the forecast area. The Tuesday evening 5 pm (00z) Vandenberg upper air sounding showed a cloud layer as low as 16,000 feet. Cirrus at ~ 30,000 feet with the subtropical jet stream was evident on the Oakland upper air sounding. Under the mid and high level clouds, it's currently much drier to the ground with a sliver of coastal dew point temps in the 50s to around 60F to Santa Cruz, otherwise it is drier away from the coastline. Warm temperatures will continue tonight with the incoming cloud layers greatly reducing radiative cooling. Sub-cloud layer dry air does at times tend to stay land-locked over the highly varied terrain of CA, until diurnal mixing, diffusion, wind transport and/or precipitation get going to thoroughly mix in the higher humidity to ground level.

KVBX Vandenberg radar does show high based light showers recently. GOES West lightning mapper shows spotty lightning activity to the southwest as well and this lightning is close to the leading edge of a mid-upper level moisture gradient. There's a history of rain and lightning activity from earlier today well to our south, a signature of favorable thermodynamics and jet stream dynamics west of strong 500 mb ridging even at 590+ heights. This bears close monitoring in the nearest term.

No changes to the forecast at this time. A Heat Advisory remains in effect for the entire forecast area until 10 PM Thursday. Strong high pressure will result in warm morning low temperatures and daytime highs in the 90s to lower 100s over much of the forecast area. Along the immediate coastline an afternoon sea breeze may help nudge temperatures back down. This is a complex pattern, please stay tuned to the latest updates.

From the earlier forecast discussion:

Please remember these tips to help mitigate impacts from heat exposure:

-Suspend unnecessary outdoor activities during the extreme heat, but if you must be outdoors, take frequent breaks in the shade or AC and drink cool water. -Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke! Heat Stroke can be deadly if not treated immediately by a medical professional. Call 911 if you suspect someone is suffering from Heat Stroke. -Wear a life jacket, swim near a lifeguard, and check conditions before entering the water if going to a river or ocean to cool off. Rivers and the ocean are extremely cold, and Cold Water Shock can turn into paralysis and drowning if you are not careful. -Use a cool and damp towel on your body if you do not have AC and are feeling hot. Or, take a cool shower or bath. -Do not leave kids or pets in a parked car. -Ensure pets and livestock have access to shade and water.

LONG TERM

Issued at 1207 AM PDT Wed Sep 9 2026 (Friday through next Tuesday)

The main concern is the short term.

A late week and weekend cooling trend remains in the forecast. The strong ridge over our forecast area will weaken. Dry weather is forecast.

AVIATION

(12Z TAFS) Issued at 303 AM PDT Wed Sep 9 2026

VFR conditions are expected to continue under a blanket of high clouds. Light offshore flow will continue to disrupt the marine layer today, and high clouds are suppressing radiative cooling this morning. These factors are both contributing to the high confidence VFR forecast across the terminals today. An afternoon sea breeze will easily overpower the offshore gradient, with a moderate to fresh breeze expected in the afternoon and evening. More consistent onshore flow is expected to return by Thursday, bringing low clouds back into play.

Vicinity of SFO...High confidence in VFR conditions through the TAF period. Winds are currently light and variable but the NW sea breeze will take hold this afternoon. Winds reached 18KT Tuesday and will be similar this evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...While it's hard to tell exactly what's happening under the high clouds, high resolution models are indicating a 10% chance for ceilings at both MRY and SNS by 18Z this morning. The much more likely scenario is for VFR conditions to persist through the TAF period under high clouds for much of the day. Light drainage winds in the morning will flip to a moderate onshore breeze in the afternoon.

MARINE

(Today through Monday) Issued at 303 AM PDT Wed Sep 9 2026

A moderate NW breeze and moderate seas will continue through Thursday. By Friday, a tighter pressure gradient will cause a steady increase in wind speed through the weekend, with a strong NW breeze expected Saturday and Sunday. A moderate SW swell from distant tropical cyclones will continue through the week.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 1 AM PDT Thursday for CAZ006-506- 508-529-530.

Heat Advisory until 10 PM PDT Thursday for CAZ006-502>506- 508>510-512>518-528>530.

PZ...Small Craft Advisory from 3 PM Thursday to 3 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM- Pt Pinos to Pt Piedras Blancas 0-10 nm.