UPDATE
Issued at 932 PM PDT Wed Sep 11 2024

Winds at sea level and lower elevations are for the most part continuing to ease through the evening, the exceptions are in the gaps, a few areas on hill tops and mountain tops where onshore winds are still gusty at this hour. The SFO-SAC pressure gradient still predominates but is more moderate since decreasing to 3.4 mb at 9 pm.
Gale warnings over the southern SF Bay and southern inner coastal waters were lowered to small craft advisories for tonight and Thursday morning.

SHORT TERM
(This evening through Thursday)
Issued at 137 PM PDT Wed Sep 11 2024

A cold front currently draped off the West Coast will plunge into Northern California this afternoon bringing mild and windy conditions. Widespread wind gusts of 30 mph are expected this afternoon and evening with wind gusts of 45+ mph expected through gaps, passes, and other favorable locations like SFO and the Salinas Valley. While the overall fire threat is on a downward trend due to lower temperatures and higher relative humidities, fuels still remain critically dry with large fires still possible.
Therefore, any fire that starts will have no problem spreading and strong winds will only exacerbate that. Winds will decrease tonight as the upper-level trough axis swings out and low- amplitude upper-level ridging builds in. In addition, winds in Napa and Sonoma Counties will become northerly/offshore during the overnight and morning hours until the sea breeze prevails in the afternoon.

LONG TERM
(Thursday night through next Tuesday)
Issued at 137 PM PDT Wed Sep 11 2024

Friday will be the warmest day of the week as a weak, low- amplitude upper-level ridge builds into place, acting as a break in between troughs more than anything. Northerly/offshore flow will continue during the overnight and morning periods through Saturday morning in Napa and Sonoma Counties. Upper-level troughing will start to take shape off the West Coast Saturday promoting cooler conditions and onshore flow. Confidence is increasing in an upper-level low and associated cold front sweeping across the region Sunday bringing below normal temperatures and renewed chances for measurable rainfall. This unsettled pattern will persist into next week as an upper-level trough develops on the heels of the upper-level low.

AVIATION
(00Z TAFS)
Issued at 949 PM PDT Wed Sep 11 2024

Stratus clouds and patchy fog /IFR-MVFR/ are steadily developing along the coast and in the nearby coastal valleys, otherwise it's VFR. Onshore winds are continuing to ease this evening, and expect less gusty onshore winds Thursday. Coastal clouds and fog IFR-MVFR continuing tonight and Thursday morning spreading locally inland with IFR-MVFR also developing under nocturnal radiative cooling.

Vicinity of SFO...IFR ceiling tonight and Thursday morning due to a stratus intrusion. Stratus (and patchy fog) development has increased on the coastal side of the SF Peninsula much like the HRRR output shows. Low to very low confidence if there will be partial clearing early Thursday morning, which may occur due to another weak and dry cool frontal boundary arriving early Thursday morning. Gusty west wind to 20 to 25 knots developing Thursday afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...IFR ceilings tonight and Thursday morning, then late morning improvement to MVFR-VFR. West to northwest winds 5 to 10 knots tonight and Thursday morning, west to northwest winds 10 to 15 knots Thursday afternoon and early evening.

MARINE
(Tonight through next Tuesday)
Issued at 922 PM PDT Wed Sep 11 2024

Winds gradually decreasing overnight, but remaining breezy. Winds increase Thursday afternoon with Gale force gusts in the outer waters.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory until 3 AM PDT Thursday for Mry Bay-SF Bay N of Bay Bridge.

Small Craft Advisory until 3 AM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory until 3 PM PDT Thursday for Pigeon Pt to Pt Pinos 0-10 nm.

Small Craft Advisory until 9 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.

Gale Warning from 9 AM Thursday to 3 AM PDT Friday for Pt Arena to Pt Reyes 10-60 NM.