WIND EVENT ON TRACK. RED FLAG CONDITIONS BEGIN. POWER SHUTOFFS LIMITED.

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THE BIG PICTURE

The first major wind event of the fall season is ramping up Thursday afternoon, and will reach a peak from about 11PM Thursday through Friday morning. The strongest winds are expected overnight. There will be another ramp up in winds late Friday night, but these are not forecast to be as strong as the Thursday-Friday winds.

In the valley areas winds will generally gust to 35 mph at times, while in the hills gusts may exceed 65 mph or higher at the peaks of the North Bay.

Due to the continuing winds and much drier air and lower humidity that will arrive on Friday, a Red Flag Warning has been issued for the entire region.

THE WIND EVENT

As low pressure passes to our east, the winds will initially be gusty from the northwest. This will happen during the Thursday-early Friday period. This direction is not as dry as the winds that will come later.

As the low pressure center drops southeast, high pressure will begin to build in behind it. This will turn the winds to the north. This change will be underway through Friday morning.

So, even as the strong winds arrive late Thursday and early Friday, they will be changing direction, from northwest, to eventually northeast which will bring a dramatic drop in humidity which will dry out fuels.

Here is the forecast for 11PM Thursday.

During the day Friday the shift will be underway, to a much drier northeast direction.

Here’s the forecast for early Saturday.

Along with all of these winds turning drier, relative humidity will take a plunge from Friday through Saturday, with values from the single digits to teens by Saturday afternoon. This will be a major factor in drying out fuels, and increasing fire risk.

RED FLAG WARNINGS AND POWER SHUTOFFS

PG&E has announced that only around 700 customers in each of Sonoma and Napa counties will have power shutoff Thursday through Saturday. These customers are mostly in rural and mountainous areas. Even fewer homes will be impacted in other North Bay counties like Mendocino and Lake. Head to this link to find out if you or someone you know will be affected: https://pgealerts.alerts.pge.com/outage-tools/outage-map/

Although the strongest winds are expected from 11PM Thursday through early Friday morning, the combination of drying fuels, lower humidities and continuing gusty winds has prompted the NWS to extend Red Flag Warnings through Saturday.

Another significant uptick in winds is expected late Friday into early Saturday.

The main takeaway is to cancel or delay until after Saturday any outdoor activities that may cause a spark, including the use of power tools, mowers and the like.

We will have additional updates as conditions warrant.