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Sunny and breezy today
A sunny, breezy day is underway with temperatures ranging from low 60s at the coast to low 70s inland. San Francisco sunset, 5:08 PM.
Last Friday’s system had a winter flavor with steady downpours in parts of the Bay Area and a fresh blanket of Sierra snow. We might not be on a straight track toward winter just yet.
A couple of wind events will dry out Northern California and increase the fire danger.
Parts of the Bay Area had a couple of good soakings last week. Why is fire danger still a concern?
Last Friday’s storm was an overachiever and produced over an inch of rain in parts of the North Bay. Some South Bay neighborhoods did not receive measurable rainfall.
While the increased moisture is helpful, the upcoming pattern will dry out the "fuels" over the coming week.
Until the Bay Area receives significant rain, our fire season continues.
Have there been major fires in the month of November?
Strong winds caused the Camp Fire, in Butte County, to explode in size on November 8, 2018. The fire front traveled rapidly at the rate of 80 football fields per minute.
This fire has the somber distinction of being the deadliest fire in California history. The Camp Fire burned 153,000 acres and killed 85 people.
What is the weather pattern that produces these strong winds?
When forecasting, during the fall, this is the upper level weather pattern meteorologists are looking out for -
First – A storm develops to our north. Instead of moving into Northern California, it takes an inside track to the east.
Second - an upper level high-pressure system forms in the Pacific.
The pressure difference between these two systems produces a wind from the north. When these systems intensify, strong winds blow over land and usher in dry air.
The moist, onshore flow that we are accustomed to is suspended. The combination of the dry air, gusty winds, and low moisture levels in the vegetation always make fall wildfires a threat. We are still at the peak of fire season.
The strength and proximity of the different pressure systems dictates the strength of wind events.
What should we look out for this week?
There are two main wind events we are tracking.
Sunday: The first wind event develops. Fire danger will be elevated. Northerly winds will be increasing. Gusts could range between 30 – 45 mph. The recent rainfall was beneficial and should not lead to extreme fire danger.
Wednesday: The second wind event begins (possibly as early as Tuesday night). While there is still some uncertainty about the forecast details, this event could be stronger.
Gusts could possibly range between 40 – 65 mph.
Since fuels have had a chance to dry out, the conditions may lead to a more critical situation. Red Flag Warnings could possibly be issued for parts of the Bay Area.