Wildfire risk to ramp up for Southern California as Santa Ana threat looms

Mary Gilbert

Southern California has enjoyed a break from wildfire concerns in recent weeks, but a midweek change in the overall weather pattern will put some residents on high alert.

The most recent significant wildfires to burn in the region were the Apple and El Dorado fires earlier in November. These two fires burned a combined 56,168 acres before they were declared 100% contained on Nov. 16 by San Bernardino National Forest officials.

A new wind threat and subsequent fire threat will ramp up this week.

"An area of high pressure is expected to build from the northern Rockies to the Great Basin this week, promoting a strong northeasterly offshore flow over Southern California," AccuWeather Meteorologist Adam Sadvary said.

As these northeasterly winds strengthen into midweek, they will work to elevate the threat for fire weather conditions across Southern California. Winds will slowly strengthen throughout the start of the week, but will reach a concerning threshold by Tuesday. On Tuesday, winds will become moderately gusty, mainly across the mountains and valleys of Santa Barbara, Ventura and Los Angeles counties.

Wind gusts of 25-35 mph will be possible across these regions, especially later Tuesday into Wednesday, leading to an elevated fire threat.

However, by Wednesday a much more significant event is forecast to develop -- Santa Ana winds.

Santa Ana winds are high-speed and dangerous northeasterly winds that blow from the mountains to the coast in Southern California as areas of strong high pressure build across the interior West.

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High pressure over the interior West will likely be at peak strength from late Wednesday through much of Thursday, which will kick off a moderate to strong Santa Ana wind event for Southern California.

"Wind gusts of up to 50-60 mph with an AccuWeather Local StormMax™ of 75 mph will be possible at some of the highest elevations of the southern Sierras and San Bernardino Mountains," Sadvary said.

High winds, dry weather and low humidity levels are three of the main ingredients necessary to increase the level of fire risk.

"This Santa Ana wind event will pose a high fire threat along the Southern California mountain ranges. The combination of strong wind gusts and dangerously dry relative humidity levels (as low as 5-15%) can cause any rogue spark to spread rapidly into a turbulent wildfire," Sadvary explained.

To make matters worse, Southern California will remain very dry leading up to this Santa Ana wind event. Much of the region has not recorded any measurable rain since early November. The last time locations like Santa Barbara and Palm Springs, California, recorded measurable rain was back on Nov. 8. In November, these two locations received a dismal 3 percent and 8 percent, respectively, of their average monthly rainfall.

Any fire that starts during this Santa Ana event can quickly grow out of control. Very dry fuels including grass and trees will be readily available for a wildfire to consume. In addition, strong winds will allow wildfires to rapidly rack up burned acreage.

In addition to assisting with rapid fire growth, strong winds can lead to some property damage and can also bring down trees and power lines. Planned rolling electricity blackouts may be possible, as crews work to limit possible ignition points.

Strong winds can also lead to hazardous driving conditions as dangerous crosswinds are expected to develop, especially for elevated passes. These dangerous crosswinds will be especially troublesome for high-profile vehicles that are easily susceptible to roll-overs.

If any fires manage to ignite this week, they will contribute to what has already been an historic fire season for the state of California. Unfortunately, the 2020 fire season has been one for the record books.

In California, half of the top 10 largest wildfires to ever scorch the state occurred in 2020, according to CAL FIRE. 2020 had the first, third, fourth, fifth and sixth-largest wildfires in state history. The single largest wildfire in the history of California occurred this summer when the August Complex fire reached an astounding 1,032,649 acres. The August Complex fire burned nearly 1,000 structures and led to at least one death. Year-to-date, fires have burned nearly a combined 4.2 million acres across the state of California.

While the strongest winds from this Santa Ana event will begin to ease on Friday, winds may remain gusty enough to keep fire weather conditions elevated for some into the weekend.

Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.