Santa Ana winds to bring post-Thanksgiving fire risk
A motorist was treated to an ominous view of the Mountain View Fire while driving on Highway 338 near the Nevada border in Walker, California, on Nov. 17. He described it as "driving into Armageddon."
As Thanksgiving comes to an end in Southern California, the ingredients for a common and troublesome fall occurrence will be coming together across the region.
As high pressure builds across the interior West, a Santa Ana event is expected to unfold across the region to end the holiday week, bringing an increased wildfire threat, as well the potential for some localized damaging winds.
"A storm system will move through the Northwest and Rockies Wednesday into Thursday. Behind this, strong high pressure will move into the West and slide across the Great Basin," explained AccuWeather Senior Meteorologist Dave Samuhel.
As this high pressure moves inland, strong northeasterly winds will develop in Southern California on Thanksgiving day and can persist into Saturday in some locations.
Samuhel explained that this is a common set up to get Santa Ana winds in the autumn months in Southern California.
"The position of the high pressure creates northeasterly winds across Southern California, which blow from the dry upper deserts, through the Transverse Ranges and then off the coast."
The air with these winds descends from high to lower elevation, which also causes it to accelerate and become even drier.
"The extremely low relative humidity associated with these winds leads to high fire threat," Samuhel said. "The gusty winds can then allow fires to spread very rapidly."
Along with the high fire threat, the wind gusts can also be locally strong enough to cause some damage to trees and power lines, especially in canyons and passes where the wind gets funneled on its way to the coast.
High-profile vehicles will have to be alert for dangerous crosswinds that can threaten to cause blowovers.
Santa Ana winds often lead to intense heat in Southern California as well; however, Samuhel says this will not be the case this time.
"The high pressure moving into the West this time will be associated with a blast of chilly air. This will lead to what is called a 'cool Santa Ana,' in contrast to other Santa Ana events where temperatures can soar toward the triple digits," Samuhel explained.
However, temperatures will still trend noticeably higher. Temperatures in downtown Los Angeles are expected to climb from the middle to upper 60s F on Thanksgiving into the lower to middle 70s for Friday and Saturday.
Forecasters warn that just because temperatures are not forecast to reach high levels, it doesn't mean that the fire risk won't be high.
"Heat can cause things to be drier or dry out faster, but it's not the only driver of fire risk. If vegetation is very dry and humidity is very low, fires can still start very easily and spread very quickly in gusty winds," Samuhel added.
Residents are urged to be prepared and heed guidance from local officials. Those planning to do any Thanksgiving cooking outdoors, should be sure to properly contain and extinguish any flames or heat sources.
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