Wildfire risk will remain substantial in much of California through at least this month, the National Interagency Fire Center said Nov. 1 in its monthly National Significant Wildfire Potential Outlook.
Risk will persist into December in some areas.
“The best scenario would be for rain or snow to move into the West from a series of strong early winter storms,” NIFC meteorologist Bryan Henry said in an interview. “Unfortunately, that does not appear likely over the next several weeks.”
But California soon could see less pressure from warm and fast-moving Santa Ana winds, which blow from high meteorological pressure to low over the Sierra Nevadas, accelerating and drying as they move downslope.
“The weather patterns that promote Santa Ana wind events need to change, and that is expected to occur beginning today,” Henry said Nov. 1.
Western fire activity this time of year is driven almost exclusively by wind events, he said. Recent Santa Ana wind speeds of 50 to 60 mph, with gusts nearing 75, have been common recently, “along with low humidities,” he said.
“We have seen humidity values as low as 1% across portions of Southern California for two days, which is extraordinary.” Usually, 3 to 4% humidities are considered low.
Earlier weather and fuel conditions also are in play.
Henry said precipitation over the last two to three months has been less than 25% of the long-term average across most of the Great Basin and California, and less than 5% in some areas.
Current dry conditions could cause trouble in early 2020.
“This is the last time, before it goes dormant, for vegetation to take up moisture in its root system, the effect being that when it exits dormancy in the spring, it’s already stressed from fall drought no matter what happens this winter,” Henry said. In 2020, “we could have some early issues with fire activity.”
Wildfires burning in California are consuming grasses and other fine fuels plumped by wetter-than-usual conditions from last winter into early summer, he said.
This year’s fuel crop “is providing for a more continuous fuel bed” that is not slowed or broken up by patches of barren ground or rock, Henry said. “Fires under the right weather conditions are able to burn more intensely. It kind of leaves the basis for what happened in the last couple of weeks.”
Boise-based NIFC on Nov. 1 said Southern California has above-normal significant large-fire potential, with acres burned for a given area exceeding the 10-year median, during November and early December at middle elevations and in areas prone to east winds. Other areas have normal potential.
Above-normal risk is predicted in Northern California in November, particularly the month’s first half, in the Sacramento Valley and foothills, western slopes of Sierra and Cascade mountain ranges, and part of the Mid Coast.
NIFC said sea-surface temperatures surrounding the Hawaiian Islands are warmer than normal — which should continue through February, leading to above-average temperatures in the region that includes Northern California.
California wildfires early Nov. 1 (Source: NIFC)
Kincade, 10 miles northeast of Geyersville, 77,758 acres, 65% contained.
South, 15 miles south of Platina, 5,332 acres, 76% contained.
Getty, one mile south of West Lake Village, 745 acres, 66% contained.
Burris, four miles south of Potter Valley, 703 acres, 94% contained.
Hill, three miles southeast of Ontario, 628 acres, 90% contained.
46th, Riverside area, 300 acres, 70% contained.
Caples, Eldorado National Forest, fully contained at 3,435 acres.