SAN DIEGO -- Gusty Santa Ana winds and low humidity in the forecast this week prompted the National Weather Service to issue a red flag warning for San Diego County Monday, signifying a high risk of wildfire.
A high wind warning also went into effect Monday, with both warnings set to expire late Thursday night, according to the NWS. But the Santa Ana winds could persist into Friday or Saturday, which would likely mean an extension of both warnings.
The San Diego Fire-Rescue Department and San Diego Gas & Electric are both beefing up staffing levels this week to deal with the rare late-season fire danger.
"Meteorologists at the National Weather Service have not seen models for a Santa Ana event like this in many years," SDFD Chief Brian Fennessy said. "We are being vigilant in up-staffing to protect San Diegans and their property. We ask that residents practice their evacuation plans and be prepared in case of a wildfire."
SDFD will increase staff through Thursday by adding two strike teams of 10 brush rigs, one strike team of five fire engines, two water tenders and two helicopters, spokeswoman Monica Munoz said. Dispatcher staffing will also be increased.
SDG&E officials said they would call customers in wind-prone areas Monday "to alert them of the possibility of power outages related to high winds and reminding them to be prepared to activate their personal emergency plan."
Like the fire department, the county's energy utility will also increase staffing throughout the week.
"As a precaution, we will be staging SDG&E field crews and contract firefighters in the areas where the winds are expected to be the strongest," spokeswoman Colleen Windsor said. "Proactively locating crews in those areas will shorten response time if there is an outage."
SDG&E -- which last week lost a ruling in relation to the 2007 wildfires the company was found responsible for starting -- said it may need to turn off power in certain areas "if weather conditions threaten the integrity of our system and create the possibility of an imminent emergency."
Fire officials said several years of drought coupled with heavy rains last winter created significant fire fuel in the form of underbrush and grass. But the lack of recent rainfall and low humidity levels have dried out the extra fuel, making it ready to spark.
The dry fuels combined with the Santa Ana winds and low humidity levels are why the fire danger is so high this week despite the forecast calling for mild temperatures in the 50s, 60s and 70s. Humidity levels will be in the 10 to 15 percent range Monday and the 7 to 15 percent range from Tuesday through Saturday.
The strongest and most widespread winds are expected for late Monday evening into Tuesday and again for late Wednesday night into Thursday. In most areas, winds are expected to be 20 to 30 mph with gusts to 55 mph, though stronger sustained winds are possible in higher elevations and wind-prone areas. Isolated gusts up to 70 to 80 mph are possible on Tuesday and Thursday.
The U.S. Forest Service's Santa Ana Wildfire Threat Index, which categorizes Santa Ana winds based on anticipated fire potential as extreme, high, moderate, marginal or no rating, predicts that Thursday has the potential to be the most dangerous day this week for Santa Ana-driven wildfires.
With a high threat level Thursday, the Forest Service warns that "upon ignition, fires will grow very rapidly, will burn intensely, and will be very difficult to control." Marginal danger is predicted for Monday and Wednesday and moderate danger for Tuesday, Friday and Saturday.
SDFD officials and the NWS warned residents to "avoid activities that could spark a fire" and warned of the dangers of high winds that include power outages and damaged or toppled trees or power lines.