Heat to build, elevate fire danger in southwestern US this week

By Renee Duff, AccuWeather meteorologist
July 23, 2018, 10:18:40 PM EDT

Near-record heat will set the stage for a heightened risk of wildfires in the southwestern United States, including Southern California, this week.

While the Southwest is no stranger to intense heat in the summer months, the upcoming pattern is likely to put several decades-old high temperature records to the test.

The area of high pressure that has brought record-breaking temperatures to the South Central states will build westward into the middle of the week, according to AccuWeather Senior Meteorologist Ken Clark.

This will shift the core of hot air into the deserts and even coastal communities of the Southwest.

High temperatures can exceed 10 degrees Fahrenheit above normal in Phoenix and Las Vegas, where average daytime temperatures are already in the 100s F.

Static SW Heat This Week

The pattern over the next several days is likely to produce the hottest weather of the year so far in the deserts.

“In Southern California, temperatures soaring well into the triple digits seems likely for at least the valleys and into the 90s F for coastal cities,” Clark said.

Daily record highs will be challenged for one or more days next week in Los Angeles, Burbank and Palm Springs, California; Las Vegas; and Phoenix.

"Temperatures at the beaches are expected to stop short of reaching the sizzling highs endured earlier this month," AccuWeather Senior Meteorologist Kristina Pydynowski said. "However, it will still turn warmer with highs in the 80s and some records being challenged. This includes in San Diego, where a high in the middle 70s is more common this time of year."

People will need to take precautions in the blazing conditions, including limiting outdoor exercise to the morning or evening hours, drinking plenty of water, wearing light-colored and loose-fitted clothing and taking frequent breaks in the shade while working outdoors.

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Visitors to the region who may not be accustomed to such intense heat should be especially cautious.

The excessive heat can increase the risk of tire failure when traveling at high speed on area roadways for long periods of time. Airline weight restrictions and delays are possible, while some flights may be canceled.

Outside of localized breezes, air tends to move very little under large areas of high pressure, which results in air stagnation. This will lead to poor air quality concerns next week, especially around and downwind of wildfires.

People in sensitive groups, such as the elderly, children or those with respiratory problems, should limit time outdoors in this pattern.

“Unfortunately, the heat will mean continued problems with wildfires,” said AccuWeather Senior Meteorologist Jack Boston.

A phenomenon known as sundowner winds may greatly increase the wildfire threat in part of Southern California through midweek.

Static Sundowner 3 pm

"The windiest time of these days around the Santa Barbara will be in the afternoon and overnight hours and can cause temperatures to spike at unusual times of the day," according to Pydynowski.

"A similar set up fanned the destructive Holiday Fire earlier this month and caused temperatures to soar to a record high of 102 F in Santa Barbara at night," she said.

The growing Ferguson Fire burning near California’s Yosemite National Park has claimed the life of one firefighter.

More than two dozen other large wildfires are charring land across the Southwestern states, according to the National Interagency Fire Center.

The fires are being fueled by a drought that has only grown more severe and widespread since the beginning of the year.

CA Fire AP

A fire transport drives along Highway 140, one of the entrances to Yosemite National Park, on Monday, July 16, 2018, in Mariposa, Calif. (AP Photo/Noah Berger)

With building heat and mainly dry weather expected for much of the week, the risk of additional wildfire ignition will be high.

While afternoon thunderstorms will ignite over the highest terrain of the Southwest, coverage will not be widespread and rainfall not nearly enough to completely wipe out the drought or douse ongoing wildfires.

Instead, lightning strikes accompanied by little to no rainfall may spark new blazes and gusty winds stirred by the storms can cause erratic wildfire behavior.

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