Weather ingredients in place for rapid wildfire development across western US
Firefighters said they stopped forward progress of this fire burning near Interstate 80 in Rodeo, California. Aerial video shows the fire close to a tank farm.
Stiff breezes will substantially elevate the risk of new wildfire ignition and could cause existing fires to rapidly spread through the middle of this week in the western United States.
Although the winds are not forecast to be as strong as several weeks ago, they will be potent enough to trigger significant wildfire growth.
"There is a high to extreme risk of rapidly spreading fires from southern Nevada and northern Arizona to Wyoming," AccuWeather Senior Meteorologist Brett Anderson said.
Ongoing heat and worsening dry and drought conditions in much of the region have begun to significantly dry out the spring growth.
The dry brush and other vegetation now become fuels for fires.
In the absence of high humidity and widespread drenching thunderstorm activity that the North American monsoon would typically bring around this time of the summer, conditions are ripe for new wildfires to get going.
The Crews Fire burns near Gilroy, Calif., Sunday, July 5, 2020. (AP Photo/Noah Berger)
The North American monsoon is a change in the overall wind direction that brings up tropical moisture from Mexico by way of the Gulf of Mexico or the eastern Pacific Ocean.
Higher humidity levels in turn allow thunderstorms to erupt during the afternoon hours, which can bring pockets of heavy rain and flash flooding.
Thus far, moisture has been very limited as only a small number of storms have tended to pop up. And those that have developed have brought very little rain.
The ongoing risk from the storms is for lightning strikes to spark new fires.
A storm system tracking through the Northwest will cause winds to increase across the outlined region, according to Anderson.
"This increase in wind coupled with relative humidity levels of 5-15 percent and ongoing moderate to severe drought conditions is a recipe for small grass fires to quickly turn into a raging inferno that can move very quickly," Anderson explained.
In the case through the middle of this week, it is gusty winds from the west and southwest that can average 15-25 mph with higher gusts that can fan the flames of any existing fire or sparks from a natural or man-made source.
People are urged to be extremely cautious with outdoor flames, particularly when working with campfires, grills and power equipment. Never park vehicles over dry brush as the exhaust system from a vehicle that has been running is hot enough to catch the brush on fire.
A livestock trailer drives along Canada Road as the Crews Fire burns near Gilroy, Calif., on Sunday, July 5, 2020. (AP Photo/Noah Berger)
Always extinguish cigarettes in a proper container and never throw burning material outside of your vehicle.
Those that are towing vehicles should constantly monitor the trailer to make sure the tires have not gone flat and/or the brakes have not overheated. Either scenario can produce sparks, which can set brush along the side of a road or trail on fire.
Be sure to check local and county regulations and bulletins as the use of open flames and fireworks may be banned under the conditions this summer.
"After Wednesday, there will be a slight reduction in the wind, but not enough to substantially lower the fire risk in this region," Anderson said.
"Due to the weather conditions, smoke from large fires may linger close to the ground in some areas, leading to locally poor air quality," Anderson added.
Temperatures are forecast to climb even higher this weekend to next week over much of the interior western U.S. with potentially the hottest weather of the summer and perhaps in recent years.
While the pattern may yield an uptick in thunderstorm activity over the mountains next week, there will be a lightning strike risk and most of the storms won't carry drenching rain.
Even though the number of acres burned thus far in 2020 is well behind the 10-year average of about 2.5 million, the 1.5 million acres burned as of July 7 is ahead of 2019's pace by a couple hundred thousand acres.
As the summer progresses and the risk of a sub-average monsoon increases, the more likely it becomes that the number of acres burnt continues to trend toward average.
There are already a number of large and destructive fires burning across the Southwest.
As of Tuesday night, the Bighorn Fire in Arizona was about 75% contained but had consumed nearly 120,000 acres and is the largest single fire of the year so far.
Meanwhile, the Bringham Fire, also in Arizona, began on June 4 from a lightning strike and is only about 40% contained with 23,100 acres burned so far.
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