By AccuWeather Meteorologist
Updated Jul. 18, 2021 6:26 AM MDT
After flooding rain in the Southwest from monsoon moisture, storms are headed for the Northwest through the early week, bringing dangerous lightning risks that can spark wildfires.
Wind gusts will begin to increase across Washington and Oregon on Sunday as a monsoon-powered storm approaches British Columbia.
"Monsoon moisture will get drawn northward across areas east of the Cascades in Washington and Oregon, as well as into Idaho and northwest Montana into the early part of the week," said AccuWeather Meteorologist Renee Duff.
While this may sound like good news to help fight the numerous active wildfires, calm record-challenging heat and disperse smoky air, AccuWeather forecasters predict it can have negative consequences.
"There is concern that the uptick in shower and thunderstorm activity may actually cause more harm than good," said Duff.
Not as much moisture is expected to make it into the Northwest as what transpired in the Southwest, where flash flooding occurred in places like Phoenix. The position of the high pressure can also limit any rainfall across much of the area.
Any small changes in the high pressure location will make the difference with how far west or east monsoonal moisture is able to move during the period, according to AccuWeather Meteorologist Tyler Roys.
With wildfires already raging in the West, including the Bootleg Fire in Oregon, thunderstorms are forecast to have the potential to spark more fires in areas that have not had any rainfall.
"These storms can cause cloud-to-ground lightning and ignite fires," said AccuWeather Meteorologist Thomas Geiger.
The combination of dry fuels, low relative humidity and breezy conditions will greatly increase the risk for dry lightning.
"Dry lightning occurs when a thunderstorm produces little-to-no rainfall, due to how dry the air is near the surface, which causes any precipitation to evaporate," said Duff.
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Lightning strikes were responsible for 71% of areas burned in the United States from 1992-2015, according to the United States Forest Service.
There have already been at least 34,596 wildfires across the United States so far in 2021, burning over 2 million acres. This is well above last year's 28,423 fires by July 16, 2020.
"Dry lightning is notorious for sparking new blazes, especially when the ground is as dry as it is currently across the Northwest," said Duff.
Over 60 percent of the West is in extreme drought, according to the United States Drought Monitor. Oregon's 55 percent extreme drought and 89 percent severe drought really emphasize how dry the ground is there. So far during the month of July, neither Pendleton nor Medford, Oregon, has received any rainfall.
Cities within the area to be impacted include Reno, Nevada; Twin Falls and Boise, Idaho; and Bozeman, Missoula and Helena, Montana. Several popular outdoor activity and tourist locations are under risk as well, including Yellowstone National Park and Boise National Forest.
"The lightning will also pose a risk to those outdoors," said Duff.
Anyone camping or otherwise participating in outdoor activities should remain aware of the forecast and keep an emergency supply kit in their car or on their person, in case of evacuations. Forecasters want to emphasize that the common misconception that lightning can only occur when it rains is false. Lightning can occur without any precipitation involved, and can even strike outside its origin thunderstorm.
Those enjoying campfires or grilling should make sure to extinguish any fires when they're finished or unattended, and officials ask that residents and visitors heed all fire restrictions. Stage 1 Fire Restrictions are in effect in Glacier National Park.
By way of a slight silver lining, though, the monsoon can bring a small amount of heat relief to areas of the West that will have been suffering under extreme and challenging heat.
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An area of low pressure will shift south from the Gulf of Alaska along the west coast of Canada, according to Roys. This can also help with lowering temperatures, especially along the coast.
Unfortunately, many areas will remain at above-average temperatures.
Billings, Montana, is anticipated to peak at 104 degrees Fahrenheit on Monday, just one degree shy of tying its July 19 record from 1960 just ahead of the moisture surge.
After that, temperatures will fall into the 90s, gradually decreasing throughout the week. While still above average, these temperatures can feel like quite the relief after triple digits, especially at night when temperatures can drop back into the 60s throughout the week.
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