Storm to bring spotty rain, wind and lightning to fire zone in western US

As temperatures once again trend upward with a building heat dome in the western United States, a plume of moisture may bring fire-quenching rain to parts of the region and boost the fire risk to others.

As heat builds, fires rage and spotty thunderstorms associated with the North American monsoon continue in the western United States, AccuWeather meteorologists are tracking a storm system that may help ease the tinder-dry conditions in some areas but increase dangers in others into this weekend.

A surge of moisture with origins from Mexico and the tropical Pacific will stream northward across California and Nevada into Saturday.

"Along with raising humidity levels in California and part of Nevada, it will lead to an uptick in showers and thunderstorms," AccuWeather Senior Meteorologist Heather Zehr said.

"While the setup will bring the usual risk of lightning strikes, which could start new fires and gusty winds that could fan the flames of existing fires, it may bring more rainfall to more areas than what typically occurs during the monsoon," Zehr explained, "The combination of higher humidity levels and rainfall can help to ease the fire threat in some cases."

On Friday, a batch of clouds and showers was seen spreading across portions of California and Nevada from NOAA's GOES-WEST weather satellite. The clouds spanned from the Grand Canyon, over Las Vegas and into central California.

Most of the rainfall may be confined to the Sierra Nevada and its foothills. As it advances into the Northwest later this weekend and finally across the northern Rockies by early next week, it may have little moisture left.

Away from the clouds, showers and thunderstorms, the heat dome will build and strengthen in the West. Temperatures will trend upward, following a slight downward slide from last weekend to the start of the week.

For example, most days through Monday will challenge daily record highs in Boise, Idaho. Highs will routinely top 100 F. Temperatures on at least one day may come within a few degrees of the all-time record high of 111 set in July of 1898 and 1960.

Temperatures will climb to near 110 in Las Vegas from Saturday to at least Tuesday, which will be 5 degrees above the historical average. Highs most days during the same period in Salt Lake City will range from 100 to 105, which is 5-10 degrees above the historical average and some daily record highs may be challenged.

The heat is forecast to continue over much of the West next week.

"In the Northwest, this feature may cause more problems than benefits, as more of the thunderstorms that occur will tend to have little or no rain but pack the gusty winds and lightning strikes that are problems for wildfires and firefighting efforts," AccuWeather Meteorologist Brandon Buckingham said.

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At least 95 large active wildfires were being managed with full suppression strategies nationwide as of the start of August, according to the National Interagency Fire Center. Nationwide, current fires have burned 2,180,105 acres. So far this year, 28,154 wildfires have burned 4,449,282 acres. People have caused more than 25,000 wildfires that have burned nearly 3 million acres. Lightning ignited about 2,740 wildfires and burned 1.1 million acres.

The majority of the wildfires this season in the U.S. have been west of the Mississippi River.

The Park Fire in California spread rapidly and has burned nearly 400,000 acres alone, according to the NIFC. Active fires in Oregon have burned nearly 1 million acres.

The existing fires are spewing out huge amounts of smoke over the western U.S. Much of this smoke has been and will continue to be trapped by the heat dome. At times, the smoke will reach down to ground level, exposing many individuals to major health hazards.

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