Wildfire smoke, uptick in heat to accompany western US monsoon activity

The location of the ridge across the West and Central states will play a major role in the pattern, impacting monsoonal activity, temperatures and even transportation of wildfire smoke.

Across the interior West, spotty afternoon thunderstorms have become a part of the normal pattern over the last few weeks. While locally drenching thunderstorms have resulted in areas of flash flooding for portions of the interior Southwest, locations closer to the coast have missed out on much of the activity.

The position of a ridge of high pressure over portions of the interior southwest and south-central U.S. has aided in the transportation of Pacific moisture into the Four Corners. Daily chances for afternoon thunderstorms have become a theme in the Southwest under a consistent regime of prevailing southerly and southeasterly winds.

"The annual flip of the wind from the west to the south or southeast, known as the North American monsoon, brings in enough moisture from the tropics to raise humidity levels, which helps trigger thunderstorms over much of the western U.S. in the summer," explained AccuWeather Senior Meteorologist Alex Sosnowski.

Due to the ridge's position through midweek, forecasters are highlighting a general decline in monsoon intensity across northern Utah, Nevada and Wyoming. However, locations around the Four Corners are projected to observe near-average monsoon activity through this week.

"As high pressure expands into the Northwest, this could allow for a rebound of monsoon activity across the Four Corners and could direct some moisture into California by next weekend. Across the mountainous terrain of Southern California and the Sierra Nevada, weekend plans could be impacted," explained AccuWeather Meteorologist Joseph Bauer.

Core of heat migrates

Not only has this pattern over the Southwest ushered in pockets of moisture to the region, but it has also promoted an uptick in summertime heat. As the ridge builds more over the Central states early this week, the core of the heat will shift into the Plains.

This week, daytime highs are projected to soar into the 100s F across areas of northwest Texas, eastern Colorado, Oklahoma, Kansas, Nevada and even South Dakota at times. AccuWeather RealFeel® Temperatures will rise even higher from early to midweek, surpassing 110 degrees Fahrenheit in some locations across the Plains.

Temperatures along the West Coast will continue to trend slightly below historical averages early this week, with cities like San Francisco not expected to have daytime temperatures surpass the 70-degree mark through Monday.

By midweek, however, AccuWeather meteorologists say that high pressure will begin to build back across the central West and lead to a noticeable uptick in temperatures for most areas through the upcoming weekend.

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"By next weekend, many valley locations across the interior West could surge into the triple digits and could challenge daily record high temperatures. The heat could be particularly impactful in the Northwest, especially for those without air conditioning," noted Bauer.

Wildfire smoke expands

As of July 28, 103 large active wildfires were burning in the United States, according to the National Interagency Fire Center (NIFC), with a notable amount of these wildfires likely ignited by lightning strikes. Most active large fires are located across the Western states, including Oregon, Washington, Idaho, California, Nevada, Arizona, Utah, New Mexico and Wyoming.

One notable fire producing a prevalent plume of smoke is the Park Fire near Chico, California. Area evacuations, as well as road and trail closures, have been in effect over the last several days due to the extreme wildfire behavior exhibited, its location and its rapid growth.

"Smoke and air quality issues are expected to continue across the northern and central Intermountain West this week as high pressure returns back over the region," noted Bauer.

Air quality alerts have been issued across portions of the Northwest, warning residents of unhealthy levels of particulate matter or smoke present in the air into at least early this week.

Bauer added that while the Pacific Northwest and portions of the northern Intermountain West will see some rain through Tuesday this week, after that it looks to turn dry with a significant warmup into the weekend. With the potential for a stretch of dry weather and hot air later this week and next weekend, the northern Intermountain regions may have the wildfire risk increase.

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