Major cooldown eyes West as fire weather increases for Great Basin
A push of much cooler air will arrive in the West and will set off some high-elevation snow to go along with spotty thunderstorms and gusty winds that can raise the wildfire threat level.
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As a major heat wave builds and surges from the central United States to the East this weekend, much cooler air will lunge across the West, generating areas of gusty winds and also some shower activity with snow for some high elevations, AccuWeather meteorologists say.
Heat will continue over much of the Great Basin and Rockies, but cooling will evolve and become more pronounced late this week over the Northwest and will progress throughout much of the West over the weekend.
Temperatures will be slashed significantly over the interior West. For example, in Salt Lake City, after highs of 100-105 F from Thursday to Friday, highs on Saturday will be 25-30 degrees lower. It's possible temperatures on Sunday may reach only the 60s.
The temperature drop will not be as extreme along the Northwest coast, but it will turn much cooler. After highs in the lower 70s on Thursday in Portland, Oregon, highs are projected to be in the lower 60s on Friday and may not climb out of the 50s on Saturday.
It will get chilly over the passes in the Cascades, the Sierra Nevada and much of the northern Rockies. Temperatures at Snoqualmie Pass, Washington, will peak in the lower to middle 40s on Friday and Saturday with showers. Hikers should take note that in areas above the passes and over the high country, snow will mix in with a few inches possible over some of the ridges and peaks.
Where the sky is able to partially clear and winds drop off at night, there will be the possibility of some record lows being set, AccuWeather Meteorologist Danielle Ehresman said.
"Some locations over the interior West could challenge record low maximum temperatures and overnight record low temperatures," Ehresman said. "For example, on Sunday, in Billings, Montana, the record low maximum temperature of 61 set in 1967 could be rivaled, as well as the record Sunday night low of 43 set in 1960."
Just because much cooler air will move in does not mean there cannot be thunderstorms. The same pattern can trigger locally gusty thunderstorms that produce lightning strikes, which are another danger for hikers. Some of the storms can produce hail that covers the ground.
Cooler air will spill to the east of the northern and central Rockies by early next week. Following highs within a few degrees of 100 in Denver on Friday and Saturday, highs are projected to be in the mid-90s on Sunday but only in the 70s on Monday and Tuesday.
In general, much less pronounced cooling will reach the Southwest deserts, but temperatures will be shaved by about 10-15 degrees in Phoenix from Friday to Sunday. Highs in the 100s in Las Vegas through Friday will be swapped with highs in the mid-90s from this weekend to early next week.
Along the Southern California coast, highs in downtown Los Angeles will be mainly in the 70s this weekend, following a high well into the 80s into Friday.
As the cooler air moves in, a zone of gusty winds will accompany drier air over the interior Southwest from Thursday to Sunday. The wind, dry air and strong mid-June sunshine will cause fuels to dry out. Sparks from any lightning or human interaction can lead to rapidly spreading wildfires.
Multiple large wildfires were burning over the interior Southwest due to ongoing drought in the region.
The upcoming conditions can pose new challenges for firefighters, as many of these fires had minimal containment as of midweek.
Meanwhile, some moisture indirectly associated with Hurricane Erick near the Pacific coast of Mexico is forecast to bubble northward into the southwestern U.S. next week. The moisture surge should trigger at least an uptick in afternoon and evening showers and thunderstorms over some of the deserts and the southern Rockies.
The location of the plume of moisture will depend on how well Erick holds together as a rainstorm over central and northern Mexico.
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