A Pacific storm system is moving east of the Rockies on Monday after bringing welcome moisture to portions of the Pacific Northwest and Northern Rockies along with cooler temperatures.

Temperatures are quite comfortable across the Northern Rockies behind the passage of a cold front with afternoon highs expected to be well below-average. 

As nice as this cooldown was, it will be short-lived. A strong ridge of high pressure will build over the West Coast in the days to follow and a heatwave will take hold from California to British Columbia.

The Pacific Northwest in particular will see the hottest temperatures relative to average from Wednesday through Friday – though not to the extent of the record-breaking heat experienced in late June. 

Last weekend, smoke issues and poor air quality were widespread across much of the West as strong westerly winds aloft transported smoke from California fires into Nevada, Utah, Idaho, Wyoming, and Colorado.

On Monday, air quality has improved in the north, but remains poor from California to Colorado.

Taking a look at the smoke forecast map, we can see the largest fires are present over Northern California, with a handful of less intense fires (relative to CA) ongoing across the Northwest.

Forecast Smoke (surface)

Forecast Smoke (sky)

Current Air Quality

From Tuesday through Friday, prevailing winds over California and the West Coast will transition from westerly to southerly, and this will begin to drive the heaviest smoke northward rather than eastward. By Thursday and Friday, western portions of Oregon and Washington (areas with previously clean air) will likely see smoke arrive in this pattern. 

Meanwhile, smoke conditions should improve somewhat in Utah and Colorado, though all areas of the Rockies and Interior Northwest will see varying degrees of smoke and haze, both from "recycled" California smoke entrained in the atmosphere along with smoke from Northwest wildfires. 

Forecast for Monday, August 9th

Monsoon moisture is moving back into Arizona from the south on Monday, which scattered thunderstorms and wetting rains expected across southern and central portions of the state, along with Southeast New Mexico. The rest of the West is looking dry.

Forecast for Tuesday, August 10th

Monsoonal moisture will continue to increase across the Southwest on Tuesday with thunderstorm activity spreading into New Mexico, Northern Arizona, the SoCal Mountains. A few storms are possible east of the Divide in Colorado, but it should remain pretty quiet across the higher terrain by early August standards.

Forecast for Wednesday, August 11th

Scattered thunderstorms with wetting rains can be expected across New Mexico, Arizona, and the SoCal mountains, with more isolated and drier thunderstorms extending north into the Sierra, Southwest Utah, and southern/western ranges of Colorado. 

Forecast for Thursday, August 12th

There will be a slight shift in thunderstorm activity eastward across the Southwest with fewer storms in California and an uptick in storms across New Mexico. Thunderstorm coverage will increase slightly over Southern and Central Colorado as well though rainfall will be light. A few isolated storms are possible north into Wyoming and Montana as well. 

Forecast for Friday, August 13th

Another active day is expected across Arizona and New Mexico on Friday, while Colorado will also see a more noticeable uptick in thunderstorm activity. A cold front sliding into Eastern Colorado will also result in better chances for thunderstorms across the Front Range mountains and foothills.

Outlook for Sat, Aug 14th - Wed, Aug 18th

Saturday's pattern will remain similar to Friday's, then the pattern will turn more active overall from Sunday through the first half of next week as high pressure breaks down and the jet stream dips into the Northwest U.S.

Energy from the jet stream will interact with increasing monsoonal moisture to result in more numerous thunderstorms across the Rockies in particular. Temperatures will also cool off across most areas, and especially in the Pacific Northwest.

Thanks so much for reading! Next update on Wednesday (8/11).

ALAN SMITH

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