Big Picture:

Two main areas of high pressure will be located over the Desert Southwest near the US/Mexico border and across Western Canada, while a trough will be located over the North Central U.S. In between these features, moisture and energy will favor the eastern slopes of the Continental Divide as far as thunderstorm activity goes.

Smoke from Northwest Canada wildfires has reached the Pacific Northwest this week, which has resulted in hazy skies and moderate to poor air quality. Smoke is expected to persist to varying degrees through Thursday or Friday before improving across the Northwest U.S. this weekend. 

Forecast for Wednesday Afternoon/Wednesday Night:

The Front Range, Sangre de Christo Range, and Eastern Colorado will be the most favored region for thunderstorms through Wednesday afternoon/evening.

Strong to severe thunderstorms will be possible across this region as well, especially south of Denver metro into the Southern Front Range/Sangres and out onto the plains. Large hail will be the main threat with stronger storms while damaging straight-line winds and tornadoes are also a threat.

Elsewhere, isolated thunderstorms will be possible across Wyoming, Montana, Western Canada, and the Northern Washington Cascades while the rest of the West looks dry.

Forecast for Thursday:

Thunderstorm coverage will increase a bit across Western Canada and the Northern U.S. Rockies with a few isolated storms also possible across Washington. The Front Range and Eastern Colorado will see another severe thunderstorm threat, with large hail posing the greatest threat while a few tornadoes are also possible, mainly east of the I-25 corridor.

Forecast for Friday:

A similar pattern will remain in place with isolated to scattered thunderstorms across Western Canada, the Northern U.S. Rockies, and Northern Cascades. Further south, the Front Range and areas near/east of the Divide in Colorado will see more numerous thunderstorms, including another threat of severe thunderstorms mainly across the Front Range foothills and eastern plains. 

Forecast for Saturday to Sunday:

No significant large-scale pattern changes are expected through Saturday with thunderstorm coverage favoring Western Canada, the Northern U.S. Rockies, and eastern ranges/adjacent plains of Wyoming and Colorado. A few isolated storms are possible across Washington & Oregon as well.

On Sunday, a drying trend is expected throughout the West as high pressure builds in from the south, with only some isolated thunderstorms possible near the Continental Divide. 

Outlook for Monday (July 10) to Friday (July 14):

High pressure will dominate the pattern across the Southern/Central Rockies, resulting in dry conditions across a large portion of the West with minimal thunderstorm potential. Weak disturbances are projected to track across the Northern Cascades and Far Northern Rockies, with occasional showers/thunderstorms possible.

The North American Monsoon is expected to remain dormant at least across the Western U.S. through next week. There are some signs of the monsoon circulation picking up across Mexico next week, with perhaps a weak monsoonal circulation reaching the Southwest U.S. during the week of July 17th based on long-range model trends. 

Temperatures are expected to be hotter than average across a large portion of the West during this period, though Eastern Wyoming/Montana are favored for below-average temps. Also, the West Coast from Washington to California is expected to see near-average temps in response to a weak trough out in the Pacific, which should result in cooler onshore flow. 

Thanks so much for reading! Next update on Friday (July 7).

Alan Smith