Big Picture:

Lingering monsoonal moisture from last week's northward surge remains across the Northwest and Northern Rockies early this week. A series of low pressure troughs will continue to move across this region, resulting in frequent showers and thunderstorms with locally heavy rain.

Dry and breezy conditions will prevail across Southern Utah and Southern Colorado. However, monsoonal moisture is returning to Arizona and to a lesser extent New Mexico. This moisture push, while not particularly strong by local standards, is being aided by Post-Tropical Cyclone Eugene in the Eastern Pacific.

The mentioned features are helping to keep high pressure and its associated heat further south and east, with below-average temperatures expected across most of the West over the next 5 days. In other words, a nice break from the summer heat for many areas. 

Fire and Smoke Update:

Smoke is impacting portions of the Inland Northwest on Monday. However, increasing west/southwest winds along with cooler and wetter conditions should push most of the smoke out of this area with improving air quality by Tuesday.

An overall reduction in fire behavior is expected across the Northwest U.S. early this week with more active fires burning across Southeast BC. Further south, a few fires are burning across Northern Arizona and Northern New Mexico where conditions have been drying out.

Forecast for Monday Afternoon to Monday Night:

The Inland Northwest will be the favored region for showers and thunderstorms through Monday evening with locally heavy rain and isolated flash flooding possible. Shower activity will be on the decrease across the Cascades. Southern Idaho as well as Montana and Wyoming will continue to see showers and storms through Monday night as well.

Further south, isolated thunderstorms are possible across Northern and Eastern Colorado. An uptick in monsoonal moisture will also result in more numerous storms across Arizona and Western New Mexico with locally heavy rain possible. 

Dry and windy conditions across Far Northern Arizona, Southern Utah, and Southwest Colorado will result in increased fire danger.

Forecast for Tuesday:

Showers and thunderstorms will be more numerous across Wyoming and parts of Northern Utah, Eastern Idaho, and Southern Montana. More isolated activity can be expected across Northern Idaho/Western Montana and across Northern Colorado.

The next approaching low pressure trough from the Pacific will take a more northerly track with rain developing across Western and Central BC with a few light showers making it into NW Washington on Tuesday night.

Across the Southwest, scattered thunderstorms can be expected across the higher terrain of Arizona and Western New Mexico. Northern Arizona, Southern Utah, and SW Colorado will continue to see an elevated risk of wildfires, with the potential for dry thunderstorms also becoming a factor.

Forecast for Wednesday:

The next system will result in more widespread showers and thunderstorms across the Washington Cascades as well as Southern BC. Scattered afternoon and evening thunderstorms can also be expected from Central Idaho into Southwest Montana.

Moisture associated with the monsoon as well as Post Tropical Storm Eugene will continue to result in a good chance of thunderstorms across Arizona with some of this activity potentially sneaking into SoCal.

Forecast for Thursday to Friday:

The Northwest and Northern Rockies will see a drying trend during this period aside from some lingering activity on Thursday. Meanwhile, the monsoon will become more well-established across the Southwest with an increase in thunderstorm coverage expected across the Four Corners states, as well as Nevada and the higher terrain of California.

Outlook for Saturday (Aug 12) to Thursday (Aug 17):

A drier pattern is expected across the Northwest and Northern Rockies during this period. Monsoon moisture should result in more frequent thunderstorm activity across the Four Corners states, though rainfall is expected to be near to below average overall for this time of year. 

Summer warmth is also going to return to most of the West during this period. Above-average temperatures are expected across the Southwest and West Coast, while near-average temperatures can be expected across the Central Rockies.

Thanks so much for reading! Next update on Wednesday (August 9).

Alan Smith