Big Picture Weather Pattern:

The Northern Rockies (WY & MT) will see lingering moisture and showers from a departing low pressure system on Monday. Another low pressure system moving into British Columbia will bring another round of showers to Washington and the Far Northern Rockies Monday-Tuesday.

Monsoonal moisture will retreat southward as a cold front moves across Colorado. Moisture will be primarily limited to New Mexico and Eastern Arizona where high thunderstorm potential is expected, with only isolated activity for the southern ranges of Colorado. 

5-Day Temperature Outlook:

The Northern Rockies will remain on the cooler side of average this week, but a warming trend is in store for the West Coast and Arizona with temperatures rising above average.

Forecast for Mon (Aug 26) to Tue (Aug 27):

The heaviest rainfall early this week will favor the Olympics and North Cascades in Washington, portions of Southern Montana and Wyoming, and New Mexico and Southeast Arizona. Colorado hangs onto thunderstorm chances, but activity will be isolated and will favor southern and western parts of the state.

Pacific Northwest:

Rain showers will develop over the Olympics and Cascades in Washington on Monday afternoon and Monday night, with more isolated activity extending into the Northern Oregon Cascades. Showers linger into Tuesday morning, with some light activity reaching NE Washington and Northern Idaho. 

Northern Rockies:

Showers will linger over portions of Wyoming and Southern Montana (favoring areas near and east of the Continental Divide) on Monday before tapering off on Monday night. Showers will also develop over West Central and NW Montana on Monday night and Tuesday as a system passing to the north brushes this area.

New Mexico:

An uptick in moisture will result in fairly widespread coverage of thunderstorms on Monday and Tuesday with locally heavy rain possible. The Sangre de Christo Range including Taos southward to the Sacramento Mountains around Ruidoso will be favored, as will southwest portions of the state.

Arizona:

Thunderstorm chances will largely be confined to Southeast Arizona with locally heavy rain possible, while Northern Arizona (Flagstaff, Grand Canyon) looks dry. 

Forecast for Wed (Aug 28) to Thu (Aug 29):

The Northwest will dry out and warm up, while monsoonal moisture will keep thunderstorm chances going across New Mexico, Arizona, and Southern Colorado (San Juans and Sangres). Light showers are also possible across Montana on Wednesday, but confidence is low.

Forecast for Fri (Aug 30) to Sat (Aug 31):

New Mexico, Arizona, and Southern Colorado will continue to be the favored areas for thunderstorms, but we will also see a little bit of monsoonal moisture spread into Southern Utah, Nevada, and the High Sierra in California, resulting in isolated thunderstorms for these areas. 

Outlook for Sun (Sep 1) to Thu (Sep 5):

Summer will make a comeback as we head into early September with above-average temperatures expected for most of the West, except New Mexico where temperatures will be near average.

A weak low pressure trough over the West Coast will help to draw monsoonal moisture northward into Utah, Colorado, and the Northern Rockies, resulting in a better chance of thunderstorms for Sunday-Monday of Labor Day weekend (and possibly in the days to follow). The Cascades/PNW could also see enough moisture for shower and thunderstorm chances. 

Thanks so much for reading! Next update on Wednesday (August 28).

Alan Smith