Big Picture:

There are two main weather features in place across the West early this week.

First, a powerful trough of low pressure is spreading rain and cooler temps into Cascades and Western/Central British Columbia, which is good news as this area needs the moisture. However, the Interior Northwest will be on the dry and windy side of this system and will see high fire danger early this week as a result.

Second, a ridge of high pressure will remain over the Southern Rockies with above-average temperatures continuing across a large portion of the West. Monsoon moisture will rotate around the center of high pressure, resulting in varying levels of thunderstorm activity across the Rockies and Southwest this week.

Fire and Smoke Update:

Fire activity is gradually picking up across the Northwest U.S. with large and active fires currently ongoing in Oregon, Idaho, and Montana. Fires continue to burn in BC as well, though cooler/wetter weather should help out with firefighting efforts this week.

Consistent southwest winds will result in light to moderate smoke at times across portions of Oregon, Washinton, Idaho, Montana, and Western Canada, with locally heavy smoke near and just downwind of the fires.

Forecast for Monday Afternoon/Monday Night:

Rain showers will continue across Western Washington and BC through Monday night with the heaviest amounts expected across Vancouver Island and the BC Coast Range. Scattered showers and thunderstorms can be expected over the BC Interior.

Monsoonal moisture will result in scattered showers and thunderstorms across Arizona, Utah, Nevada, Idaho, Western Wyoming, and SW Montana with a few storms also possible in the Sierra Nevada Range. Limited thunderstorm activity can also be expected across the Colorado Front Range.

Most areas will see a mix of wet and dry thunderstorms with some potential for flash flooding in slot canyons and dry washes in Arizona and Utah. 

Forecast for Tuesday:

Widespread showers will continue across the BC Coast Range on Tuesday with scattered showers and thunderstorms over the BC Interior. Lighter showers will continue across the Cascades and Olympic Peninsula with temperatures running below average.

As the trough moves across the Northern Rockies, monsoonal moisture will become suppressed further south, mainly impacting the Four Corners states where scattered thunderstorms can be expected favoring the higher elevations. Slot canyon flash flooding will be a possibility in Utah and Arizona. 

Forecast for Wednesday:

Monsoonal moisture will increase across Utah, Colorado, and SW Wyoming with scattered thunderstorms expected. A few dry thunderstorms are possible further north in Montana as well. Storm coverage will be more isolated further south over Arizona and New Mexico with storms favoring the higher terrain. 

Locally heavy rain and isolated flash flooding will be possible in slot canyons and dry washes of the Southwest, while cloud-to-ground lightning will be the greatest concern for alpine hikers and climbers in Colorado and across the Southern/Central Rockies. 

Forecast for Thursday to Friday:

A weaker trough will move into the Northwest during this period with monsoonal moisture spreading into Northern Wyoming and Southern Montana, while the Colorado Rockies and Southwest will continue to see daily rounds of thunderstorms. Utah should see a drying trend as the bulk of the moisture moves eastward. 

North of the border, the mentioned trough will spread more moisture into Southern BC where scattered showers and thunderstorms can be expected, along with the potential for locally heavy rain. Showers and storms can also be expected across the Canadian Rockies in Alberta.

Outlook for Saturday (July 29) to Thursday (August 3):

The monsoon is expected to intensify during this period with thunderstorm activity favoring the Southwest/Southern Rockies initially, while moisture should also increase across the Northern Rockies with increasing thunderstorm chances by later in the period. 

Temperatures are expected to remain below average across most of the West, though areas that see significant moisture could see the edge taken off of the heat at times. The California Coast, Central Valley, and NorCal are also expected to see some heat relief with near-average temperatures. 

Thanks so much for reading! Next update on Wednesday (July 26).

Alan Smith