Big Picture:

A broad ridge of high pressure will be centered near the New Mexico/Texas border on Wednesday and Thursday. Monsoonal moisture rotating clockwise around the high pressure center will favor the Four Corners states and Southern Wyoming, with a little bit of moisture sneaking into the Northern Rockies on Thursday. 

Further north, the jet stream will remain in place over the Pacific Northwest. Gusty winds and dry conditions on the southern side of the jet will result in high fire danger from the Northern Great Basin into the Snake River Plain of Idaho, as well as portions of Western Montana. 

As far as temperatures go, the Pacific Northwest and Northern California will be cooler than average over the next 5 days, with above-average warmth across the Southwest, Southern California, and Central Rockies. 

Fire and Smoke Outlook:

Significant fires continue to burn across portions of Oregon, Idaho, Montana, and British Columbia. Northern BC as well as the Flat Fire in Oregon have seen reduced fire behavior recently thanks to cooler temps and higher relative humidity.

Fire activity has picked up a bit across Southeast BC and will result in heavy smoke and poor air quality at times across the Canadian Rockies. In the U.S., generally light smoke/haze can be expected late this week across portions of Oregon, Idaho, and Montana, with locally heavy smoke near and just downwind of fires.

Forecast for Wednesday:

Scattered thunderstorms can be expected across the higher terrain of the Four Corners states along with Southern Wyoming. Most areas will see hit-or-miss light to moderate rain with lightning posing the greatest threat, but stronger storms could produce locally heavy rainfall along with a risk of flash flooding in slot canyons and dry washes. 

Forecast for Thursday:

The Four Corners states will remain favored for thunderstorms with a slight eastward shift in moisture resulting in a relative uptick in thunderstorm coverage across Colorado and a relative decrease in coverage across Southern Utah and Arizona.

A trough moving into the Northwest will also transport some moisture into the Northern Rockies with scattered thunderstorms developing across Wyoming and Montana. Further north, Pacific moisture will reach Western Canada with scattered showers and thunderstorms expected across BC and Alberta. A few light showers may also reach the Northern Washington Cascades. 

Forecast for Friday:

Moisture will decrease a bit overall with scattered thunderstorms favoring the Colorado and New Mexico Rockies along with the higher terrain in Central Arizona. Further north, thunderstorm activity will be more isolated across Wyoming and Montana.

Isolated to scattered showers and thunderstorms will also impact portions of BC and Western Alberta, while areas south of the border in the PNW will stay dry.

Forecast for Saturday to Sunday:

Heading into the weekend, monsoonal moisture will gradually increase across the Four Corners states with scattered thunderstorms expected both days. Flash flood potential is also expected to increase across the canyon regions of Arizona and Southern Utah.

Easterly winds and lingering moisture along the eastern slopes of the Continental Divide in Montana and Wyoming will also keep thunderstorm chances going there.

North of the border, another trough of low pressure is expected to bring widespread showers to portions of Western and Central BC with more scattered showers/thunderstorms across Eastern BC and the Canadian Rockies.

Outlook for Monday (July 31) to Friday (August 4):

A significant uptick in monsoonal moisture is expected across the Southwest and Southern Rockies next week with moisture also reaching the Northern Rockies, and possibly extending westward into the Sierra Nevada Range.

The result will be an overall wetter pattern with more frequent thunderstorms and rainfall, along with the potential for frequent lightning, heavy rain, and flash flooding in vulnerable terrain.

We'll also have to keep an eye out on areas on the northern and western peripheries of the monsoon moisture plume, as these areas could be more prone to dry thunderstorms and high fire danger. 

The increase in moisture and cloud cover should take the edge off the heat across the Southwest, at least somewhat, though temps are still expected to run above average. Also, a noticeable warm-up is expected across the Pacific Northwest and Western Canada as high pressure ridging builds well to the north.

Thanks so much for reading! Next update on Friday (July 28).

Alan Smith