Big Picture:

There are two main weather features that will impact the West this weekend. First, a trough of low pressure will move across Colorado on Friday and Saturday, resulting in widespread showers and thunderstorms both days before drying out on Sunday.

Meanwhile, a larger trough of low pressure originating in the Gulf of Alaska will deepen across Western Canada and the Northwest U.S. over the weekend and into early next week, resulting in a cool and wet pattern from the Cascades to the Northern Rockies.

Forecast for Friday:

Showers and thunderstorms will favor Colorado and Wyoming with locally heavy rain possible, especially east of the Divide in Colorado. Isolated to scattered thunderstorms can also be expected further west from the Southern Sierra to Southern Utah/Northern Arizona.

Rain will also fall across Western and Central BC on Friday with light showers developing across the Washington Cascades on Friday night.

Forecast for Saturday:

Colorado will see one more active day with scattered to widespread thunderstorms on Saturday. However, the threat of heavy rainfall will be lower compared to prior days. Further north, scattered showers and thunderstorms can be expected across the Northern Rockies, Western Canada, and Inland Northwest with generally light showers across the Cascades. 

Forecast for Sunday:

Showers and thunderstorms will become more numerous across Idaho, Montana, and Western Wyoming with locally heavy rain possible. Heavier and more widespread showers can be expected across the Cascades during this period, while BC and Alberta will also remain wet.

Colder air will also be arriving during this period with snow expected across the higher elevations of the Cascades and BC/Alberta, including the potential for heavy snow across the Canadian Rockies.

Further south, Colorado will finally see a break in the action with mostly dry conditions. The Four Corners, Nevada, and California are also expected to see dry weather.

Forecast for Monday to Tuesday:

Cool and wet conditions with widespread showers can be expected throughout the Northwest and Northern Rockies during this period along with the potential for significant rainfall totals. In addition, colder air will continue to work its way southward and eastward with high-elevation snow expected. 

Outlook for Wednesday (June 21) to Sunday (June 25):

By Wednesday or Thursday, the previous low pressure trough across the Northwest will exit to the east. However, additional weaker systems are projected to track across the Northwest and Northern Rockies with additional showers possible at times.

An uptick in showers/thunderstorms is also possible east of the Divide from Montana to Colorado, with drier conditions expected across the Southwest and California.

Temperatures are expected to remain cooler than average across a large portion of the West, with the notable exception being New Mexico where warmer-than-average temperatures are expected.

Thanks so much for reading! Next update on Monday (June 19).

Alan Smith