Big Picture:

A trough of low pressure will be located near the West Coast during the first half of this week, and a series of shortwaves rotating through the trough will favor showers and thunderstorms across the Northern Rockies. 

By late in the week, the trough will start to move across the Intermountain West with thunderstorm coverage increasing along the eastern slopes of the Continental Divide.

Forecast for Monday Afternoon/Monday Night:

Showers and thunderstorms have developed across the Sierra, Cascades, Great Basin, Northern Rockies, and Western Canada on Monday with activity expected to persist into early Monday evening.

Isolated storms are also possible across the San Juans in SW Colorado as well as Northern New Mexico, but minimal lightning activity has been detected across this region so far as of mid-afternoon Monday. 

Forecast for Tuesday:

More widespread showers and thunderstorms can be expected across the Northern Rockies as a shortwave moves through, with locally heavy rain possible across Central Idaho and Southwest Montana. Scattered showers and thunderstorms will also develop across the Washington Cascades and Western Canada, with more isolated coverage and lighter rain further south into Oregon and California.

We could also see isolated thunderstorms across Southern Colorado and Northern New Mexico, as well as Northern Utah.

Forecast for Wednesday:

Another active day is in store for the Northern Rockies with shower/thunderstorm coverage and rainfall amounts favoring Central Idaho and Western Montana the most. Meanwhile, areas east of the Divide in Wyoming and Northern Colorado could also get in on the action, while a drying trend is expected across Southern Colorado and New Mexico.

Further west, an approaching shortwave will result in an uptick in thunderstorms from the Sierra to Northern Utah, while the Northern Cascades and Western Canada will also see more showers and thunderstorms.

Forecast for Thursday to Friday:

The trough of low pressure will finally start to move eastward late this week with scattered thunderstorms expected across the Central Rockies, while an uptick in activity is also expected across Eastern Wyoming and Eastern Colorado.

Further west, a drying trend will occur across the West Coast and temperatures will also start to heat up as a ridge of high pressure builds. 

Outlook for Saturday (July 1) to Thursday (July 6):

The pattern during this period will feature a strong ridge of high pressure along the west coast of North America with dry conditions expected. However, a northwest flow east of this high pressure ridge is expected to set up across the Central and Eastern Rockies, keeping thunderstorm chances in the picture. 

There is a high probability of hotter than average temperatures across the Far West and really much of the Intermountain West on the western side of the Continental Divide. In other words, it's going to feel like summer.

Below-average temperatures are favored near and east of the Continental Divide in Wyoming, Colorado, and Northern New Mexico. 

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

Alan Smith