Forecast for Monday Afternoon/Monday Night:

A trough of low pressure centered over the Pacific Northwest has resulted in wet conditions and well-below-average temperatures across the Northwest and Northern Rockies on Sunday and Monday. 

High temperatures on Monday will range from 15 to 30ºF below average across a large portion of the West. The chilly air has also resulted in lowering snow levels, and snow has been accumulating down to ski resort elevations across the Pacific Northwest and Western Canada. 

The heaviest and most widespread rain/snow on Monday and Monday night will be across BC and Western Alberta, which is great news and should help with fire conditions.

Widespread showers will also continue across the Cascades and Central Idaho, while a band of moisture will continue to result in rain across Northwest Wyoming and South Central Montana. Northern Utah will get in on the action as well.

The chilly airmass will minimize the lightning risk across much of the Northwest. The best chance of lightning will exist across Northern Utah as well as Southern Montana/Northern Wyoming areas east of the Continental Divide. 

Forecast for Tuesday:

The trough will be moving east on Tuesday and associated precipitation will gradually transition eastward as well. Southeast BC, Western Alberta, and portions of Central Montana/Wyoming will be favored for the most widespread showers.

The Cascades, Idaho, Western Montana, and Northern Utah will see comparatively lighter and more intermittent showers, but cool/wet conditions will prevail. Higher elevation areas across the Northwest and Northern Rockies will continue to receive light snow accumulations as well.

The best chance of thunderstorms will be east of the Divide in Wyoming with lesser chances in the colder airmass further west. 

Forecast for Wednesday:

A cold front will slide down the eastern side of the Continental Divide with upslope winds focusing shower and thunderstorm chances along the eastern slopes and adjacent plains of Montana, Wyoming, and Colorado. Showers will become lighter and more isolated across Washington, Idaho, and Western Montana with a bit more coverage north of the Canadian border.

Forecast for Thursday to Friday:

On Thursday, a new trough of low pressure moving into California will result in a chance of showers/thunderstorms across the Sierra with light showers also expected across the Cascades and BC. Further east, an active thunderstorm day is likely near and east of the Divide in Colorado and Southern Wyoming.

On Friday, showers and thunderstorms will become more widespread across the Northern Rockies as the trough moves across the area, while storm coverage will become more isolated in Colorado. Heavy rain will also be a possibility across parts of Montana, especially east of the Divide where Gulf of Mexico moisture will be a factor.

Outlook for Saturday (June 24) to Wednesday (June 28):

Moisture will linger across parts of the Northern Rockies, especially Montana, on Saturday. A brief drying trend is then expected after that, followed by increasing chances of showers across the Northwest and Northern Rockies during the week of June 26th.

Meanwhile, a dry pattern is expected to take hold across the Southwest, as well as Utah and Colorado. 

Temperatures are generally expected to be warmer during this period compared to the prior week, though California is still favored for below-average temperatures. Warmer than average temperatures are expected across the Pacific Northwest as well as New Mexico, while the Central Rockies and Great Basin should not deviate far from average. 

Thanks so much for reading! Next update on Wednesday (June 21).

Alan Smith