Active Pattern for the West:

A large and slow-moving trough of low pressure will linger across the West for the remainder of this week and will gradually work its way inland over time. The result will be a wet and active pattern for many areas with high-elevation snow also expected. 

A ridge of high pressure over Eastern North America will result in warmer and drier conditions for most areas. The main exceptions will be the Mid-Atlantic/Ohio Valley, where weak disturbances will bring occasional showers. Areas near the coast may also see some showers as a system passes by offshore.

Snow accumulations will favor the higher terrain in Canada over the next 5 days, while mountain ranges throughout the Western U.S. will see high-elevation accumulations as well.

Rainfall over the next 5 days will be heaviest across the Pacific Northwest, while the Sierra, Great Basin, and Northern Rockies will receive significant rain as well. Precipitation will be more showery in nature across Colorado, New Mexico, and Arizona, with thunderstorms also possible.

Forecast for Wed (Sep 27) to Thu (Sep 28):

Rain and snow will favor the Pacific Northwest and Western Canada during this period, with Northern Idaho/Montana getting in on the action as well. Across the East, rain showers can be expected across the Central/Southern Appalachians.

Forecast for Fri (Sep 29) to Sat (Sep 30):

The Western storm system will continue to deepen to the south while also gradually moving eastward with rain/snow favoring the Northern Rockies both of these days. The Cascades will see a relative drying trend with fewer/lighter showers.

California and Nevada will also get in on the action on Saturday, with more widely scattered showers/thunderstorms developing in Utah, Colorado, and New Mexico. Further north, a storm will impact the Coast Range of Alaska with heavy snow expected.

Rain showers will remain possible across the Mid-Atlantic and Coastal New England on Friday before drying out on Saturday.

Forecast for Sun (Oct 1) to Mon (Oct 2):

The storm system will continue to impact the Sierra, Great Basin, and Rockies with snow for the higher elevations. Another storm will also reach the Northwest with rain and snow favoring Alaska and Northwest BC on Sunday and Southern BC/Northern Washington (with high snow levels) on Monday.

Outlook for Tue (Oct 3) to Sat (Oct 7):

Chilly temperatures and unsettled conditions will linger across the West during this period. The storm track looks to favor the Northern Rockies, with higher terrain in Interior BC, Alberta, and Montana having the best chances of accumulating snowfall, while occasional light rain/snow is possible elsewhere in the West, too.

The East will remain in a warmer and drier pattern with occasional rain showers possible.

Thanks so much for reading! Next update on Wednesday (October 4).

Alan Smith