Wet Pattern with High Snow Levels for the Northwest

Subtropical moisture has reached the Northwest this week, bringing rain to the Cascades, BC Coast Range, and low to mid-elevation terrain in the Northern U.S. Rockies. The most recent storm on Thursday did manage to produce some snow across the Interior of British Columbia, with Whitewater's snowstake cam indicating 10-15 cm (4-6") of new snow as of Thursday PM.

The storms impacting the Northwest have involved atmospheric rivers (AR) – long, narrow plumes of moisture originating way out in the Pacific. The next AR will impact the Northwest on Friday and Saturday with the amount of water vapor in the atmosphere exceeding 200% of average in some areas.

Forecast for Fri (Nov 3) to Sat (Nov 4):

Heavy rain will fall across the PNW and Cascades again on Friday and Saturday, while the Northern Rockies and Canadian Interior will see valley rain and high-elevation snow. Higher terrain in the Tetons as well as the BC Powder Highway region have the best chances of picking up decent snowfall totals.

Forecast for Sun (Nov 5) to Mon (Nov 6):

Storms will continue to impact the Northwest during this period, but cooler air will start to filter into the region with snow levels gradually lowering. This will result in an eventual change-over to snow down to ski resort elevations (at least the upper portions) in the Cascades.

Forecast for Tue (Nov 7) to Wed (Nov 8):

The final in a series of storms will track across the Western U.S. though considerable uncertainty exists regarding the storm track. Overall, the storm looks a bit weaker than previous storms, but colder air will be arriving, which will mean lower snow levels. Also, the storm should track a bit further south with the Central Rockies and possibly the Sierra getting in on the action.

Elsewhere, active weather is expected across a large portion of North America. Snow will return to Southeast Alaska as a strong storm arrives. Across the East, a storm will bring rain to New England on Tuesday with possibly some snow mixing in across the higher elevations. A storm is also expected in the Great Lakes on Wednesday with a mix of rain and snow.

Outlook for Thu (Nov 9) to Mon (Nov 13):

Confidence is low in how things will shake out in the West late next week as longer-range models are in poor agreement. The Northwest seems to be the most likely area to receive more moisture, with cooler air possibly supporting a better chance of snow at ski resort elevations. Storm potential for the Rockies is less certain.

Across the East, a more active pattern is expected including some potential for snow in New England late next week. 

Thanks so much for reading! Next update on Wednesday (Nov 8).

Alan Smith