Grasshopper’s Weekly North American Forecast – 20th December

December 20th, 2019

 

Source: windy.com

 

Mountainwatch | The Grasshopper

North American Forecast – Big totals in Canada and the Cascades, and a White Christmas in the American Rockies

Wednesday 18thDecember (Pacific Time)

In the last couple of weeks we’ve seen snowfalls from half to a whole metre or more over the Sierras and central American Rockies.

This week the action shifts north, and resorts in Canada, the Cascades and the north of Idaho and Montana will receive a whopping 35-75cm (including Wednesday snowfalls), with 1m+ expected on more exposed terrain. It’s a timely dump too, because these are the areas that are well below average and are screaming for snow.

The Sierras will get in on the action on Sunday with a tidy top-up. Then the southern portion of the American Rockies demand their two cents Tuesday into Christmas day with some decent totals showing up.

 

Thursday-Sunday

While high pressure sits over the American Rockies, another one of those deep lows will churn away in the Gulf of Alaska. A moist southerly flow will push moderate to heavy snowfalls onto Canadian resorts, the Cascades, and the north of Idaho and Montana during Thursday.

While snowfalls ease to showers over the Coast Mountains during Friday, before clearing Saturday, the Pineapple Express will set up and keep pumping snow over the Cascades and the southern Rockies of Canada, where it’ll eventually clear Sunday. As usual, the Pineapples Express will bring an airmass that is rather mild, and we can expect rain and slush at lower altitudes.

Also on Sunday, the Sierras will get in on the action as the frontal system (formerly the pineapple express) meanders southwards, with 10-25cm expected.

 

Monday-Wednesday

After scattered snow showers over the Sierras, Idaho & Wyoming during Monday, low-pressure will spring up where there was once high pressure over southern half of the American Rockies during Tuesday.

This scenario is a little iffy at this time, but we could see moderate to heavy snowfalls over resorts in Arizona, New Mexico, Utah and Colorado, which will eventually peter out on Christmas day. All up we could see 15-25cm in these places but up to 40cm for mountains in the south of Colorado.

That’s all folks. I’m coming at you every Thursday with all the highlights and snowlights for the week, but be sure to check in between times for on-the-ground reports and other great articles.