Skiing Weatherman: Pattern Change Continues

The Vortex Is Coming.

Last week I discussed a major pattern change that would unfold over North America this month. As we hit the midpoint of January, those changes are well underway. An episode of stratospheric warming over the far northern reaches of the hemisphere has matured in typical fashion, leading to the displacement of the polar vortex away from the North Pole. One chunk of the vortex’ cold air has descended into Asia, with another pushing into Europe, causing a 20 inch snowfall in Madrid! North America is next in line as the jet stream reshapes itself and changes the prime source region of air for the U.S. from the Pacific to the Yukon and Arctic regions. Here is the current jet stream set up…

If you start in the eastern Pacific and head inland you will see that all the way from British Columbia to the Baja, the air flowing onto the continent is of Pacific origin. Maritime air masses can be cold across the far north, but overall, they are not friends of winter sports. Yes, they provide moisture but the relative warmth of the underlying body of water ensures that their chill is limited. This is the configuration that has dominated for several weeks and while the high elevations of the West have been able to convert most of the moisture to snow, further East, each storm of late has been battle for every snowflake. The deep trough that you see over the Midwest on this map has just enough cold air directed into its’ circulation from the north to promise some fresh snow this weekend from the northern Great Lakes eastward to New York and much of New England. Due to the presence of the blocking ridge over Quebec and Labrador, this system will linger into next week, leading to additional accumulations over the mountains of the Northeast.

Next week, a series of additional troughs will spin out of the trough over Alaska, crest the ridge that is building in western Canada, and track southeastward through the Lakes and into the East. One of those systems will split, with one piece continuing southeastward and another piece turning into the Southwest. Each successive disturbance will bring with it increasingly cold air masses. By the time we reach the 23^rd or so, the jet stream pattern will look something like this:

Now, if you start on the peak of the ridge north of Alaska and head south, you will see that the prime source region will be very different, and potentially very cold. With a trough covering much of the country AND with plenty of cold air involved, we will enter a stretch of weather when snows are frequent. The block over northeastern Canada will help to suppress the storm track enough so that the risk of lows that cut through the Great Lakes and bring mixed precip/rain to the Northeast will be limited. With the possible exception of the southern Appalachians, where the ridge over Cuba will push milder air northward, we are heading toward a pattern favorable for snow nationwide. Bring it!

Regional Details

Northwest U.S./Western Canada: Parade of storms resumes late next week as ridge axis eases offshore.

Sierra: West coast ridge keeps it mild and dry for a week. As ridge axis moves offshore, snow prospects improve late month.

Rockies: Northern resorts pick up fresh snow every few days. Fresh snow for central and southern resorts as upper air disturbance settles/develops over region.

Midwest: Pattern turns progressively colder and Clipper systems bring snow every few days. Lake effect snow supplements the Clippers.

Mid Atlantic/Southeast:  Northern resorts benefit from colder, snowier pattern. SW Atlantic ridge turns ii milder in southern Appalachians.

Northeast/QB: Weekend storm brings meaningful mountain snow. Pattern turns colder late next week, likely with new snow threat. Great conditions a solid bet by late month.