Summary:

A weak system moves in tonight with a few snow showers possible.  However, all eyes are on an atmospheric river event that will bring copious snowfall to the high elevations of the Wasatch during the Saturday night thru Monday night time frame.  Another, colder storm likely for Christmas Day!

Details:

Lots to talk about!  Let's dive right in...

Friday night - Saturday morning: A weak shortwave will move through the region tonight.  It looks very weak on the models, but like we saw yesterday morning, these weak little guys can surprise us this time of year. Certain areas could pick up a quick couple inches of snow.

Saturday night - Monday night: A very persistent atmospheric river develops over the region.  This will bring copious moisture to the area for a long time frame.  Model QPF in the NAM through Tuesday:

 

The dark brown areas along the Wasatch spine indicate greater than 2" of liquid.  It has a lot of potential!

The big disclaimer with this atmospheric river is the snow levels.  This moisture has warm origins and not a lot of cold air to work with. Snow levels should rise quickly after the start of the event and reach close to 7,500 feet during the day on Sunday... Perhaps rising even higher than that at times.  That means that some of the lower base elevations like Park City/Snowbasin/etc, could see rain at times.  The upper mountains and the Cottonwoods should be all snow, however it will be high density, wet cement.  Very good for base building, but not so good for skiing.  Make sure you wear gore-tex if you're up there on Sunday or Monday.  The one other disclaimer is wind.  We are going to be near the jet stream, therefore high winds will accompany this event.  I'd expect northwesterly winds at ridge tops to gust up to 75mph during the event.

As for amounts, that is a tough call because the areas that will be favored will just see non-stop snowfall while other areas may only see occasional snowfall.  Also, with the high snow levels, the upper mountain will see much more snow than lower mountain elevations.  Overall, my initial estimate thru Tuesday is 18-26" for the Cottonwoods, 8-12" for Park City above 8k feet, and 18-30" for the highest elevations north of I-84.  Again, I don't expect this much at the base of most resorts, this is for the upper mountain where it will be all snow and better ratios.

Again, the skiing/riding could still be very good.  But this storm's biggest benefit will be to drop a base and get more terrain open!

Tuesday - Wednesday morning: A break in the action as the AR retreats northward.  There still could be some lingering showers but nothing major.

Wednesday night - Christmas Day: The next storm moves into the area.  This system is colder and more progressive.  It should move through the region quickly but there is a good chance it brings snow to all elevations -- with a decent powder day for the mountains!

Overall, it looks like the next 7 days will be a Christmas feast...

Long range:

Models are waffling a bit on what happens after Christmas.  The GFS gives us a break, the latest EC has another system dropping down from the north.  There is some suggestion that we undercut the ridge with the southern Jet by around New Years Day.  That would bring a very El Nino-like pattern to the west.  We'll see...

Evan | OpenSnow