Deep snow is within top confidence levels for upper elevations of the Pacific Northwest (Coastal and interior), BC (Coastal and interior), and the Panhandle of Idaho. The hardest part about putting out a deep forecast is the value in chasing with low snowpack in some areas and a flip flopping of snow levels from cold to warm. The further north you go, the better the odds of medium cream or occasional medium to heavy density powder especially for the interior of BC where temps will be slightly cooler.
A weak system is making it's way into the northern Sierra today that might land 3-5 inches for many resorts by late Wednesday. An atmospheric river sets up over the Pacific Northwest this week with the heaviest moisture due late Thursday night into Friday (Warming trend). Temps in the PNW start out cold Thursday with light to moderate snow likely (Decent quality) perhaps 3-8 inches (Northern areas are favored). If you stick to groomed runs in Washington Thursday morning you might actually grab a decent line with some new medium density snow. Do it now, before the temps warm Thursday night and Friday! The GFS is showing decent amounts in Oregon and areas south where the Euro keeps the bulk of moisture north. Central Idaho will also benefit on Thursday with some moderate snow possible on the western sections of the State extending slightly south into Ketchum (Lighter snows).
The Atmospheric River cranks hard Thursday night into Friday impacting the Cascade Range with 1-2 feet of wet snow above 5500 feet in the southern regions and 4500 feet further north. The summits of most ski resorts will be digging out Friday morning as snow continues to fall heavily in many areas. The GFS is bullish for Oregon while the Euro is showing less (12-15). 2-3 feet is possible through Friday night on the summits of the Mount Baker Ski area with 2 feet likely further south near Stevens Pass, Crystal Mountain, and White Pass. 9-15 inches is likely further south into the Oregon Cascades. The Good: Decent powder Thursday with colder temps (Stick to the groomers). Heavy snow Thursday night-Saturday (Base building). The Bad: Warming trend Thursday/Friday with rain at the bases of many resorts while heavy dense snow falls from mid mountain to the summits. Slightly cooler in the northern areas. Cooling trend Saturday/Sunday with light snow still falling may offer the best conditions with some fluff on top of the cream that falls Friday.
The northern Panhandle of Idaho including Schweitzer will see very heavy snowfall Friday/Saturday with snow levels in the 5K to 5500 foot range. Temps cool late Saturday morning and Sunday with some additional lighter accumulations. Whitefish Montana may also squeeze out some wet freshies at upper elevations late this week.
Whistler will also benefit from mid mountain to the summit with an additional 1-2 feet likely at upper elevations. Rain will likely be falling at lower elevations.
Interior BC cranks out in a big way especially Friday-Sunday. Moderate to heavy snow is likely for much of the interior of BC this weekend. Its possible that even higher amounts, perhaps 20-28 inches focuses on areas just north of the Montana and Idaho borders in southern BC. Snow levels will hover just above the valley floors of most resorts before lowering somewhat late Saturday/Sunday. Resorts in southern BC will be deeper than areas to the north.
Below: Total snowfall for the interior of BC, northern Idaho and Montana through Saturday morning (Upper elevations).
Is this all chase worthy? That is the magic question. For Deep cream, head to the PNW or perhaps Whistler this Friday/Saturday. For medium to heavy density powder perhaps interior BC offers a better compromise. The Panhandle of Idaho may offer a solution at the summits Friday or Saturday. There is no single good answer. This storm will offer game changing conditions to many of the PNW ski resorts, including Whistler (Base building).
Models are in disagreement for a Sierra storm due on Sunday/Monday. The GFS has advertised a moderate system of perhaps 8-12 inches for this time period. The Euro is a bit more pessimistic. I think it's likely that some snow will be falling over the higher passes of the Sierra late this weekend. Sunday or Monday are likely candidates for some powder for much of the Sierra range.
Below: Ensembles showing a trough entering the coast of California as early as Sunday/Monday.
The long term ensemble runs hint at the Sierra system dropping south to the Baja of Mexico before possibly swinging up into the southern or central Rockies during the holiday timeframe. Its too far out to gain confidence, but areas that could be favored are the 4 corners and hopefully extending north into the central Rockies.
Below: XMAS Day shows the trough advancing south and east. The operational models which have low confidence a week away show 2 options. The GFS digs this low far south away from many of our ski areas, where the Euro shows it impacting the 4 corner resorts mid next week. Confidence will increase as we approach the 3-5 day range.
Enjoy the powder-cream, and thankfully the PNW will begin to base build this week.