SUMMARY:
Significant game-changing snows move into the Northwest bringing several feet of perfect base building powder Thursday-Saturday. An atmospheric river of moisture will keep snow showers going (Waves of energy continue) in the PNW eventually moving over the north/central Rockies Thursday-Sunday. Several moderate to deep events will ensue in the Rockies with the coldest part of the storm not due until Saturday or Sunday. There will be many parts to this storm over the next 3-5 days.
FORECAST POW:
It's going to be a solid week of powder for many areas this week! The most notable highlights are in the Northwest, Western Idaho, Panhandle of Idaho, Tetons, Northern Utah, and eventually, Colorado who catches up slowly late this week with a Grand Finale late Saturday/Sunday.
Northwest: Snow starts late Wednesday night and continues into Friday morning. Initially, with SW winds, the northern Cascades such as Mount Baker will do best especially late Wednesday to Thursday (7-14). Snow levels start out near the bases so amounts at the summits will significantly vary initially before gradual cooling occurs Thursday PM-Saturday. Winds shift to the west on Thursday/Friday enhancing ongoing snowfall for the entire Cascade Range from Washington to Oregon. Models are all in agreement for 2-3 feet of medium to heavy density snow (Elevation-dependent) to fall over the entire Cascade Range. The highest amounts might end up at Mount Baker (Initially favored), followed by Bachelor in Oregon. All ski areas in the northwest including the Panhandle of Idaho will score much-needed deep snow! Cooling temps will bring snow to all base areas by Thursday afternoon.
Below: Total snowfall through Saturday in the PNW through Friday evening. Peak snowfall likely to be late Wednesday night in the northern Cascades followed by all mountain ranges Thursday-Friday.
ROCKIES/SIERRA
In looking for the best chases in the Rockies or Sierra, there are several options. Weak waves of moisture ejecting from the low pressure centered over the PNW will flow into Idaho and Wyoming initially Wednesday/Thursday. Moderate to heavier snow will be falling in Idaho late Wednesday night or early Thursday where light snow is likely in the Tetons initially. Heavier snow in Idaho on Thursday morning (Storm ski Brundage or Sun Valley), will hit the Tetons mid-Thursday morning with 6-10 inches likely by your last chair in the Cowboy State. The AM snow reports on Thursday may only show 2-5 inches in Wyoming with higher amounts in western Idaho. Temps will be on the warm side in the Tetons Thursday (32-33F in Jackson) with the highest amounts at the summits initially Thursday. (Much less at the bases- Targhee has elevation advantage at the base). A cold front crosses the Tetons late Thursday night into Friday with an additional 4-8 inches of good quality snow (colder) for your 1st tracks in the Tetons. There will be a break in the action Friday before another wave of moisture hits for Saturday (Storm ski) in the Tetons. Total snowfall in the Tetons through Saturday should be in the 12-20 inch range at the summits (Best ride times are late Thursday/Friday and again during the day Saturday).
Below: Total snowfall for Idaho through Friday morning. Most snow will begin falling in earnest late Wednesday into Thursday in Idaho.
The Sierra gets warm this week but deserves a mention for a cooling trend and likely snowfall (4-10) possible late Friday night into Saturday.
In Utah, the models are all bullish for significant snowfall for the entire Wasatch Range Thursday PM to Saturday. Initially, it looks like the northern Wasatch is favored with SW flow so look for deeper amounts from I-80 north late Thursday to perhaps Midnight. (Park City, Deer Valley, Snowbasin, Perhaps Beaver). Moisture drops further south through the day towards the Cottonwoods that will attempt to catch up on Friday. Winds shift to the West or Northwest early Friday enhancing snow intensities for much of Utah. Snow intensity might peak in the Wasatch Friday morning. It's possible that the northern Wasatch (Snowbasin Powder, Beaver, Park City) outperforms the south (Cottonwoods). Expect a general range of 8-12 inches for your 1st tracks on Friday with snow continuing during the day. There looks to be a break on Friday night with additional snow likely on Saturday (Moderate amounts).
Below: Total snowfall through Sunday for the Tetons, Wasatch, and northern Colorado. Southern Colorado and north/central New Mexico (Tao's wildcard) will be respectable Saturday night into Sunday.
For Colorado light to moderate snow will be falling Thursday night into Friday with a general 5-9 inches for most of the I-70 corridor. The highest amounts might land over the western side of the corridor towards Vail, Beaver Creek or Aspen. The AM reports Friday may only show 2-4 inches where the PM reports will be higher as it continues to snow moderately throughout the day (5-9 or more by 4 PM). There is a break on Friday night and early Saturday before a stronger push of cold air and moisture arrives Saturday PM to Sunday AM. That will favor the Southern Mountains initially (SW Winds). Silverton, Purgatory, Wolf Creek and Telluride are all going to score decent amounts Saturday night! Winds shift to the NW into Sunday allowing moderate moisture to flow into the I-70 corridor during the day. I am bullish for an additional 6-10 inches or more to fall in many areas of Colorado for your first tracks Sunday! While spots south of I-70 may have the highest amounts, all areas of Colorado will see respectable totals to ride POW.
Chases: You might be able to score Thursday pow in Idaho or Wyoming, Friday Pow in Utah or Colorado. On Saturday you can chase from Utah Saturday to Colorado for Sunday.
EXTENDED:
Early next week will most likely see a return of short-lived high pressure. Its likely additional storms start impacting the Pacific Northwest or Sierra by Wednesday or Thursday (December 18/19). The Euro keeps most of the moisture along the western coasts (Sierra or PNW) while the GFS ensembles show a more zonal flow of moisture streaming east towards the Rockies mid to late next week.
Below: The optimist - GFS ensembles for low pressure mid to late next week. The East may also get active.
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Enjoy the Powder everyone!
Powderchaser Steve
