Friday, December 6, 2013
The very cold temperatures these last few days will moderate a bit later today and into the weekend as another surge of colder air drops into the western part of the large trough over the western US. This forces more southwesterly flow over our area by late tonight which should bring some noticeable warming to the mountain slopes. Valleys will remain cold.
That energy to our west will begin to move over our area by Saturday afternoon and will produce light to moderate snowfall through Sunday. While the absolute moisture in the air is low due to the cold temperatures, we may see some significant accumulations if the temperatures warm enough for the snow crystals called dendrites to form. Dendrites are the easily recognizable pointy star-shaped crystal that leads to very low density fluffy snow. If temperatures are too cold, as they are today, the snow crystals that form are more needle-like and pack together much more efficiently, leading to higher snow densities and denser snow.
Due to the snow continuing Saturday night and most of Sunday, I may expect a fluffly 6-12” on the hill by Sunday afternoon. The flow does finally turn to the northwest during the day Sunday which is constructive for snowfall, but moisture should be decreasing then partly offsetting the favorable wind direction.
A final dry trailing wave looks to cross the area early on Monday bringing another surge of arctic air into the area, but no snow. If skies clear Monday night, Tuesday morning could see the coldest temperatures of this event in the valleys as the fresh snow very efficiently cools the low-lying surfaces. However, mountain slope temperatures will begin to moderate as the week progresses, becoming noticeably warmer by Wednesday.
Another storm approaches the west coast near the end of the work week, though current model trends have this storm splitting and weakening as it enters the US.
Wednesday, December 4, 2013
I couldn’t bring myself to press glass with only a 7.5” overnight report, and caught the 10:40 am bus to see what was left. I was not planning on heading up to the -8F temperatures up top, but it was clear the powder hounds were out early this morning as all of the Four Points trails were very tracked. First run was in the upper parts of Closet and then a traverse over to Shadows, which is the usual for me. Good skiing, but not great as there was some crunchiness underneath from the sun this past weekend. It got better as I went lower as the snow report went from 7” on top to 9” at mid-mountain, and the snow became less tracked.
But I wanted UNTRACKED, so I headed over to the Twilight area. Because the egress from the Priest Creek area is on the Duster cat track, the runs get progressively less tracked the further towards High Noon you go. In here I found the goods as bouncy bottomless powder greeted my every turn. I did have to cross tracks, but that did not affect the quality of the turns.
I had considered going over toward Flying Z, but went back for more in Twilight. Even though the temperature had risen a few degrees to -6F, it wasn’t warm enough to convince me for another run and I headed down Heavenly Daze.
I had another 6” on my deck this morning, and it is snowing lightly. The tail end of the first part of the storm cycle is moving through our area, and snowfall will decrease by this evening after an additional 3-6” during the day. I was optimistic we would be getting near the upper range of my 14-28” forecast, but it appears we will be at the lower end. The mountain-top wind direction never really turned to the northwest for an extended period during the storm and snowfall rates were lighter than I originally anticipated.
A longwave trough extending through the western US and Canada will keep the bitterly cold temperatures in place for the next week. Periods of snow and reinforcing cold air surges will occur this entire period as energy moves down from the polar regions into this longwave trough.
One of these surges is currently timed for Friday but only very light snowfall is expected. Another series of waves moves over us this weekend continuing the cold and forcing higher snowfall rates. Even though there will not be a lot of moisture in this very cold air, snow densities of around 2-4% will create extremely light and fluffy snow leading to not insignficant accumulations.
A final trailing wave on Monday will likely bring the coldest temperatures of this arctic outbreak. Mountain slopes should begin warming by mid-week, though the valleys will remain locked in bone-chilling cold as inversions develop, strengthen and persist.
Tuesday, December 3, 2013
There was about an inch of snow on the hill by the time I made it up there this afternoon, and skiing on the north and northwestern aspects was soft. The left side of Storm Peak Face in the Sideburn area was excellent after which I tested the left side of Twister. A bit crunchy, so I traversed over to Tornado and skied soft snow to Tornado Lane.
Up for another ride and skied soft snow in the Ridge area down to Flying Z. Even the sides of the more trafficked runs Tornado Lane, Heavenly Daze and Vogue provided a soft mix of natural and man-made snow. About an inch of snow on my deck in these last 2 hours, and it is currently snowing. Looking forward to tomorrow!
Models are struggling with the exact timing of the moderate snowfall, but it still is forecast to arrive sometime this afternoon. The cold front just to our north gets pushed northward or held stationary by the southwesterly winds aloft until it regains forward progress, certainly by sunset today. Snow will become moderate to heavy then, and continue through Wednesday afternoon. I still expect accumulations likely exceeding 2 feet by sunset Wednesday on the hill, with significant accumulations in the valley as well.
Very cold air will accompany the decrease in snowfall late Wednesday as the main upper low moves overs us. Frigid Thursday temperatures will be reinforced by another wave of extremely cold air entering the area Friday. Another storm dropping south from the arctic will bring yet another wave of cold and significant snow by mid-weekend.
The cold and snow pattern looks to persist into early next week as the currently forecast last very cold wave moves overs us on Monday. This one is not as far west, and it appears that the storm cycle will end then as westerlies begin to infiltrate our area. However, the significant valley snowfall combined with low sun angle this time of year promises vigorous and long-lasting valley inversions, even as the mountain slopes begin to moderate by Wednesday or Thursday. Winter is here to stay!