Sunday, January 26, 2014
The uncertainty displayed in the numerical model guidance this past week is resolving itself as Pacific energy is forecast to undercut the persistent west coast ridge. This is the first time this season the polar jet stream is finally forecast to carry seasonably warm and very moist air into the west coast, bringing snow to the drought-plagued ski resorts located there and bringing a Pacific storm track into the Great Basin and Rockies.
Before this new regime takes hold, a weak but cold storm currently to our north will bring clouds to the area later today and light snow beginning around midnight. The westward extent of this storm is still bouncing around in the models, but I would expect snow all day on the hill tomorrow with 1-2” by Monday morning and possibly 3-6” by Tuesday morning, with most of that occurring by midnight Monday.
A break on Tuesday before the undercutting jet stream slams into the northwestern coast by late Tuesday. Similar to tonight, another cold wave drops down the west side of the Hudson Bay vortex and phases with a wave in the undercutting polar jet stream that is forecast to contain a fair bit of subtropical moisture. The end result is the polar jet stream is pushed southward to California and our flow backs from the north to the west, warming temperatures and increasing winds.
Snow is currently forecast to begin on Wednesday, and the interaction of the polar jet stream with the cold waves rotating around the Hudson Bay vortex will keep our weather snowy through the week. Additionally, the polar jet stream is forecast to buckle by the weekend, dropping a storm into southern California by the weekend and backing our flow further to the southwest. Snows are likely to continue through the weekend as this very dynamic weather pattern evolves.
With so many interacting pieces, predicting snow amounts is difficult at this time, but an extended period of moderate to heavy snows with periods of high winds is likely starting Wednesday and lasting through the weekend.
Friday, January 24, 2014
The hemispheric circulation pattern is changing next week, but the details are still uncertain. One source of uncertainty is coming from the much hyped polar vortex as it currently has split into two pieces. One vortex resides over the Hudson Bay as it has for much of this winter and last summer, while another vortex has settled over Siberia. The cross-polar flow between these airmasses is decreasing, and they are forecast to become isolated from one another by next week. However, the cross-polar flow is expected to increase near the end of next weekend, and the strength and location of this flow determines how much cold air flows from Siberia into Canada and vice versa.
Additionally, the west coast ridge has also been a dominant and long-lasting feature this winter, and models forecast major changes as Pacific energy is predicted to undercut the ridge. Furthermore, phasing of the undercutting energy with the cross-polar flow around next weekend will keep the west coast ridge evolving and uncertainty high in the medium to long range.
In the shorter term, mountain slopes will warm and valley will stay cool as inversions persist through the weekend. There is a dry grazing wave Friday night, but that won’t have much, if any impact on our weather. A far more substantial lobe of cold air rotating around the Hudson Bay vortex may begin dropping temperatures late Sunday, with light snow possible for Monday and Tuesday.
Forecast uncertainty then increases as another cold wave is forecast to drop down from the north and phase with Pacific energy undercutting the west coast ridge midweek. I’d like to emphasize the timing of the Pacific energy undercutting the west coast ridge is uncertain since the feature has been so dominant this entire winter, but it seems likely to happen. Furthermore, there are additional waves of energy forecast to rotate down from the north through Thursday, and if the west coast ridge undercutting eventually happens as predicted, we should remain in cool and moist northwest flow with accumulating snows, likely significant, through much of the week.
A major wave is then forecast to move through this undercutting flow around next weekend and will likely keep snows going. But the forecast for then will evolve as there is so much uncertainty midweek.
Tuesday, January 21, 2014
Another beautiful bluebird day lured me out for my afternoon ski. The visitors for the Martin Luther King holiday weekend have left, leaving a mostly empty mountain. The first run on Shadows threw me around a little as the snow covering the terrain features was stiff and unforgiving. I opted for a cruiser below Duster and into Moonlight, which was very carevable. Then, up Sundown to ski the left side of Westside, which always has soft snow at the end of the day.
Up Sundown again and over to Typhoon to find pockets of soft snow, which continued in the recently thinned trees on Drop Out. The final run up top was upper Closet to Twister, which was firmer than I would have liked. The southern aspects of the trail near the bottom were beginning to soften from the sun, but it did not last long before the trail tilted away from south.
Why Not trees also had stiff tracked powder on the lower mountain, and the left side of Vertigo was a bit softer than most of the turns today. The longer range models do have a pattern change advertised starting in about a week, but details are evolving.
Sunday, January 19, 2014
Beautiful sunny and dry weather will persist through Wednesday as a large and stable west coast ridge dominates our weather, though a grazing wave in northwest flow will knock temperatures back a bit on Monday. A small Pacific storm will interact with the ridge early in the workweek and the result of that interaction as well as the effects of another impulse dropping down the east side of the west coast ridge from the north will determine our weather for Thursday.
I don’t expect much precipitation from this scenario as the strong west coast ridge minimizes impacts from the Pacific storm. Cooler temperatures and perhaps only light snow with minimal accumulations are expected on Thursday before current forecasts cut off this storm from the mean flow and leave it over California to our south and west.
There has been and continues to be a large amount of uncertainty in the forecast for next weekend and beyond. It appears that all models want to change the hemispheric pattern and either undercut or break down the west coast ridge. Numerical models often struggle with pattern changes like this, and the uncertainty with next weeks forecast has persisted longer than normal. At this point, there is no use guessing what our weather may be until more stability emerges in the solutions not only between models but also within models.
Friday, January 17, 2014
The last new snow that fell was during the day Tuesday, but temperatures in the single digits during the night and twenties during the day have kept the snowpack in peak condition. I was up on Wednesday for the leftovers, which were great, but I brought my narrower boards today since I figured the snow would lend itself to a carve-ier ski.
First run, as usual, was down the upper part of Closet and then a traverse into Shadows. Closet was great with the snow soft and grippy, and there were even patches of unskied powder that was still soft and deep. The sun was starting to make the the snow thicker and heavier in Shadows, so I retreated back to skier’s right to find terrain with less of a southern aspect. The low sun angle this time of year really helps to preserve snow quality. so most things tilted west of due south remain very good.
Then into Lower Shadows where the ridgeline on skier’s left also skied great, especially if you can plan to turn where other’s haven’t!. Next run was a ripper down the Sundown lifline which skied soft and consistent. Short, medium or long radius turns - it didn’t matter as the snow allowed you to ski however you wanted.
Next run was in the 3:30 trees, but I found this to boarded out - by which I mean that several snowboarders have evidently turned in similar places making huge ruts in tight trees that made the skiing inconsistent. So I ambled over the 3 O’Clock and found the right side just off the grooming track to hold more great carveable snow. I then took Duster for another run down Lower Shadows, but noticed Patrol had dropped the rope on the left side of Lower Shadows recently, maybe even today. There were several very steep but short southern aspect lines that held very consistent but deep, heavy untracked powder. I traversed to the right to regain the ridge and the colder snow before getting dumped back into the lifline.
Last run up top was upper Closet and over to Typhoon. Lots of soft snow, and even some untracked in the tighter lines, and that skied great. Then, a couple of runs over in the Why Not trees that skied as well as anything up top.
It looks like we are in a dry spell for at least the next week, and models are struggling mightily with a pattern change advertised for around next weekend, so get the snow now while its at its freshest.