We have another snowstorm on deck for Friday/Saturday. The bullseye once again will be the Northern Rockies, including Big Sky in SW Montana and Jackson Hole/Grand Targhee in NW Wyoming. Idaho, Nevada, Utah, and California will likely see some flakes too. The storm will be packing some pretty cold temperatures with it too, allowing for lower snow levels than the last storm we posted about. The activity should continue next week with more chances for snow, but the models aren't quite in agreement yet.
Keys to the Chase
The action will begin tonight in both Idaho and Nevada. The Ruby mountains in Eastern Nevada will see a quick 3-7\" through Friday morning. Southern/Central Idaho will see similar totals during this time, with perhaps up to 10\" in the highest elevations of the Lost River Range. Sun Valley may see its first flakes up high. The Southern Sierra should see some flakes and light accumulations as well. We expect Mammoth Mountain to see their first flakes, if they haven't already. The action will quickly move into SW Montana and Wyoming, and Utah as well. It's still hard to say whether Big Sky or Jackson Hole/Grand Targhee will get the most snow out of this event, but both should do well, with 5-10\" possible. The Beartooths and Beartooth Basin will once again do well also. The higher end of that range will be possible in the higher peaks of the Tetons, not at the resort. The Beartooths and Beartooth Basin will once again do well also. The Northern Wasatch will see snow once again, with a few inches possible in BCC/LCC. Snow levels will range from 7000-8000 feet over most of the area. Check out the snow map below:
(image courtesy of Weatherbell)
While not an exact forecast, it shows the distribution of the snow pretty well, and the general areas where the heaviest snow will fall.
Details for the Weathernerds
Once again we'll have a trough passing through the Western US, bringing with it some cold temps and snow. See the gif below for the trough moving over the region.
(image courtesy of Tropical Tidbits)
You can actually see a second trough moving into the region beginning on Sunday as well. This will provide another opportunity for snow as well. Based on the position of the trough, the Northern Rockies will be in the best position for strong precipitation. Here is a shot of the 850mg (~5k feet) temperature departure from normal for the 5 day period ending September 25th. You can see the temperatures will be considerably below normal.
(image courtesy of Weatherbell)
The combination of the trough, the cold temperatures, and the lift shown in the 700mb vorticity map below will provide the ingredients necessary for some decent early season snow.
(image courtesy of Tropical Tidbits)
The circled area has some higher vorticity values, indicating stronger lift, and this roughly corresponds to the Ruby Mountains, Tetons, and SW Montana mountains, where the heaviest totals are expected. One final graphic to view this evening, the time height for Jackson Hole.
(image courtesy of the University of Utah)
These graphics are really cool, and we're glad the University of Utah provides them. They are read from right to left, and one of the key features to look at are the winds at different elevations, indicated by the wind barbs and the decreasing pressure (increasing altitude) on the y-axis. The blue line shows the freezing level and the greens show the relative humidity. In this run of the NAM model, you can see the temperature dropping starting tomorrow night and continuing through Friday evening. With the freezing level around 750mb, which is roughly 8k feet. The snow level is typically 500-1000 feet lower than the freezing level, so we wouldn't be surprised if the snow level lowered to 7k feet in the Tetons. At the same time, the relative humidity is increasing, going over 90% during the period, indicating there is considerable moisture in the atmosphere at lower levels. The winds aren't too strong, but there is a period of SW/WSW winds followed by W/NW, which should allow both Jackson Hole and Grand Targhee to benefit from some orographic enhancement.
Well, that's it for this evening. Enjoy another September snow!!
(photo by Joshua Esquivel)
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