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RegisterJan 11th, 2020–Jan 12th, 2020
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Another winter storm will maintain dangerous avalanche conditions, especially in areas closer to the crest. A healthy amount of respect is warranted for steep slopes at upper elevations due to uncertainties with our quickly deepening snowpack. Plan to give yourself options to avoid steep slopes, as snowfall during the day will increase the danger of slab avalanches.
On Saturday, an observer found very reactive, shallow storm slabs in Icicle Creek. I found 8" of new snow without storm slab concerns on Table Mountain near Blewett Pass, though wind slabs were a concern in isolated locations near treeline. Mission Ridge reported a few wind slabs up to 10" deep with control work, where 4 inches of snow fell at their mid mountain site. Storm totals increase substantially closer to the crest. The Sasse Ridge Snotel site (4,300ft) has gained 22" of snow with 2" of water equivalent since the morning of the 10th. Expect increased danger due to more snow further west in the zone, and perhaps less in the eastern half. There have been isolated reports of a reactive layer of buried surface hoar in the zone, generally near and east of Blewett Pass. We have limited information about this layer, so it may be prudent to dig down to look for deeper weak layers such as these on Sunday.
Reactive, shallow storm slabs were found below treeline in Icicle Creek. January 11, 2020. Ryan Carrasco photo.
January 9th, 2020 (The regional synopsis is updated every Thursday @ 6 pm)
As we said Happy New Year and rang in 2020, snow was turning to rain at many trailheads and lower elevation Passes, not exactly the fresh start winter recreationalists had in mind. The snowpack was already looking a little thin throughout the region, especially at lower elevations. Low snow in places like Snoqualmie Pass made backcountry travel difficult and hazardous. NWAC’s snow depth climatology report was showing snow depths 25-64% of normal to kick off the start of 2020.
Things can change quickly in the Pacific Northwest and they did as we entered an extended storm cycle between January 2nd to January 8th. Strong winds, fluctuating temperatures, and heavy precipitation offered few breaks in the weather over this period limiting observations and hampering travel. Despite periods of rain at lower elevations, most areas saw several feet of new snow with big jumps in total snow depths as a westerly storm track strongly favored the West Slopes of the Cascades and the Olympics for the highest precipitation totals.
Location
Total Snow Depth (in) 1/2/20
Total Snow Depth (in) 1/8/20
Hurricane Ridge
31
51
Heather Meadows Mt Baker
55
95
Washington Pass
49
74
Stevens Pass
41
63
Snoqualmie Pass
22
33
Alpental mid-mountain
44
63
Crystal Mt Green Valley
40
66
Paradise Mt Rainier
54
105
White Pass Upper
43
69
Timberline
36
57
Mt Hood Meadows
36
53
We may have started with a shallow snowpack, but most locations increased their snowpack by 70% or more over this storm cycle!
During this extended and impressive storm cycle that included backcountry avalanche warnings, natural avalanches were reported in many areas Jan 6th-7th.
The Stevens Pass area was especially active over the period with over 100(!) avalanche observations made on the 6th and 7th. Professionals reported numerous avalanches in places that they hadn't previously observed avalanches and some paths avalanched multiple times in a 24 hour period. Observers reported a few very large (size D2.5-3) avalanches, originating at upper elevations with deeper crowns that likely formed from wind drifting. Topping off an active couple of days, warming temperatures lead to a widespread loose wet avalanche cycle.
The southern Washington Cascades, the Wentachee Mountains and Mt. Hood either saw less precipitation, warmer temperatures leading to more rain than snow, or some combination of the two and ended up with relatively less active avalanche conditions than areas further north.
A large natural avalanche on Rock Mountain near Berne along Hwy 2 east of Stevens Pass that released Jan 6th or 7th. Photo: Josh Hirshberg 1/7/20
Many small storm slabs released in the Crystal backcountry 1/6-1/7. Pinwheels in the photo suggest loose wet avalanche activity occurred when temperatures rose above freezing and snow turned to rain.
Another active and colder weather pattern is on it’s way. Enjoy yourself out there and be sure to check the forecast before heading out. Remember, NWAC is a community-supported avalanche center and when you submit an observation you make the forecast better!
-Peter Moore
It’s getting deeper! Photo: Jeremy Allyn