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RegisterFeb 14th, 2019–Feb 15th, 2019
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If you venture into the backcountry, be certain of your ability to avoid avalanche terrain. New snow falling at warmer temperatures will stress our complex snowpack and create avalanches on Friday. Avoid steep slopes and put plenty of space between where you travel and large avalanche paths.
The Mt. Baker area received just over 30in of snow (2.20in SWE) since Monday. The snowpack will be stressed further with another foot of snow possible (.75-1in SWE) and warmer temperatures (2000ft snow levels) expected over the next 24 hours. Friday is not the day to travel in avalanche terrain.
Several natural and triggered avalanches have been reported this week throughout the Hwy 542 and Hwy 20 corridors. Avalanches have failed within new snow on multiple storm layers on all aspects at all elevations. These avalanches broke 1-2ft deep and up to 50-75ft wide. Avalanches have also occurred on a weak layer of old snow buried on February 8th. These avalanches broke up to 3 deep and over 100ft wide. Some of these persistent slab avalanches were triggered remotely. These avalanches have occurred near and above treeline on all aspects with the majority of avalanche activity on southerly slopes.
We have received a lot of snow over the past few days. These are the conditions when tree well and snow immersion suffocation accidents occur. Don't travel alone, and keep eyes on your partners. Check out https://www.deepsnowsafety.org/ for more information.
A natural persistent slab (D2) on a north aspect at 4200ft low in Glacier Creek drainage (Hwy 542). 02/13/19 Lee Lazzara Photo
Since February 8th, the mountains (and low elevation cities) of the Pacific Northwest have experienced cold and very stormy weather. Significant snowfall has added up in all forecast zones. Records from Snoqualmie Pass DOT avalanche workers back to 1973 show that February 11-12th set a record for the most snow recorded in a 24hr period at that location. The table below shows storm totals starting February 8th through the morning of the 13th
5 day totals ending morning of Feb 13th
Water Equivalent (inches)
24hr storm totals
(inches)
Difference in Height of Snow (inches)
Hurricane Ridge
1.97
N/A
+ 30
Mt. Baker
1.94
44
Washington Pass
1.66
NA
+ 16
Stevens Pass
2.71
49
Snoqualmie Pass
3.91
80
Mission Ridge
1.86
38
Crystal
2.91
59
Paradise
4.55
N/A
White Pass
N/A
57 (4400ft)
+ 26 (5800ft)
Mt. Hood Meadows
4.70
43
Heavy precipitation brought many mountain regions to their tipping point. Avalanches ran readily with a peak of snowfall intensity. For Stevens Pass, Snoqualmie Pass, East Central, West South, Mt Hood, and possibly West Central zones we have good confirmation that this cycle happened from the night of February 11th through the 12th. In other zones, snow totals haven’t been significant enough for widespread avalanche cycles, or we lack data (like in the East South zone).
The high rates of precipitation drove avalanches in the storm snow. Notably, a persistent weak layer of facets and surface hoar was buried in most zones on February 8th. Storms produced a widespread and prolonged cycle of avalanches on the February 8th interface, involving a variety of aspects and elevations. Local ski patrols, highway workers, and backcountry travelers reported extensive avalanching with widely propagating crowns and very sensitive conditions. With less stormy weather, observers have just begun to get a sense of the extent of the avalanche activity. Triggering persistent slab avalanches will be a concern for backcountry travelers in zones where the February 8th weak layer is active for at least the near, if not distant future. Stay tuned for more updates.