Register for an account and never miss a forecast again!
RegisterRegister for an account and never miss a forecast again!
RegisterFeb 18th, 2019–Feb 19th, 2019
Mt Hood.
An incoming storm should build fresh but shallow wind slabs by the end of the day. However, it's the potential for a low-likelihood - high consequence persistent slab avalanche that should continue to shape your travel choices, steering you away from slopes capable of producing large avalanches.
As recently as Monday, February 18th, Mt. Hood pro-patrol is finding the same weak snow (1-2 mm facets) over a hard crust on northerly aspects below treeline roughly 3 feet below the snow surface. What has changed is that we haven't had an avalanche release down to this depth, human or explosive triggered, in several days over the busy holiday weekend.
So the ingredients for a destructive persistent slab avalanche remain in place, but they have become harder to find and to trigger. When choosing how you travel through terrain, keep the odds in your favor by choosing simpler terrain at any elevation not capable of producing a large avalanche.
The new and significant round of snow and wind begins late Tuesday afternoon and continues through Wednesday will test this potentially dormant interface.
We are thrilled you are enjoying winter and traveling (safely) in the backcountry. Take a moment and submit an observation for the Mt. Hood area, especially for places less traveled.
February 15, 2019
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).
A natural persistent slab avalanche (D2.5) on a southeast aspect at 6,600ft. Grindstone Mtn in Icicle Canyon. Likely ran 2/12. Photo: Matt Primomo
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.
Large surface hoar near Snow Lake Divide on February 7, 2019 just before it was buried on the 8th. Photo: Jeremy Allyn