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Advisory for Jan. 30

THIS Avalanche Advisory EXPIRED ON Jan 30, 2020 at 8:28 pm
Avalanche Advisory published on Jan 29, 2020 at 8:28 pm
Issued by Aaron Hartz
Bottom Line
We are expecting an increase in the daytime high temperature on Thursday and this could bring on the wet avalanche problems. Triggering a windslab avalanche is still a concern.
Avalanche Character 1: Wind Slab
Windslabs can be found near treeline and above treeline primarily on northerly and east aspects. They will not be everywhere throughout the terrain; watch for evidence of wind transported snow on lee slopes below ridgetops and around features that catch wind blown snow. Triggering a windslab will be possible in the right terrain with avalanches size D1-D2. If you see cracking in wind transported snow, this is a sign that windslabs are likely to trigger.
Avalanche Character 2: Loose Wet
This will be a timing issue. As the day warms up above freezing, monitor how the upper snowpack is looking and feeling. If the surface snow is becoming wet and mushy, avoid steep and committing slopes, especially with exposure to terrain traps. Triggering a loose wet avalanches will be likely near treeline and below treeline on all aspects. These avalanches will mostly be small (D1) but could be larger in big terrain. If melting and water penetrate into some of the recent layer boundaries, this could turn into the wet slab problem and become more destructive.
Avalanche Character 3: Cornice
With the warming on Thursday, cornices will weaken and become more likely to break. Cornices have been found on ridge tops mostly on north and east aspects near and above treeline. Remember, cornice failures can also trigger an avalanche on the slope below. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive.
Snowpack Discussion
The upper and mid pack are generally showing good structure and are right side up. We have no new observations from the deep pack
The 1/18 rain crust is now 50 to 80 cm below the surface. Storm snow from the last few days added 30 cm or more to the snowpack.
Recent Observations
A skier triggered slab avalanche on a north aspect at Paulina Peak was reported; (type not reported, likely a size D2). I recommend reading the report from Paulina. On Tuesday, multiple size D1 windslabs were triggered on ski cuts at Tam Rim (NW through NW aspects, near treeline). A report of cornice break(s) at the top of the Tuamlo bowl on Wednesday (easterly aspect, near treeline).
Mountain Weather
On Thursday the daytime high temperature is expected to break into the mid to upper 30's Fahrenheit. Look forward to some rain in the afternoon on Thursday. Wind is expected to be light (1-17mph) and primarily out of the south through west.

This snowpack summary applies only to backcountry areas. Click here for a map of the area. This snowpack summary describes general avalanche conditions and local variations always occur. This snowpack summary expires in 48 hours unless otherwise noted.

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