Haines Avalanche Center

Forecast as of 2018-12-20 at 09:00 am and expires on 2018-12-20

Above 2,500ftHigh

1,500 to 2,500ftHigh

Below 1,500ftNone

Degrees of Avalanche Danger

Avalanche Problems

Problem Details

Problem #1: Storm Snow

Location: All aspects and elevations. Slopes 27 degrees and steeper. Storm totals are between 26-52" so far (highest amounts in the Transitional Zone), and around 2" additional is likely through the next 24-hours. Winds have increased out of the southeast, causing active wind loading on North through West aspects, and cross loading on NE and E facing terrain features. Anywhere the new snow is wind loaded it will be slabby and prone to natural and human triggering. These storm slabs may be 30-120cm thick. Steep terrain will be actively flushing new snow through gullies. Avoid all terrain steeper than 30 degrees until this new snow has some time to settle. If you venture on to steeper slopes, watch carefully for any slabbyness or wind effect that could cause propagation across a slope. Carefully avoid convexities and any terrain traps. 

Problem #2: Persistent Slab

Location: All wind-sheltered slopes. Areas of surface hoar formed around Dec.1st, and again on the 14th, mainly on wind-sheltered slopes (including sheltered high alpine bowls). These patchy but dangerous weak layers may be lurking between 60-130cm deep, depending on wind loading and exposure. The exact distribution of this dangerous weak layer is unkown, and the only way to find it will be to dig a shallow pit and shear off the new snow to carefully look for flat, shiny hoar crystals. That said, one snow pit may not be representative of a whole slope. Surface hoar layers are notoriously tricky to map out. It would be best to assume this layer exists on sheltered terrain (especially near treeline) and to assume it will be easy to trigger an avalanche on this layer. This is not a good time to be riding large or complex terrain. Wait until we have more data about this layer's distribution. Surface hoar layers do not bond over time, and must instead be crushed or flushed out by a major storm cycle. Use extra caution out there and please send in any observations.

Avalanche Activity

There was a human-triggered D2 avalanche on White Pass Dec 16th, with remote triggering and a crown depth of 3-4ft,  on a wind-loaded northeast aspect at 1500m. One person was caught and buried to their waist/chest. 

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Sporadic natural storm slab avalanches were observed from the last week, size D2-D3 on wind loaded lee aspects and gullies (above 3000ft). Crowns were around 60-90cm thick.

Weather

An additional 2-4" of snow is likely through Friday, with snow levels remaining at sea level. Clouds and some light snow should linger through Saturday before clearing and cooler weather with increasing north winds begins Sunday, lasting for several days. 

   Snow Depth [in] Last 24-hr Snow/SWE [in] Last 4-days Snow/SWE [in]  Today's Freezing Level [ft]  Today's Winds Next 24-hr Snow/SWE
Mount Ripinsky @ treeline
   52" 8" / 0.7  43" / 3.80 0 light, var 2" / 0.15 *
Flower Mountain @ treeline
   65" 11" / 0.90 52" / 4.40 0 light, var 2" / 0.15 *
Chilkat Pass @ 3,100ft
   40" 4" / 0.30 26" / 2.20 0 light, var 2" / 0.15 *

( *star means meteorological estimate )

Additional Information

If you get out riding, please send in an observation!

Start the season with fresh batteries in your beacon, and do a rescue practice with your partners. Always carry a beacon, shovel, and probe, and KNOW HOW TO USE THEM.

Practice good risk management, which means only expose one person at a time to slopes 30 degrees and steeper, make group communication and unanimous decision making a priority, and choose your terrain wisely: eliminating unnecessary exposure and planning out your safe zones and escape routes.