Avalanche Forecast

A low pressure system crossing Oregon Tuesday night will cause a sustained round of moderate easterly winds through Wednesday morning. Light snowfall should taper off in the morning for the southeast and central-east Washington Cascades with clearer conditions expected over the northeast Cascades. Winds will not be nearly as strong as the east wind event of last week, but there is low density snow available for transport and cold temperatures Wednesday will help preserve any new instabilities.

New wind slab should build through Wednesday morning due to easterly winds depositing snow primarily on lee westerly aspects. Transport winds will be more out of the northeast in the Washington Pass zone. However, also watch for cross-loaded slopes and lingering wind slab on a variety of aspects. Watch for firmer wind transported snow and avoid freshly loaded slopes in all elevation bands.  

Small loose dry avalanches are possible in steep wind sheltered terrain but will not be listed as an avalanche problem. 

Continue to identify the 12/17 and less deeply buried PWLs in snowpits and avoid areas where the overlying snowpack is shallower where affecting these layers would be more likely.

Weather and Snowpack

A cold and dry Arctic air mass was over the Northwest last week. The main weather event during this cold snap was a day of strong east winds last Wednesday that created widespread variable snow surfaces by scouring windward slopes and re-distributing the snow to a variety of aspects.

Reports indicate the winds eliminated most of the faceted surface snow and surface hoar that formed in the near and above treeline during the cold weather. But these weak surface crystals were still reported below treeline prior to snowfall that fell over the weekend.

A pair of warm fronts moving through the PNW Sunday and again Sunday night allowed some relatively milder Pacific air to finally work it's way east of the crest Sunday evening and night. 3-8 inches of snow fell through Monday morning along the east slopes. 

A weak low pressure system tracking across southern Washington Tuesday morning produced 1-5 inches of snow for the central to southeast Cascades with the most seen at the Lost Horse and Potato Hill Snotels in the southeast Cascade zone. East or Northeast winds were increasing Tuesday afternoon with another round of light snow developing over the southern Cascades. 

Recent Observations

On New Years Day reports from multiple snow pits by the the Mission Ridge pro-patrol indicated that basal facets remained intact but were showing signs of rounding and bonding. Mission Ridge experienced a whopper of a snow storm on Jan 2nd when unusual reverse orographic flow produced about 34 inches of new snow along with strong northeast winds. 

A report for Friday 1/6 via the NWAC Observations page for Red Mountain in the central east zone indicated a 10-20 cm deep surface layer of faceted surface snow and surface hoar in the below treeline band. A wind slab also gave a triggered collapse on a ridge top.

The Mission Ridge pro-patrol on Saturday reported that the deep low density heavy snow from early last week had greatly consolidated and stabilized.

The NCMG were out on Delancey Ridge on Saturday and found that snow from a week ago had settled and stabilized. Weak surface layers were noted with surface hoar in the below treeline. Small wind slab was noted in the near and above treeline which was not reactive.

The NCMG were in the Hairpin Valley Monday and observed a natural loose cycle that likely occurred Sunday night. While a couple of storm layers were identified in snowpack tests, the only other direct sign of instability was a small wind slab triggered by cornice fall that again likely occurred Sunday night.