Avalanche Forecast

A very weak front should move through the high pressure ridge Sunday. Only very light amounts of precipitation are expected overnight Saturday and Sunday at initially high freezing levels but with a cooling trend. This weather should further allow for any unstable layers to bond and settle in place as warm dense surface snow helps to consolidate older weak snow from last week, causing an overall slowly decreasing danger. However, pay close attention to local conditions, especially if the area you are traveling in received more significant new snow. Watch for evidence of any wind transported snow at higher elevations where colder surface snow may be available to transport to lee slopes. 

The last significant snow fell over the first few days of December along. This storm produced heavy rains with a significant cooling trend that deposited 1-2 feet of low density snow over most sites in this region. Following this storm cycle, a strong and generally thick rain crust formed below the gradually lower density surface snow and also formed a relatively good bond to this crust. With the cooling profile and lack of significant wind, little avalanche activity occurred shortly after the storm.  

Dry and very cold weather followed with periods of both strong easterly ridge top winds a week ago, then strong west to northwesterly winds last Sunday and Monday. This transporting loose surface snow and built small and isolated wind slabs on a variety of lee slopes. and produced some isolated triggered soft slabs on higher steep lee terrain.  

The dry and cold stretch produced widespread and thick surface hoar growth, near surface faceted snow and began to break down the strong crust in some areas due to re-crystallization from strong temperature gradients within the upper snowpack.

On Thursday, several hours of very strong westerly winds hit the Cascade crest, especially as recorded by NWAC weather stations at the top of the Mt Baker ski area. This wind transported loose surface snow and did build pockets of wind slab that produced some ski triggered but relatively shallow slab releases, mainly at the Mt Baker area.

The surface snow conditions have all but changed as of this Saturday as a result of significant warming and a little light rain or heavy dense snow Thursday night and early Friday. Precipitation amounts remained light but some areas of unstable wind or storm slabs did produce ski triggered slabs Friday in the Mt Baker area ranging from 10-30 cm (4-12 in.) These shallow wind slabs were releasing on weak near surface faceted snow formed under the recent cold temperature regime.

Elsewhere, most areas only received about 2-5 inches of snow or light rain at mid and lower elevations by early Friday. Other than the Mt Baker area there have been few other reports of activity as of Saturday afternoon. Given a full day of warm temperatures, some previous light rain or heavy wet snow late Thursday, this will likely settle the previous low density snow making triggered releases much more difficult from any remaining shallow wind or storm slab layers.  These potential unstable layers may remain more sensitive on some steep shaded northeast facing terrain at the highest elevations, though remaining relatively shallow in most areas.