Avalanche Forecast

Increasing clouds are expected for the northeast Cascades with very light snow potentially developing late in the afternoon. Further south only a general increase in high clouds should be seen for the central-east and southeast Washington Cascades. Milder temperatures in the alpine will continue Monday with temperature inversions for the lower slopes. Alpine winds out of the SW are forecast to ramp up Monday afternoon.  

Recent wind slabs should be found primarily on N-W-S aspects closer to the Cascade crest while recent loading patterns in the Mission Ridge area have transported snow onto more easterly aspects. Be aware of recent loading patterns in your area. The benign weather will continue to very slowly allow these layers to stabilize. Remember that firmer wind transported snow is always your best sign of wind slab layers.

Continue to identify the 12/17 buried PWL in snowpits and avoid areas where the overlying snowpack is shallower such that affecting this layer would be more likely.

Avalanche watch issued Monday night through Tuesday: A drastic change in the weather pattern to wetter and milder weather should substantially increase the avalanche danger on Tuesday.  

Moderate precipitation with a slow warming trend will likely affect the northeast Cascades beginning Monday night with moderate loading and warming continuing on Tuesday. We have higher confidence in High avalanche danger for the northeast zone including Washington Pass on Tuesday. 

For the central-east and southeast Cascades, precipitation amounts, type and timing are less certain and High avalanche danger may occur Tuesday or not until Tuesday night.  

An abundance of weak and cold snow in the upper snowpack combined with the potential for rapid warming and high precipitation rates would lead to very dangerous avalanche conditions during this period and backcountry travel is not recommended. Check the forecast Monday evening for updates. 

The 12/17 PWL and other persistent weak layers closer to the surface have been largely unreactive as of late. These layers may awaken during the expected upcoming warm and wet period with the potential to produce large and destructive avalanches. 

Weather and Snowpack

A pair of warm fronts moved across the Northwest last weekend which allowed some relatively milder Pacific air to finally work its way east of the crest Sunday evening and night. 3-8 inches of snow fell through Monday morning, 1/9 along the east slopes. 

A weak low pressure system, tracking across Oregon Tuesday morning through Wednesday afternoon produced 1-5 inches of snow in the central east to southeast Cascades with the most seen at the Lost Horse and Potato Hill Snotels in the southeast Cascade zone. E to NE winds increased Tuesday afternoon.

Snow showers deposited another 2-4 inches early Wednesday in the southeast Cascades zone, with little or no snow in the north and central.

An upper ridge over the northeast Pacific Ocean has caused fair weather Thursday through Sunday over the Cascades with mostly light winds and moderating temperatures seen mainly at higher elevations along the east slopes due to strong temperature inversions. Low clouds over Eastern Washington stayed banked up against the east slopes over the weekend while the mountains mostly enjoyed the sunshine. 

Surface hoar and near surface faceting has been noted widely throughout the range in sun and wind sheltered locations below treeline. Sun crusts have formed on steeper solar aspects over the last few days. The best riding and skiing conditions have generally been reported in less wind and sun affected areas below treeline during this stretch of fair weather.

Recent Observations

NWAC pro-observer Tom Curtis was on Mt Cashmere Wednesday and pulled the plug on continuing a tour due to the conditions observed. The sound of a natural avalanche rang out loudly in the valley Wednesday morning. It was estimated the slide released from a more westerly aspect near tree line. Other concerning observations included finding a reactive buried thin crust with faceted crystals below and a 25-35 cm 4F slab above. Cracks were shooting from skis and snowpit tests also indicated human triggered slab releases would be likely in this area.

The NCMG were at Washington Pass on Wednesday and reported that wind slab from last weekend was primarily seen on E-SE terrain features and was becoming less reactive.

A couple reports via the NWAC Observations page are available for Wednesday. A report from Mt Cashmere indicated a shallow, variable snowpack with evidence of wind loading from last week. A collapse and snowpack cracking was seen on a southeast slope at 5300 feet due to a facet/crust layer at 35 cm down but these layers were not found to be widespread. A skier also reported 14-16 inches of snow and snowpack collapsing on Manastash Ridge on Wednesday.

Tom Curtis was on Diamond Head at Blewett Pass on Thursday reported many wind scoured areas with previous wind transport primarily to W slopes. The 12/17 PWL was found at 30 cm down but was not reactive. Facets at the base of the snowpack were not giving test results.

Tom Curtis was out again on Friday on Mt Cashmere and on a W aspect near treeline and he found the 12/17 PWL at 55 cm giving a PST 37/100 End. He noted some previous wind transport and cross loading on N-W-S aspects. Tom also found great skiing conditions in the trees. 

An observation via the NWAC observation page from Saturday continued to identify weak persistent grains near the base of the relatively shallow snowpack in the Mission Ridge area. While these layers were reactive in column tests, no recent avalanche activity has been observed involving these layers.