Avalanche Forecast

A somewhat unstable southerly flow pattern will maintain the possibility of showers Friday, especially during the afternoon. Most areas should only receive light showers, with possibly greater showers hitting the volcanic peaks. Freezing levels will gradually lower Friday but much of the shower activity should be rain below about 7000 feet.

The cooling will have the effect of solidifying the moist to wet upper snow layers, leading to a decreased danger of wet snow avalanches. However, any additional water from showers will maintain some wet snow conditions. All in all, there should not be enough new snow in the above treeline band to cause much new snow instability, nor should there be enough rain in the mid and lower elevations to cause too significant of increase there. The fact the upper snowpack is now fairly well drained as a result of the extended warm weather, it should be able to quickly drain the water received from showers, minimizing the threat of larger wet snow avalanches. 

Small loose-wet avalanches should remain possible Friday on steeper slopes. Watch for wet surface snow getting deeper than your boot tops, mainly where shower activity is heaviest. Triggered loose wet avalanches should be most likely on steep solar slopes, but could be seen on any steep aspect in this mild showery pattern. Watch for terrain traps that might funnel even shallow, loose snow, such as gullies and creeks. 

The potential for cornice releases will likely diminish, but still remain a possibility through the weekend. Cornice releases are very unpredictable, so avoid areas below cornices and remember that cornices can break much further back than expected along ridges.

Although not listed as an avalanche problem, powerful glide avalanches can release unexpectedly so also avoid areas below steep unsupported slopes or rock faces, especially if they are showing glide cracks.

Weather and Snowpack

In a word, HOT! Well, maybe two, Hot & Melting.

Freezing levels have been near or well over 10,000 feet for the past five days with strong spring sunshine. This is the third period in April with freezing levels above 10,000 feet and that has helped establish good melt water draining in the snowpack with much of the lower elevation snow continuing to melt away, transitioning to a spring snowpack. The last snowfall of 4-11 inches is now a thing of the distant past, having fallen late last week and assimilated into the upper melting surface layers.

Storms in March built unusually large cornices along many ridges. While these have been melting back, many have also failed recently, producing wet snow avalanches on slopes below during this recent warm weather. Cornices should remain a main concern over the near future. The potential for low probability/high consequence encounters, such as cornice failures and glide avalanches from steep unsupported slopes and smooth rock faces, should continue this spring. 

The mid and lower snowpack should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

WSDOT avalanche professionals working in the Chinook Pass area this week have, as expected under this hot weather, produced numerous small to moderate sized loose-wet avalanches. The upper layers of the snowpack appear to be draining well and with daily melt-freeze cycles, avalanches have mainly involved the upper surface layers of snow up to about the top 6 inches. There were several natural cornice releases noted Tuesday and Wednesday, each producing wet slides on the slopes below. 

NWAC observer Lee Lazzara covered a great deal of terrain in the Mt Baker backcountry earlier this week and noted similar conditions with all avalanche problems being heat related. Those being cornices, glide avalanches on unsupported terrain features and small loose-wet avalanches during the warm part of the day. The snowpack is quickly melting back in much of the terrain below treeline, making travel choices difficult for some lower elevation areas. ?