Be on the lookout for wind slabs in steep unsupported terrain. Strong easterly winds on Saturday afternoon loaded leeward slopes in the Alpine. Surface conditions at upper elevations yesterday varied from wind skin to rime crust to sastrugi to wind slab. Winds are forecast to increase again today and there is still snow available for transport. Look for stiff, pillowed snow and cracking and listen for hollow, drum-like sounds. Loading patterns can be very localized and it is crucial to look for clues indicating where the snow is being distributed.
Sunburst weather station wind profile from Friday afternoon to Tuesday morning
Surface conditions on Sunburst and cross-loading on the north side of Magnum, December 3, 2018. Photo: Heather Thamm
In the Alpine, sitting anywhere from 1 to 3′ below the snow surface, is a thin layer of weak snow (buried surface hoar/BSH). It got a good shake on Friday during the earthquake and a number of quake triggered avalanches are thought to have run on this BSH (buried November 23rd) layer. Did that shake it up enough??? That is the hard to answer question. An observer Sunday found this layer to still be reactive in a snowpit on Sunburst right around 2500′. Yesterday at 3100′ on Sunburst there were no results testing this layer but it was very easy to spot laid over in the snowpack. The concern is finding a slope with buried surface hoar that is still intact, reactive and that propagates into an avalanche. At this point obvious signs of instability may not be observed but some lingering suspicion is advised even as the likelihood decreases. As always use safe travel protocol and choose terrain with consequences in mind i.e. where is the avalanche path and where would I end up if the slope slides?
Yesterday: Skies were partly sunny with temperatures in the low 30Fs to mid 20Fs. Winds were easterly 5-15 mph with gusts in the 30s. Overnight temperatures dropped into the mid 20Fs to high teens.
Today: The forecast is for mostly cloudy skies with a chance of rain/snow showers with rain/snow line around 800′. Temperatures will be in the mid 30Fs to mid 20Fs depending on elevation. Winds are forecast to be easterly 20-40 mph with gusts into the 50s.
Tomorrow: Cloudy skies and rain/snow showers are forecast to continue. Winds should decrease and temperatures will be slightly warmer. The National Weather Service long term discussion had a couple of interesting quotes this morning, “A high degree of uncertainty will make for an interesting forecast for the end of the week and into early next week. In short it looks like an active and wet period, but the details are murky due to model disagreement and inconsistency being far below normal.”
*Seattle Ridge wind sensor is rimed over. Alyeska Mid Wx Station and Summit Lake Snotel snow depth sensor are not functioning.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||27||0||0||13|
|Summit Lake (1400′)||17||0||0||*no data|
|Alyeska Mid (1700′)||28||0||0||*no data|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||*no data||*no data||*no data|