Northern Gallatin

On our way up Mt. Ellis, we noted widespread surface hoar on east facing slopes above ~7000', especially in open areas. Grain sizes ranged from 1 mm to 3+ mm at higher elevations. Winds were calm almost all day, even while on the skin track along the ridgeline. Given another 1-2 days of clear, calm conditions in the weather forecast, these surface grains could certainly continue to grow in size before the next storm.

We dug a pit on a south facing slope just below the Mt. Ellis summit. The snowpack on this solar aspect (77 cm) and not quite as deep as on easterly aspects. Although we found some basal facets in our pit, the bottom layer was stronger than we expected. We did not get propagating results on any layer with our ECT. Afterwards, skiing conditions on eastern slopes were excellent.

Yesterday afternoon, 1/14, saw lots of roller balls and a few sizable sluffs come down around the dribbles area. This morning lots of small sluffs coming down around bingo cave as soon as the sun hit it. Noticeably heavy, wet snow on solar slopes as well.

We rode into Portal Creek to the ridgeline above Hidden Lakes and back below Windy Pass. During our ride, we noted no avalanche activity or signs of instability. We dug twice to the ground. Once above Hidden Lakes and once in the corner of an avalanche path below Windy Pass. 

Bottom Line: 

• The snowpack is DEEP. The measured HS was "1 Dave" or 6'5" (200 cm).
• Stability is looking good in our pits, and we are optimistic. 
• ECTNs-mid teens within the layers of the post-Christmas storm snow. 
• Faceted snow near the base of the snowpack is hardening and rounding. Even with extra prodding (deep taps and an unofficial cross-slope PST), we couldn't get it to break or propagate failure.
• The mountain range is expansive, and one must assume spatial variability on both slope and certainly the range scale, but this is good. 

Big Picture: 

• Other than one avalanche that appeared to break on persistent weak layers below Maid of the Mist, Ian and I couldn't think of another persistent slab avalanche in the Northern Gallatin Range. 
• Wind Slab avalanches are the most likely issue.
• Danger is dropping quickly. 
• We don't trust facets often and aren't ready to write off the basal weakness, but triggering an avalanche on these layers seems unlikely for now. 
• This puts wind slab avalanches as the primary concern... and it hasn't been very windy. So, this seems limited for now. 

Terrain Recommendations:

• It is appropriate to consider riding and skiing in avalanche terrain if one is willing to accept the inherent levels of uncertainty involved with steep, backcountry terrain.
• We are pessimistic by nature and like to hedge our bets. The way to do this is by selecting terrain less likely to avalanche (not as steep, more uniform in depth—less rocky, potentially shallow areas, and not wind-loaded) and terrain with lesser consequences (smaller slopes, fewer terrain traps, clean runouts). 

Skied the third meadow and dug a pit this morning. Calm winds with no evidence of previous winds around 8500'. S1 in the morning which ceased as skies began to clear midday. No signs of instability were observed.

Our pit provided several ECT results on multiple interfaces, which we were curious about after this previous storm cycle but were surprised by the lack of propagation/quality in our results.

Probably already reported...but touchy storm slabs on Mt Blackmore. Attached is a photo of a natural from the approach, at the switchbacks to the upper basin.

Photo: Anonymous