Though natural avalanche activity will taper off tomorrow human triggered avalanche activity remains likely.
The storm brought a mix of rain and snow to higher elevations. As you transition into dry snow and wind-blown areas watch for cohesive storm slabs that are reactive to human triggering.
Storm snow and extreme southerly winds have built reactive storm slabs, especially on leeward terrain features where deposits are deep. As precipitation tapers off and freezing levels natural avalanche activity will taper off however storm slabs will likely still be reactive to human triggering.
As rain thoroughly saturates the snowpack surface snow will lose cohesion likely resulting in a loose wet avalanche problem on steep slopes.
A crust with weak, faceted snow above and below exists near the base of the snowpack. If triggered storm slab avalanches could step down step down to deeper layers resulting in very larger avalanches.
On Friday, explosives control resulted in numerous storm slab avalanches to size 2. A few natural storm slabs including a natural cornice-triggered storm slab to size 2 were also reported.
On Thursday, a skier accidental, size 1, storm slab avalanche was observed on Disease Ridge. Storm slab avalanches were reactive to explosives and human triggering up to size 1.5.
On Tuesday, a large storm slab avalanche was triggered by a skier on Metal Dome on an open east-facing slope at treeline. Another skier-accidental avalanche was reported to have failed within the storm snow near Oboe on a northwest slope.
Please continue to post your observations and photos to the Mountain Information Network. It helps strengthen our data gathering.
+40 cm of new snow and strong southerly winds have built deep storm slabs in lees. New snow overlies previous wind-affected surfaces in alpine and open treeline terrain. Below 1700 m precipitation fell as rain saturating the snowpack.
A thick widespread crust formed in late December is down 60 to 90 cm. In the alpine, it is thin and breakable. Professionals are concerned that small avalanches may run down to this crust and create larger-than-expected avalanches.
Near the base of the snowpack, a weak facet/crust layer from mid-November can be found and remains a concern for triggering with large loads or on thin spots. In general, the snowpack is shallow.
Friday Night
Periods of rain or snow continue, 10 to 15 mm. Winds will ease to southerly 40 km/h. Ridgetop low-temperature -1 C. Freezing levels will slowly fall to near 1500 m by Saturday morning.
Saturday
Cloudy with sunny periods and flurries easing by mid-morning, 5 mm. Southeast winds of 40 to 60 km/h. Ridgetop high-temperature -1 C. Freezing levels will be near 1500 m.
Sunday
Mainly cloudy with isolated flurries, 5 mm. Light variable winds gusting 20 km/h. Ridgetop high-temperature -1 C. Freezing levels 1500 m.
Overnight rain changes to snow, 10 mm. Freezing levels will fall to 1000 m by Monday morning.
Monday
Cloudy with sunny periods, with isolated flurries, 5 mm. Light variable winds gusting 20 km/h. Ridgetop high-temperature -3 C. Freezing levels 1000 m.
More details can be found in the Mountain Weather Forecast.
