Avalanche Forecast

Only very light new snow accumulations are expected through Tuesday afternoon. A clearing trend is likely for the northwest Cascades Tuesday with a mix of sun and clouds more likely for the south and central Cascades Tuesday afternoon. A cooling trend that begins Monday night will continue during the day Tuesday. 

Wind slab formed over the weekend and found mainly on northwest to southeast slopes near and above treeline continues to be the most likely avalanche problem along the west slopes. Specifically in the Mt. Baker area, be aware of a higher likelihood of triggering wind slab where it overlies recently buried surface hoar. Field observations suggest this setup exists in isolated areas on northerly aspects near treeline in the Mt. Baker backcountry. 

Weather and Snowpack

An atmospheric river arrived over the Northwest Tuesday 1/17 with highly variable weather seen throughout the Cascades during this event. Heavy rain was seen up to about 6000 feet or higher in the north Cascades and up to about 7000 feet or higher in the south with snow at higher elevations. Sleet and freezing rain Tuesday 1/17 at Stevens and Snoqualmie changed to snow at higher elevations on Wednesday 1/18.  At Stevens and Snoqualmie Pass the freezing rain crust is about 1 inch thick. 

A storm cycle from Thursday 1/19 through Sunday 1/22 deposited 1-2 feet of snow along the west slopes of the Cascades with the greatest totals seen at Mt. Baker.

A large upper ridge and warm air mass built over the Northwest Thursday to Saturday with temperatures reaching the 40s in many places along the west slopes away from the lower parts of Stevens and Snoqualmie. Strong southwest winds were seen Saturday in the Northwest Cascades, with moderate southwest winds in the central west Cascades and light winds in the southwest Cascades. East winds were seen at Stevens and Snoqualmie. Sun crusts formed on most solar aspects during this period. 

A weak front crossed the PNW Sunday afternoon and night, depositing 1-4 inches of snow with the most at Mt. Baker. A slight cooling trend under mostly cloudy skies followed on Monday.  

Recent Observations

North

NWAC received an observation Saturday evening describing 2 groups of skiers who triggered 3 separate wind slab avalanches with depths averaging about 2 feet in the Mt. Baker backcountry. The wind slab avalanches were triggered on N through E slopes between 5000-5800 feet on Mt Herman with one slide burying a skier waist deep. Fortunately the skier involved was not injured.

NWAC pro-observer Lee Lazzara was in the Bagley Lakes area on Saturday and reported wind slab formation. He also reported a large cornice failure on Saturday night onto a north slope of Table Mountain near Mt Baker at about 5000 feet. 

Lee was back out in the Mt. Baker backcountry Monday and through a fair number of column tests found wind slab reactive in isolated pockets near treeline where buried surface sat above the old snow surface from 1/28. Wind slab was found on a variety of aspects above treeline, but did not show signs of likely propagation. About 10-15 cm of new snow was not well bonded to the previous snow surface but too shallow to be a significant avalanche problem.  

Central

NWAC pro-observer Ian Nicholson was at Stevens Pass on Sunday and observed small loose wet activity in the morning before cloud cover and cooling quickly diminished the loose wet potential. A layer of small faceted crystals above the 1/17 crust are becoming rounded at about 40 cm down and were not reactive in column tests or on test slopes.

South

NWAC pro-observer Dallas Glass was at Paradise on Sunday and traveled up to about 6400 ft. He found a new surface melt-freeze crust from Saturday over about 15 inches of settled recent snow on the thick crust from 1/17 on solar aspects.  True northerly aspects still held some settled powder. During the day some wind transport was seen at higher elevations above treeline. Evidence of numerous small loose wet and size 1-2 wet slabs from Saturday were seen on solar slopes.