Avalanche Forecast

Southwest flow should carry an energetic front and shortwave to the Northwest Saturday evening and night. Moderate west flow should carry a 2nd short wave, an upper low and a cool unstable air mass to the Northwest Sunday. This should cause southwest to west winds, rain or snow changing to snow showers and lowering snow levels on Sunday. Snow and snow showers should cause up to about 6 inches of snow in the above treeline along the east slopes by the end of the daylight hours on Sunday.

A mix of likely dangerous winter and spring avalanche conditions is likely on Sunday especially nearer the crest in the above treeline . The sun is getting much stronger and new snow may be very reactive to solar effects. The greatest danger should be in the afternoon to the end of the daylight hours.

New wind slab is most likely on lee slopes in the above treeline on Sunday. This is most likely on north to east slopes but possible on other aspects. Watch cracking and firmer or chalky wind transported snow. Snow pits may not be helpful due to variability in the snowpack.

New storm slab layers will be likely in areas where there is rapidly accumulating snow for more than a few hours. Again this is mostly likely nearer the crest. Warming daytime temperatures may contribute to upside down layers and instability. Pay special attention to slope convexities where storm slab is mostly likely to be triggered.

Due to recent sensitive storm slab releases on a suspected spotty 3/12 buried surface hoar layer, we are currently listing it as a persistent slab. Though it may be spotty and not widespread it should nonetheless get attention from backcountry travelers in the NE zone.

Loose wet avalanches won't be listed due to other potential avalanche problems on Sunday but may be possible on steep solar slopes on Sunday especially nearer the crest. Don't overstay your welcome if you start seeing pinwheels or small initial natural loose wet avalanches. Be aware of terrain traps where even a small loose avalanche could have unintended consequences if you venture out on Sunday.

Cornices have grown large recently. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.

Weather and Snowpack

A spotty layer of surface hoar likely formed and was buried on about 3/12 mainly in the northeast Cascades with the terrain most suspect being N through E facing slopes.

Snow accumulations Wednesday to Friday following the last front varied based on proximity to the Cascade crest and higher terrain with about 12 inches at the NRCS Lyman Lake Snotel, 6 inches at Harts Pass and next to nothing at Blewett, Mission Ridge and Berne weather stations. Crest level westerly winds were strong and sustained at the Mission Ridge station through Thursday afternoon.

Frequent March storms have built large cornices along ridges in many areas.

No avalanches have been noted for quite some time on a persistent buried surface hoar layer from February 27th in the Washington Pass area and to a lesser extent the central-east zone. Avalanches releasing on or down to this layer are unlikely.   

Recent Observations

The last known human triggered avalanche on the 3/12 PWL in the Washington Pass area was on 3/19. 

The North Cascades Heli Skiing operation skied extensively on a non-solar slope in Cedar Creek on Monday 3/21 and did not observe any avalanche activity in nearby terrain.

On Wednesday 3/23 NWAC pro-observer Tom Curtis was in the Blewett Pass/Table Mountain area and found dust on a mostly supportive crust prior to the incoming frontal system. Also of note, many windward and solar slopes were nearly or completely melted out up to about 6000 feet. 

Mission Ridge pro-patrol reported strong west winds Thursday morning but little in the way of avalanche concerns in area due to the lack of new snow. On Saturday they reported minor small point release loose wet avalanches and minor rollerballs.