Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Apr 5th, 2015–Apr 6th, 2015

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

.

Due to a fair amount of uncertainty with the weather forecast, a moderate hazard rating will be maintained near and above treeline across the Cascades for new storm snow problems.

Detailed Forecast

An upper level weather disturbance should bring generally light to locally moderate new snow Sunday night through the first half of Monday followed by scattered afternoon/evening showers. Due to a fair amount of uncertainty with the weather forecast, a moderate hazard rating will be maintained near and above treeline across the Cascades for new storm snow problems. In areas that receive little new snowfall through Monday afternoon... expect a lower avalanche danger than the regional forecast. 

Shallow storm slabs may develop Monday with new snow bonding poorly to aspects with surface crusts. It's April, so be aware of increased solar input reaching more aspects and affecting the snow surface more quickly than winter-time. Loose wet avalanches involving recent storm snow will be possible as well Monday, especially if there are sunbreaks in the afternoon. 

Small loose dry avalanches are also possible on non-solar aspects at higher elevations. Loose dry avalanches won't be listed as a top avalanche problem, but be aware of fast moving sluffs knocking you off your feet and into unintended terrain traps on steeper slopes. 

Due to the continued cool weather, cornices won't be listed as an avalanche problem either but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.

Snowpack Discussion

Periods of active weather and mountain snowfall have finally graced the PNW since about mid March onward, and led to a few natural avalanche cycles. The largest avalanche cycle during this time period was observed in the Mt Rainier area March 25th and mainly above treeline due to rapid warming following heavy snowfall.

A front moved across the Northwest Tuesday followed by showers and rapid cooling. Storm snow from this system ranged from about 3-10 inches along the west slopes except at Snoqualmie Pass where 15-20 inches fell Tuesday night. A small natural cycle occurred at Alpental likely during heavy loading early Wednesday, but overall the new snow came with little avalanche activity. A front on Friday night brought another 1-4 inches across the west slopes. 

The average freezing levels for April have taken a major dive compared to much of this winter, averaging between 3-4000 ft since April 1st. This has helped feed the backcountry reports from across the Cascades near and above treeline of cool, preserved snow on non-solar aspects with limited wind effects, along with gradual storm snow settlement and generally a good bond to the previous crust.  On solar aspects, sun breaks even during low freezing levels have caused generally small loose wet avalanches. Sun crusts may now be found on solar aspects.  

Snowpack problems west of the crest should remain in the upper or surface layers. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this season. Many areas at the low elevations do not have enough snow to cause an avalanche danger.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.