Avalanche Forecast
Regions: Mt Hood.
Check the forecast for a mixed bag of spring avalanche problems and evaluate snow and terrain carefully on Saturday.
Detailed Forecast
Increasing mid and high clouds should be seen on Saturday. The best chance of some light rain or snow showers should be over the Olympics. Any rain and snow amounts will be light and should not cause a change in snow conditions. East winds should decrease over the Cascade crest and in the Cascade passes on Saturday.
The avalanche forecast won't change much from Friday.
Loose wet avalanches may still be possible on steeper solar aspects on Saturday. Loose wet avalanches may start small but could have the ability to entrain recent moist snow in mainly on steep solar terrain. High clouds Friday night may limit a refreeze of surface snow by Saturday morning.
Storm winds 3/13-15 likely built wind slab on lee aspects in the upper elevations of the above treeline band. This wind slab will mostly likely be found on NW-SE facing slopes. But east winds the past couple days will also have built wind slab on northwest to southwest aspects in places along the Cascade crest and in the Cascade passes. Hence the the wind slab avalanche problem will be indicated on all aspects in the near and above treeline.
Wind slab may also be locally possible in the below treeline on west slopes in areas that had east winds the past couple days. Firm wind transported snow and snowpack cracking can be good signs of wind slab layers.
Recently formed cornices have grown large and can become sensitive when it is warm and sunny. Avoid areas on ridges or summits where there may be a cornice and avoid slopes below cornices in the spring.
Although it won't be listed as an avalanche problem avoid areas below steep slopes or rock faces where unusual glide avalanches can release unexpectedly.
Snowpack Discussion
Weather and Snowpack
Storms moved across the Northwest at a nearly daily frequency the past few weeks with fluctuating but generally moderate snow levels. Two deep surface low-pressure systems moved across the Olympic Peninsula last week with the first passing last Thursday 3/10, and the next on Sunday, 3/13. These systems caused very stormy weather. Â
Cool and showery weather Monday and Tuesday with  prolonged westerly winds deposited additional snow at lower snow levels.
Storm totals on Mt Hood were impressive with about 4 feet of new snow accumulating over about 4 days ending Wednesday morning 3/16 at the NWAC Mt. Hood Meadows and Timberline stations! Â
The mid and lower snow pack at Mt Hood should generally be a stable mix of crusts and layers of moist and rounded snow crystals.
Recent Observations
The Mt Hood Meadows pro-patrol on Sunday 3/13 reported stormy conditions with widespread wind and storm slab of 6-12 inches on all aspects in the area, easily triggered by ski cuts and running on a crust buried on Thursday 3/10.
A report for Newton Canyon via the NWAC observations page for Monday 3/14 indicated stormy weather and numerous ski triggered 3-10 inch storm slabs.
On Monday and again Tuesday 3/14-15, control performed by Mt. Hood Meadows pro-patrol produced extensive and sensitive wind and storm slab avalanches triggered by ski cuts in lower elevation slopes and explosives in wind loaded terrain. Avalanches were greatest on N-E facing terrain. Loose wet slides were releasing on solar aspects by Tuesday afternoon below treeline.
On Wednesday 3/16, the Meadows pro-patrol were still finding hard wind slab of up to a foot above treeline on the usual lee aspects with a rising hazard of loose wet avalanches in steeper terrain below treeline due to warming and sunbreaks.
On Thursday 3/17 the Meadows pro-patrol reported strong east winds but not much snow available for transport. Small loose wet avalanches and rollerballs were seen only on direct solar slopes.
Avalanche Problems
Loose Wet
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.
A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.
Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1