Avalanche Forecast
Regions: Mt Hood.
Yet another storm will impact Mt. Hood on Thursday with increasing rain and snow, wind and rising snow levels. Travel in avalanche terrain is not recommended on Thursday due to the very dangerous avalanche conditions expected.
Detailed Forecast
A weak low pressure system should produce another 12-18 inches of snow for Mt. Hood Wednesday afternoon and night. A warming trend Wednesday night should produce a spike in avalanche activity overnight.Â
However the main event will be the storm system forecast Thursday through Friday morning.  A low pressure system tracking north across Washington State will bring increasing precipitation during the day Thursday to Mt. Hood. This will be accompanied by a continued warming trend with snow levels peaking around 8000 feet Thursday afternoon.Â
All of these weather factors will stress the upper snowpack still struggling to settle and stabilize. The warming trend and increasing snowfall at higher elevations will increase the likelihood of new storm slab layers.
Deep wind slab should be watched for on all aspects but should be found mainly on NW to SE aspects due to recent SW to W winds. Watch for firmer wind transported snow on varied aspects especially in areas of complex terrain.
Loose wet avalanches will become more likely as rain becomes heavier and pushes higher up the mountain. Loose wet avalanches on steeper slopes may become large and entrain a significant amount of recent snow.Â
Cornices won't be listed as an avalanche problem but avoid travel on ridges near where cornices may have formed and avoid steep slopes below cornices that may fail at any time.
Snowpack Discussion
Weather and Snowpack
The most recent wet warm storm arrived on Valentines Day 2/14 and formed the uppermost very strong rain crust in our snowpack.Â
Strong southwest flow carried a strong front across the Northwest on Friday evening March 3rd. At Mt Hood this caused strong southwest alpine winds, heavy, moist, dense new snow above about 4000 ft and wet snow or rain below about 4000 ft.
NWAC stations at Mt Hood have had about 4Â ft of snow in the past 3Â days during the ongoing storm cycle.
Recent Observations
The Meadows patrol on Tuesday morning reported strong winds and heavy snowfall but with limited avalanches. Upside down wind slab layers were building with lots of snowpack cracking and whoomping due to wind slab on ridges. Patrollers released 2 sensitive cornices remotely.
Warming, strong W-SW winds and heavy snowfall Tuesday caused a very large natural avalanche cycle according to the Mt. Hood Meadows pro-patrol by early Wednesday morning.
Avalanche Problems
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: Very Likely
Expected Size: 1 - 2
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Very Likely
Expected Size: 1 - 2
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: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 1