Avalanche Forecast

Cool with light snow showers at times. Light snow accumulations expected with moderate ridge top winds, mostly from the NW. This should not significantly change the current danger and expect mostly shallow and stable snow conditions. 

If in areas receiving greater new snow, watch for wind transport building shallow wind slabs near ridges.

The recent warm, sunny weather has melted much of the early season snowpack and exposed terrain hazards, especially lower elevations. Expect terrain hazards with poorly covered rocks, vegetation and creeks, particularly on south-facing terrain, at lower elevations, and on exposed ridges where wind events have stripped much of the seasons snowcover.

Following 12 days of high pressure the first front crossed the Mt Hood area Friday. It wasn't much of a front as the high pressure weakened it significantly, with only a brief period of light rain and snow, New snow accumulations on Mt Hood have been a trace to 1 inch as of Friday afternoon.

The warm and sunny weather over the past 12 days has done a number on the early season snowpack throughout the region, returning many areas to very shallow early season conditions. The most consistent snowpack remains on shaded northerly aspects in the upper below treeline to near treeline where 3-6 feet remain.

The overall snowpack is stable with settled old snow sitting over the strong Thanksgiving rain crust, buried about 1-3 feet.

The high pressure, inversion regime over the past 12 days has created a widely varied array of surface snow conditions, including melt freeze crusts, settled old storm snow, and a mix of recently formed surface hoar or near surface facets (sugary snow) at lower elevations and some shaded terrain. 

Reports vary widely throughout the zones regarding the extent of the recent surface hoar and surface facet distribution. These persistent grain types will be an important distinction when greater loading occurs, but limited recent observations have not seen these conditions on the south side of Hood.. 

No human-triggered avalanches have been reported in over a week. Some natural small loose wet slides have occurred on mainly steep sun exposed slopes over the last week, but have become much less frequent over the past several days. Active wind loading has not been observed since late last week.

Observations

On Wednesday afternoon, Mt. Hood Meadows Pro Patrol reported consolidated snow and no avalanche concerns with some corn developing on south-facing aspects.

NWAC pro-observer Laura Green traveled in the Mitchell/White River drainage on Monday between 5300 and 6600 feet and found many variations in the surface snow but overall a settled and well bonded snowpack with few avalanche concerns in the terrain she covered. She observed surface hoar up to 3-4 mm on non-solar ENE-facing slopes. 

One skier triggered avalanche was reported on the White River Headwall near Crater Rock on Sunday up to size 2 (see picture).  While this slide reaches above NWAC's forecast, it highlights the potential for loose wet avalanches on steep solar aspects.  

Photo courtesy Mike Schumann 12-10-17