The avalanche danger is HIGH at upper elevations where natural avalanches are occurring. The avalanche danger is CONSIDERABLE inmid and low elevation terrain where human triggered avalanches are likely.
Travel in the highest elevation terrain is not recommended and cautious route finding should be used when traveling at mid and low elevations. Avoid travel on slopes steeper than 30 degrees or below steep terrain.
Natural avalanches have been reported this morning and will continue as long as it is snowing hard. I suspect at lower elevations where it is warmer the new snow is bonding quite well to the old snow surface.
New and developed pillows of wind drifted snow can be found in upper and mid elevation terrain. These areas of wind-drifted snow have now been buried under new snow and will be harder to see.
Watch for sensitive cornices primarily on north-east facing ridgelines where snow has been transported over the last twenty-four hours.
Any wind drifted avalanche may step down into a deeper buried weak layer resulting in a larger avalanche.
The deeply-buried persistent weak layer (PWL) from November continues to gain strength and it has become harder to initiate an avalanche on this layer. It may take a significant trigger - a large cornice fall, multiple riders on a slope, or another avalanche adding more weight to the snowpack to trigger this layer. Any avalanche triggered on this weak faceted snow would 2-7' deep. Areas where you are more likely to trigger this PWL are shallow thinner spots, rocky ridges, and mid elevation terrain such as Lambs and Parley's Canyon areas.
This report from Parley's Canyon still shows weak faceted snow buried under 3' of harder density snow.
Photo-Ambler shows how deeply buried those rounding facets are in White Pine
This morning ski area and highway operations reported natural avalanche activity.
Overnight mountain locations reported 8-12" of new snow and 1-1.3" of water. Storm totals are 11-18" snow and 1-1.65" of water. It is currently snowing, and the last few hours have been steady inch an hour snowfall rates.
Trailhead temperatures are in the mid to high 20's F while the temperatures at the 11,000' ridgelines are in the low 20's F. Winds are blowing southwest 30 gusting to 45 MPH at the 9000' ridgelines and west-southwest 35 gusting to 80 MPH at the 11,000' ridgelines.
Today will bring continued clouds and 5-9" of snow. Temperatures will be 30-34 F. Winds will blow from the southwest 30 gusting to 45 MPH at the 9000' ridgelines and west-southwest 40 gusting to 80 MPH at the 11,000' ridgelines. The freezing level will hover between 6,000' and 7,000' throughout the day.
The National Weather Service has issued a winter storm warning effective until 5:00pm on Wednesday. This morning's southerly flow storm will bring higher density snow before winds shift to the northwest bringing lower density snow Tuesday afternoon through Wednesday. Totals for the storm are 18-36" of snow and 1.8-3" of water.
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This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.
