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RegisterMar 21st, 2017–Mar 22nd, 2017
Mt Hood.
Above treeline, shallow fresh wind slabs should build near ridges. At lower elevations, re-freezing surface snow should maintain mostly stable snow. Watch for overhead hazard, such as recently formed large cornices along many ridges. These cornice releases are unpredictable and should garner your utmost respect.
Additional showers, mostly light to occasionally moderate, should persist Tuesday night through Wednesday. Significant cooling is expected through the day Wednesday.
The cooling Wednesday should allow for an overall decreasing danger. Previous moist to wet shallow surface snow should begin re-freezing and strengthening.
Only shallow snow from a few inches up to about 6-10 inches overlies the strong rain crust from 3/18 in most areas, mostly depending upon elevation and recent precipitation amounts.
Moderate to strong winds and showers at lowering snow levels should build some shallow fresh wind slabs at higher terrain along ridges, mainly on NW-NE-E facing terrain. Watch for firmer wind transported snow on all aspects, especially in areas of complex terrain.
At lower elevations, gradually re-freezing surface snow will form a new strengthening crust by later Wednesday.
It is always a good plan to travel well back from ridges, suspected of cornice formation, or on steep slopes below cornices.
Additionally, we have seen large cornice-fall avalanches that could trigger potentially very large wind-slabs formed during the last storm cycle or as new snow is added.
Weather and Snowpack
The first week or so of March was very cool and snowy. NWAC stations at Mt Hood piled up about 6-7 ft of snow.
The 2nd week of March was equally active with non-stop Pacific frontal systems pummeling the PNW. Unfortunately, these systems delivered far more rain than snow. At least two regional avalanche cycles occurred during the stretch. Significant snowpack consolidation occurred over this period due to rainfall and warmer temperatures.
After a short respite from the active weather pattern on Thursday, another strong low pressure system brought about an inch of predominately rain to the NWAC Mt. Hood stations Friday night and Saturday morning. Rapid cooling late Saturday morning was followed by snow showers with light new snow accumulation. Strong W-SW winds were transporting new snow above treeline by mid-day Saturday.
Sunday was cool with light winds and mostly sunny skies at Mt. Hood. Increasing clouds Monday with moderate daytime warming allowed additional slow snowpack settlement.
Light rain and snow showers Tuesday, 3/21 maintained shallow wet snow in lower elevation terrain. Above treeline, strong winds and light new snow, began to build shallow wind slabs on the leeward terrain, mainly below ridges.
Recent Observations
Mt. Hood Meadows pro-patrol reported a switch from rain to snow at mid-mountain by noon Saturday with strong W-SW winds beginning to build fresh new wind slab above treeline.
NWAC Observer, Laura Green was out Saturday and observed a snowscape of deep rain runnels from overnight rains. Along exposed ridges in higher elevations, wind slabs were forming along lee ridges as well as cornices.
Observations from Mt Hood Meadows Tuesday indicated light rain had maintained shallow moist to wet surface snow, but no natural or triggered loose wet avalanches were reported. Above treeline the strong winds and light snowfall began to build shallow wind slabs.