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RegisterMar 12th, 2017–Mar 13th, 2017
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Mother Nature will throw a lot of serious avalanche problems at us again on Monday. The exact outcome of the snow, rain and warmer temperatures is hard to predict but we have to expect multiple types of potentially large or very large avalanches. Very dangerous avalanche conditions are expected in the above treeline areas east of the crest on Monday and travel in avalanche terrain is not recommended in these areas. Careful snowpack evaluation and cautious routefinding will be required in other areas.
A front should sag slowly south over the Northwest on Monday. Waves of moisture moving along the front should cause a very wet day in the Olympics and Cascades. Periods of moderate to heavy rain or snow should be heaviest along the Cascade west slopes with rising snow levels.
Mother Nature will throw a lot of serious avalanche problems at us again on Monday. The exact outcome of the snow, rain and warmer temperatures is hard to predict but we have to expect multiple types of potentially large or very large avalanches.
Loose wet avalanches are very likely in areas of wet snow or rain.
Avoid areas on ridges in the Northeast zone where there are potential cornices and slopes below cornices. Cornices will be weakened and prone to failure on Monday due to loading by wet snow and rain and warm temperatures. Large cornices have been reported from many areas and have been involved in recent accidents and close calls.
New sensitive storm slab is most likely above treeline in areas that receive more than a few inches of rapidly accumulating snowfall.
New or previous wind slab should be suspected mainly on NW-SE aspects above treeline due to recent SW-W winds. But watch for firmer wind transported snow on all aspects especially in areas of complex terrain.
The persistent slab problem was returned to the Northeast zone due to recent avalanches and some reactive tests on the Valentine's Day or 2/17 crust. Avalanches stepping down to these depths would be large and very dangerous.
Very dangerous avalanche conditions are expected in the above treeline areas east of the crest on Monday and travel in avalanche terrain is not recommended in these areas. Careful snowpack evaluation and cautious routefinding will be required in other areas.
Weather and Snowpack
The first week or so of March was very cool and snowy. NWAC and NRCS stations indicate about 2 feet of snow in the northeast Cascades with less elsewhere along the Cascade east slopes. This gave the snowpack a test and caused an avalanche cycle of several types of avalanches in the Cacades.
A strong frontal system brought increasing precipitation and winds along with a warming trend to the Cascades on Thursday. On Thursday night rain may have pushed up to about 4000 feet in the northeast Cascades and about 5000 feet in the southeast Cascades. By Friday morning NWAC stations along the Cascade east slopes had about .35-.9 in of WE with only 0-5 inches of snow mainly in the northeast Cascades.
Another front crossed the Cascades on Saturday causing more SW-W winds, snow at higher elevations, and rain at low elevations. It looks like there was up to a few inches of new snow east of the crest on Sunday morning.
Recent Observations
North
On Wednesday, the NCMG on Delancey Ridge observed crowns from recent natural storm slabs about 20-30 cm deep on S-SW aspects near and above 5500 feet. In a test pit on a SE aspect at about 5400 feet, the 2/17 melt freeze crust gave hard but sudden planar results in compression tests failing on facets above the crust.
The NCMG were out again on Thursday near Washington Pass and report a 2/17 crust and the Valentine's Day layer at about 80-130 cm down. Deep tap tests of the Valentine's Day crust at 95 cm on gave results 1 out of 4 tests; PSTs gave results that ranged from no result to PST End so there is variation in the reactivity of the Valentine's Day layer.
On Saturday a report for Delancy Ridge via the NWAC Observations page indicates many natural large loose wet avalanches on solar slopes.
The NC Heli Guides on Saturday report significant recent warming and settlement. Recent natural size 1.5-2 wind and storm slab were seen in the Silver Star area. Pits in the upper Willow drainage had generally right side up layers with the Valentine's Day crust seen at 100-128 cm.
The NC Heli Guides were in the Varden and Silver Star area on Sunday and reported many touchy natural and 1 triggered size 1-2 storm slabs on steep north slopes in the 5200-8400 ft range. Some cracking and propagation was also seen though no releases.
Central
The Mission Ridge patrol reported surprisingly minor results during avalanche control Thursday morning 3/9 despite the new snow and west winds. The new snow was generally bonding well with only a few areas of soft wind slab releasing below ridge-lines. The releases were shallow and did not step down to any deeper layers.
South
No recent observations.