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RegisterFeb 15th, 2017–Feb 16th, 2017
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The threat of wet snow avalanches will maintain dangerous avalanches conditions Thursday. Wet slab avalanches are hard to predict and powerful due to the high water content, so extra caution is advised. Loose wet snow avalanches may begin small but entrain deeper layers. Shallow storm or wind slab may be found in the above treeline elevation band Thursday.
After a warming trend coupled with a wet Wednesday night, a slow cooling trend is expected to begin later Thursday with light to moderate showers. The threat of wet snow avalanches will maintain dangerous avalanches conditions Thursday. Wet slab avalanches are hard to predict and powerful due to the high water content, so extra caution is advised.
Loose wet snow avalanches may begin small but entrain deeper layers. Observations and tests for loose wet avalanches are more straightforward such as wet surface snow deeper than a few inches, rollerballs and natural loose wet avalanche activity.
Allow the snowpack to stabilize, avoiding steeper slopes and any avalanche terrain where even a small wet avalanche could have serious consequences.
Shallow storm or wind slab may be found in the above treeline elevation band Thursday, but will not be listed among the primary avalanche problems for Thursday.
Weather and Snowpack
The 2/8 - 2/10 storm cycle deposited 2-3 feet of snow in the Washington Pass area. In the central-east and southeast zones a rain crust formed with shallow amounts of new snow following at the tail end of the cycle. This storm cycle was a great test for any Persistent Weak Layers buried deeper in the snowpack. There was no evidence of any deeper releases and as a result, we have removed Persistent Slab from the problem list.
High pressure Saturday to Tuesday brought increasing sunshine and warming temperatures. Temperatures reached the 30's and 40's in many areas along the Cascade east slopes. This caused snowpack settlement, some small loose wet avalanche activity and a decreasing avalanche danger.
Another atmospheric river impacted the PNW on Wednesday. Light to moderate rain and snow with high snow levels occurred along the east slopes of the Cascades with localized freezing rain along the lower east slopes. Through 5 pm Wednesday, using the NWAC and NRCS Snotel networks, the southeast zone likely saw rain up to 7000 feet, 5000-6000 feet in the central-east and reports from Mazama indicated that it was still snowing in the valley. Washington Pass may have started off as freezing rain early Wednesday morning before a switch to snow.
Recent Observations
North
A report via the NWAC Observations page indicates a shallow climax slab avalanche on a north slope on Mt Patterson near Winthrop on Sunday. There is likely to be shallow faceted snow in this low elevation area.
NWAC observer Jeff Ward was out in the Silver Star and Cedar Creek drainages with NCH on Monday and reported minor loose wet avalanches on solar slopes and no other activity or signs on instability. Snow was still cold on north slopes in the 5000-9000 foot range.
Jeff was out again at Washington Pass on Tuesday and reported that slopes were cooler due to cloud cover with no signs of instability or avalanches.
Central
NWAC's Tom Curtis travelled in the Icicle Creek area near Cashmere Mountain Saturday 2/11. Tom did not get far as there was only a dusting of recent snow over a slick, firm crust. The greatest danger in this area was from uncontrolled falls on the slick crust as opposed to avalanches.
Another report via the NWAC Observations page for Dirty Face Peak for Sunday indicates that wind slab was unreactive there on Sunday.
Reports from the Mission Ridge pro-patrol mostly indicate a breakable surface crust from late last week and poor ski conditions Sunday and Monday.
South
No recent observations.
