Avalanche Forecast

Strong southwest flow aloft will carry a very moist frontal system to the Northwest on Wednesday. This will cause varied weather along the Cascade east slopes on Wednesday. Moderate to heavy snow is expected in the northeast Cascades such as at Washington Pass. But a change to rain should be seen in the central east and southeast Cascades. See the NWAC Mountain Weather Forecast for details.

Wednesday will be a potentially dangerous day along the Cascade east slopes where different avalanche problems will be forecast depending on location.

In the northeast Cascades expect moderate to heavy snow on Wednesday. This is expected to build new potentially deep wind and storm slab layers. Natural or triggered large wind and storm slab avalanches are likely in this area on Wednesday. Travel in avalanche terrain is not recommended in the northeast Cascades on Wednesday.

The change to rain in the central east and southeast Cascades makes loose wet or wet slab more likely to be the avalanche problems is these areas. Natural or triggered small to large loose wet and wet slab avalanches are possible in these areas on Wednesday depending on how much rain there is, how it percolates into the snowpack and if avalanches 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 actiivity. But observations and tests for wet slab avalanches are more difficult since it is usually hard to know the effects of significant amounts of water percolating into the snowpack. Cautious route finding and careful snowpack evaluation will be required if you decide to travel in the back country of the central east and southeast Cascades on Wednesday.

Remember that the types of avalanche problems to watch for depend on the weather. If the weather is different than expected you will need to watch for different avalanche problems.

 

 

Weather and Snowpack

The last strong storm cycle 2/8-2/10 deposited 2-3 feet of snow in the northeast Cascades such at Washington Pass. However the aftermath of the same storm cycle in the central east and southeast Cascades left a crust with whatever amount of new snow received above, except for areas exposed to winds which may have remained scoured to the crust.

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 brought snowpack settlement, some small loose wet avalanche activity and a decreasing avalanche danger.

The last storm cycle was a great test for any Persistent Weak Layers that we have not had good confirmation about. There was no evidence of any deeper releases as a result of the recent cycle and as such we will remove the Persistent Slab from the problem list.

Recent Observations

North

NWAC pro-observer Jeff Ward covered a significant amount of terrain in the Washington Pass zone Sunday. The few days of snowpack settlement, warming and sunshine have allowed for the 2-3 feet of recent storm snow to stabilize significantly by Sunday. Snowpack tests were negative Sunday and no triggered avalanches occurred. The avalanche problems were shifting away from storm related problems to warming and sunshine related dangers.

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.

Jeff was out again in the Silver Star and Cedar Creek area with the NCHG 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

A large avalanche off of Dirty Face Peak knocked in a garage door of a house on the north shore of Lake Wenatchee around 1130 am Thursday 2/9.

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. Observations were not made in higher elevation terrain where wind slabs may have formed.

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 bad skiing on Sunday and Monday.

South

No recent observations.