Avalanche Forecast

A strong front will move across the region overnight Wednesday and early Thursday, causing moderate to briefly heavy rain to high snow levels, about 7-8000 feet. Cooling and a change to snow showers is expected later Thursday with a change to light snow showers. It is hoped that the rain overnight Wednesday and early Thursday will trigger any remaining stubborn, persistent layers that may be present along the east slopes. These layers can be tricky to forecast just how much load will be needed, but it would be great to hit the reset button following the cooling later Thursday and beyond. We are continuing to list the early and mid January persistent slab problem as possible in the forecast until we get on the other side of this rain event and further observations confirm it is no longer an issue.

The main problem Thursday is expected to be wind slab in the above and near treeline zones as well as new storm slabs of heavy dense snow or wet surface snow stressing weaker underlying snow at all elevations. 

Rain or heavy wet snow should change to colder snow gradually through the day Thursday and diminish, beginning the freezing process of the wet snow and forming a strong bond to new snow and slowing the load to weaker underlying snow.

Weather

Two fair weather periods earlier this month allowed surface hoar and near surface faceting to occur. These persistent weak layers were buried intact on Jan 3rd and 11th and were reported throughout the Cascade east slopes.

A warm front last Thursday caused light or moderate amounts of snow which changed to freezing rain or rain east of the crest.

This was followed by cooler weather and some snow. NWAC stations along the east slopes indicate up to about 4 inches for the 2 days ending Sunday morning.

Warm air arrived Wednesday with freezing levels climbing to near 7000 feet.

Snow and Avalanche Observations

A report here on Turns All Year for the Clara Lake area near Mission Ridge on January 17th is dramatic.

See the NWAC YouTube page here for videos from Blewett Pass and Icicle Creek for January 18th.

NCMG guides travelling adjacent to Delancey Ridge, Friday, saw widespread evidence of the recent natural cycle with numerous crowns visible throughout the region. Many crowns were estimated to be about 1 meter.

NWAC pro-observer Tom Curtis was on Iron Mountain near Blewett Pass Sunday and found the January 11th layer 35-70 cm down on NW-SE aspects in the below and near treeline bands. He found that the buried surface hoar crystals are rounding and the tests gave low quality results and did not indicate propagation.

Tom was out again on Table Mountain near Blewett Pass on Monday in the 4-6000 feet elevation range and found the January 3rd and 11th layers well defined down 70 and 50-60 cm and still giving sudden planar results with ECT test indicating propagation. He also noted crowns from natural avalanches that released on the January 11th layer late last week.

Crown of persistent slab avalanche from about January 21-22 by Tom Curtis.

A report via the NWAC Observations page for Stemilt Basin near Mission Ridge strongly indicated that persistent weak layers at about 40 and 60 cm are still present east of the crest with test columns failing on isolation and evidence of previous widespread persistent slab avalanches.

Additional observations in the northeast WA Cascades Monday, looking for the buried January layers, indicated they may have been destroyed by rain a week ago. Though it's still too early to rule out this layer altogether, though in specific areas it may no longer be reactive.

Extensive professional observations in the Washington Pass area Wednesday, the 27th, have led to an updated forecast with concern for wind and storm slabs becoming more sensitive given the strength of the incoming frontal system tonight and early Thursday.