Avalanche Advisory

[Dan_Miller]

BACKCOUNTRY AVALANCHE STATEMENT FOR THE OLYMPICS WASHINGTON

CASCADES AND MT HOOD AREA

NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON

830 AM PDT TUE MAY 13 2008

 

NWAC Program administered by:

USDA-Forest Service

with cooperative funding and support from:

Washington State Department of Transportation

National Weather Service

National Park Service

Washington State Parks and Recreation Commission

Pacific Northwest Ski Area Association

Friends of the Avalanche Center

and other private organizations.

 

This statement applies to back country avalanche terrain below

7000 feet and does not apply to highways or operating ski

areas.

 

WAZ513-518-519-019-042-501-502-ORZ011-141700-

 

&&

 

..RAIN AND SIGNIFICANT WARMING TO PROVIDE SUBSTANTIALLY

INCREASING AVALANCHE DANGER THIS WEEK...

 

With the exception of a few periods of brief warming, an

unusually cool and snowy spring has been experienced in the

Northwest to date. This has produced periods of great late

season powder while maintaining a mostly stable and generally

refrozen mid snowpack below a diurnally developing layer of

moist to wet snow or slush in the upper 1 to 3 feet of near

surface snow. Field reports have indicated surface snow

conditions ranging from the good-a few inches of recent soft

snow over a firm base, to the bad-a trap crust over mush, as

well as a variety of conditions in between. The overall cool

conditions have produced some, though rather limited spring

avalanche activity as daily warming has slowly warmed and

weakened near surface snow. Most meltwater percolation and

associated snowpack weakening have been confined to upper

snowpack layers, at least at mid and upper elevations above

about 4 to 5000 feet.

 

However, this rather benign spring snowpack evolution is

expected to change significantly this week, when rain at

slowly rising freezing levels Tuesday into early Wednesday

should be followed by sustained high freezing levels reaching

13,000 to 15,000 feet later Wednesday through Saturday. These

prolonged and unusually high freezing levels for May are the

highest since last summer. In any case, rainwater weakening

and lubricating of near surface snow Tuesday should be rapidly

followed by increasing amounts of meltwater percolating into

and weakening progressively deeper snowpack layers. Combined

with some early winter faceting and weakening of several

layers near the ground, this sudden and sustained warming of

the Northwest snowpack should result in a significant spring

avalanche cycle, with some slides possibly involving all of

this past winter's snowcover.

 

An increasing moderate to considerable avalanche danger from

rain on Tuesday should precede a considerable to locally high

danger expected to develop in many areas mid-late Wednesday

through Saturday. While the rain affected danger increase

should develop on all exposures, sun and warming related

danger should initially develop most significantly on

southeast through southwest exposures Wednesday and Thursday.

However, its cumulative effects should progress to most

exposures and to increasingly high elevations later Thursday

through Saturday due to the combined effects of very warm

temperatures, high sun angle, substantial snow melt, light

winds and only minimal overnight refreezing of surface snow.

 

Due to the evolving danger, a variety of avalanches are likely

and should range from initial small wet loose releases to

increasingly large wet loose or wet slab slides, with some

isolated slides possibly extending full path length or more,

and some extending into relatively flat terrain runouts. As a

result, back country travelers from climbers to snowmobilers,

skiers to snowboarders, hikers to snowshoers, should all

exercise increasing caution in avalanche terrain Tuesday and

Wednesday, with travel in steeper avalanche terrain not

recommended Thursday through Saturday, especially on slopes

not experiencing recent avalanche activity. Travelers should

be especially cautious on slopes with overhanging cornices or

below icefalls, which may become very active later this week,

and may be the trigger for some of the larger slide releases

expected.

 

This statement will be updated as conditions warrant.

 

&&

 

 

[ashw_justin]

Combined with some early winter faceting and weakening of several layers near the ground, this sudden and sustained warming of the Northwest snowpack should result in a significant spring avalanche cycle, with some slides possibly involving all of this past winter's snowcover.

That would be a sight to see... from a safe distance. Would love to see photos if anyone sees it happen (I think I'm gonna pass anyway--skiing megamush would blow even if it weren't dangerous).

[ivan]

hey, it's gonna be 90 on friday - how bad could it be?

[armin]

Thanks for this.

[KaskadskyjKozak]

 

that puts a damper on a lot of routes :-(

[Bug]

that puts a damper on a lot of routes :-(

More like damp slush.

[mike1]

There goes my plans...

[olyclimber]

anybody have a favorite place to go with a high possibility of viewing big avalanches from relative saftey? (not human caused avies).

[Billygoat]

Mt. Baker Ski Area

 

White Salmon Lodge Parking lot

[G-spotter]

anybody have a favorite place to go with a high possibility of viewing big avalanches from relative saftey? (not human caused avies).

 

duffy lake road - which is closed right now with avvy debris blocking the road

[Raindawg]

anybody have a favorite place to go with a high possibility of viewing big avalanches from relative saftey? (not human caused avies).

 

From the Index Town Walls, I've seen MASSIVE avalanches come off the North Side of Mt. Index, especially down the chute between the North and Middle Peaks. It looked like Niagra Falls.

 

Also, I've seen giants come off of Eagle Peak in Mt. Rainier National Park across the road from Cougar Rock Campground (near where you do the log crossing of the Nisqually. The blast can knock your hat off.

[pms]

better yet, lake serene picnic

[Lowlander]

Or from the base of Ice Cliff glacier on Stuart to see the ice cliff break off, cornices falling, and ice/rock fall. Great sight to see, just witnessed it.

Edited May 17, 2008 by Lowlander