2.19.2007

new storm promises a deep powder day

So, I'm usually pretty good at heeding the warnings put out by the NWAC, but this one takes the cake. Crazy changing conditions in the northwest snopack. Am heading up to Alpental tomorrow morning for some freshies. Will be skiing with 2 others and returning in the late afternoon - definitely plan to be back before 5pm pacific. Will have full compliment of gear including tranceivers, shovel, probe, first aid, and provisions for a night or two.

Source: http://www.nwac.us/products/SABSEA

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BACKCOUNTRY AVALANCHE FORECAST FOR THE OLYMPICS WASHINGTON
CASCADES AND MT HOOD AREA
NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON
900 AM PST MON FEB 19 2007

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 forecast 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-ORZ011-201700-

&&

ZONE AVALANCHE FORECASTS

* OLYMPICS- WASHINGTON CASCADES NEAR AND WEST OF THE
CREST-

...AVALANCHE WARNING IN EFFECT FROM 4 PM PST MONDAY
UNTIL 4 PM PST TUESDAY...

Considerable avalanche danger above 4000 feet and
moderate below early Monday, gradually increasing
through Monday afternoon. Significantly increasing
danger Monday afternoon through early Tuesday becoming
high above 4000 feet and considerable below. Gradually
decreasing danger Tuesday afternoon and night becoming
high above 5000 feet and considerable below.

* EAST SLOPES WASHINGTON CASCADES-
Considerable avalanche danger above 6000 feet and
moderate below early Monday. Gradually increasing
danger Monday afternoon becoming considerable above
5000 feet and moderate below. Further increasing danger
Monday night and early Tuesday becoming high above 5000
feet and considerable below. Gradually decreasing
danger Tuesday afternoon and night becoming high above
6000 feet and considerable below.

* MT HOOD AREA-

...AVALANCHE WARNING IN EFFECT FROM 4 PM PST MONDAY
UNTIL 4 PM PST TUESDAY...

Considerable avalanche danger above 4000 feet and
moderate below early Monday, gradually increasing
through Monday afternoon. Significantly increasing
danger Monday afternoon through early Tuesday becoming
high above 4000 feet and considerable below. Gradually
decreasing danger Tuesday afternoon and night becoming
high above 5000 feet and considerable below.

SNOWPACK ANALYSIS
Very warm and sunny conditions Saturday helped to melt
and weaken surface snow on most open slopes. Cooling
Saturday night and light to moderate precipitation
deposited some 3 to 6 inches of new snow along most west
slope areas with up to 12 inches in the Mt Baker area.
This initial snow formed a relatively good bond to the
underlying wet and refreezing snow. Some reluctantly and
isolated ski triggered soft slabs were noted Sunday in
the shallow amounts of new snow from ski area
professionals. Also, very strong ridgetop winds scoured
much of the new snow on exposed slopes, exposing the hard
underlying crust. Continued light to moderate snow
showers Sunday morning through Monday morning have
deposited an additional 4 to 8 inches of new snow along
the west slope areas, Olympics and Mt Hood area.
Continued moderate to strong winds have likely built more
significant wind slab layers on many steep lee slopes,
mainly northeast through southeast facing slopes at
higher elevations where greater wind transport has
occurred. Snow pits early Monday morning at Snoqualmie
Pass noted a weak layer of grauple snow about 4 inches
below the surface at 3000 feet, likely deposited during
showers overnight. This or other near surface weak layers
have likely formed in the recent snow during fluctuations
of wind and snowfall intensity. Any triggered slides are
expected to release on these buried weak layers but may
fail or step down to the underlying crust where a weaker
bond exists, mainly above 5 to 6000 feet where
precipitation initiated as snow Saturday night.

Also, the strong winds and recent snowfall have built
extensive cornices along ridges and backcountry travelers
should be extra cautious near ridges.

Along the east slopes, significantly less new snow is
maintaining a lower danger, with shallow new snow
deposits over a very firm crust or breakable crust in
shaded areas.


DETAILED FORECASTS


MONDAY, MONDAY NIGHT
Light rain or snow Monday morning, gradually increasing
with moderate ridgetop winds. This should slowly increase
the danger as wind slab deposits increase over steep open
lee slopes. Further increasing rain or snow Monday
afternoon with strong winds. This should further increase
the danger early afternoon. Further increasing rain and
snow becoming heavy to very heavy Monday night with very
strong crest level winds. This should cause mostly
unstable snow to develop above about 4000 feet near or
west of the Cascade crest, Olympics, and Mt Hood area
where natural or triggered slides should become
increasingly likely late Monday. The greatest danger
increase should be on steep lee slopes near ridges,
mainly northeast to southeast facing. Travel in avalanche
terrain is not recommended by late Monday.

TUESDAY, TUESDAY NIGHT
Heavy snow early Tuesday at cooling temperatures and with
very strong winds should maintain or increase the danger.
Unstable slabs are likely on a variety of slopes,
especially northeast through southeast facing slopes near
or west of the Cascade crest, Olympics and Mt Hood area
where backcountry travel is not recommended. Slightly
less wind at lower elevations and less new snow fall
along the east slopes should limit the avalanche danger
increase, however unstable slabs are also likely on steep
open slopes at higher terrain. Decreasing snow showers
and further cooling with decreasing winds late Tuesday
and Tuesday night should allow for a slow decrease in
danger.

&&

Backcountry travelers should be aware that elevation and
geographic distinctions are approximate and that a transition
zone between dangers exists. Remember there are avalanche
safe areas in the mountains during all levels of avalanche
danger. Contact local authorities in your area of interest
for further information.

NWAC weather data and forecasts are also available by calling
206-526-6677 for Washington, 503-808-2400 for the Mt Hood
area, or by visiting our Web site at www.nwac.us. Also note
that field snowpack information is often available on the FOAC
website at www.avalanchenw.org, and weather and avalanche
glossaries for commonly used terms in the forecasts can be
found on the NWAC education page.

Kramer/Northwest Weather and Avalanche Center

$$

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