BACKCOUNTRY AVALANCHE FORECAST FOR THE OLYMPICS WASHINGTON 
CASCADES AND MT HOOD AREA
NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON
835 AM PST THU FEB 05 2009 COR

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-ORZ011-061700-

&&

ZONE AVALANCHE FORECASTS

*	OLYMPICS-
*	WASHINGTON CASCADES NEAR AND WEST OF THE CREST FROM 
SNOQUALMIE PASS NORTHWARD-
*	CASCADE PASSES FROM SNOQUALMIE PASS NORTHWARD, 
INCLUDING STEVENS AND SNOQUALMIE PASSES-
Thursday: locally moderate danger on north through east 
exposures above 5 to 6000 feet, otherwise low avalanche 
danger slightly increasing
Thursday night: further slightly increasing avalanche 
danger becoming moderate above 5000 feet and low below
Friday morning: little change in the danger
Friday afternoon and night: gradually decreasing danger 
becoming moderate above 6000 feet and low below

*	WASHINGTON CASCADES NEAR AND WEST OF THE CREST SOUTH OF 
SNOQUALMIE PASS-
*	CASCADE PASSES SOUTH OF SNOQUALMIE PASS, INCLUDING 
WHITE PASS-
Thursday morning: low danger below 7000 feet
Thursday afternoon and night: slowly increasing 
avalanche danger becoming moderate above 4 to 5000 feet 
and low below
Friday morning: further slightly increasing danger
Friday afternoon and night: gradually decreasing danger 
becoming moderate above 5000 feet and low below 

*	EAST SLOPES WASHINGTON CASCADES-
Thursday morning: low danger below 7000 feet
Thursday afternoon and night: slowly increasing 
avalanche danger becoming moderate above 5 to 6000 feet 
and low below
Friday morning: further slightly increasing danger, 
mainly higher terrain near the crest
Friday afternoon and night: gradually decreasing danger 
becoming moderate above 6000 feet and low below

*	MT HOOD AREA-
Thursday morning: low danger below 7000 feet slightly 
increasing
Thursday afternoon and night: further slowly increasing 
avalanche danger becoming locally considerable on lee 
slopes above about 6000 feet and moderate elsewhere
Friday morning: little change in the danger
Friday afternoon and night: gradually increasing danger 
becoming moderate below 7000 feet

SNOWPACK ANALYSIS

DETAILED FORECASTS 
Although highly variable surface snow conditions continue 
early Thursday in most areas, the overall avalanche 
danger remains relatively low except for possible shallow 
wind slabs on sun shaded terrain in the northern WA 
Cascades and a recent slightly increasing danger during 
the later morning and afternoon hours on sun exposed 
terrain. These mostly stable surface snow conditions 
range from a varying strength melt freeze crust on most 
sun exposed terrain to breakable and somewhat faceting 
crusts on sun shaded terrain along with some patchy and 
shallow recent loose and faceting snow accumulations 
interspersed with the crusts. Also, in some steeper 
higher elevation sun shaded terrain that experienced 
significant avalanching with the early January rain 
event, field reports indicate that much of the 1 to 3 
feet of snow that has been deposited since then remains 
fairly fragile and faceted. Finally, some mainly small 
but highly variable surface hoar deposits have been 
forming overnight. While much of this hoar frost is being 
destroyed on a regular basis by either warming or 
sunshine, some deposits are persisting on steeper sun 
shaded terrain.  

Although some cracking and whumpfing was reported late 
last week and last weekend in some areas, presumably due 
to buried surface hoar or facets lying under shallow wind 
slabs or weak crusts, the very small amounts of recent 
loading have produced little stored energy and little 
stress on the variety of buried weaknesses, with a 
resulting low propagation potential for any local 
fractures that do initiate near cracks or whumpfs. 
Despite the rather good corn snow conditions that have 
developed on some steeper sun exposed southeast through 
southwest facing terrain over the past few days, 
challenging and somewhat hazardous travel conditions have 
also been reported on shaded northeast through northwest 
exposure terrain where a variety of varying strength 
breakable and faceted crusts or snow layers persist near 
the surface. Also in some steeper terrain, the 
development of increasingly strong crusts and some areas 
of blue ice should raise further flags of caution, as a 
slip or fall on such surfaces may result in a long and 
potentially dangerous slide for life on the smooth hard 
surface.

THURSDAY AND THURSDAY NIGHT
Increasing mid and high clouds Thursday morning should be 
followed by gradually lowering clouds mid-day and 
Thursday afternoon with some light rain or snow spreading 
northward Thursday afternoon and night along with 
significant cooling. This should produce a slow increase 
in the danger as mostly small amounts of new snow are 
deposited at gradually lower elevations, with moderate 
danger likely developing above about 4 to 5000 feet in 
most areas overnight. In the Mt Hood area where slightly 
heavier precipitation and strongest ridgetop winds are 
expected, locally considerable danger is possible on wind 
loaded southeast through northeast exposures above about 
6000 feet, as a weak bond of new snow to either an old 
crusted snow surface, areas of surface hoar or some near 
surface faceting. At lower elevations in all areas, 
smaller amounts of new snow and a better bond of the snow 
to the old snow surface should produce a slower and more 
limited increase in the danger. It should be noted that 
with the significantly lowering freezing levels, a rather 
poor bond is expected between the new snow and the wide 
variety of old snow surfaces above about 4000 feet in the 
north and 5 to 6000 feet in the south. In these higher 
elevation areas that receive any wind transport, this 
should result in gradual development of shallow but 
somewhat sensitive wind slabs.

FRIDAY AND FRIDAY NIGHTCORRECTED
Light to occasionally moderate snow should become mainly 
light snow showers Friday morning. Along with further 
cooling and mostly light ridgetop winds in the Olympics 
and most of the northern and central Washington Cascades 
Friday morning, this weather should maintain existing 
moderate danger in these areas above about 4 to 5000 
feet, where some shallow wind slabs are possible on lee 
slopes. However, in the southern Washington Cascades and 
Mt Hood area where stronger winds and slightly heavier 
showers are likely, a further slight increase in the 
danger is expected, especially on northeast through 
southeast facing slopes above 5 to 6000 feet where some 
sensitive 6 to 12 inch wind slabs are probable. Low 
freezing levels, decreasing light showers and winds 
Friday afternoon and some slow clearing Friday night 
should allow for gradually decreasing danger as new, 
generally shallow wind slabs begin to settle.   

&&

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.

Moore/Northwest Weather and Avalanche Center

$$