945 AM PST TUE DEC 18 2007...corrected
 
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ZONE AVALANCHE FORECASTS

* OLYMPICS- WASHINGTON CASCADES NEAR AND WEST OF THE 
CREST- MT HOOD AREA-
Considerable avalanche danger below 7000 feet Tuesday. 
Danger gradually decreasing Tuesday night. Increasing 
danger Wednesday becoming high above 4 to 5000 feet and 
considerable below. Avalanche danger slightly 
decreasing Wednesday night.


* EAST SLOPES WASHINGTON CASCADES-
Increasing considerable avalanche danger above 5000 
feet and moderate below Tuesday. Avalanche danger 
slightly decreasing Tuesday night. Avalanche danger 
increasing Wednesday becoming considerable above 4 to 
5000 feet and moderate below, gradually decreasing 
Wednesday night.


SNOWPACK ANALYSIS

Additional new snow amounts as of early Wednesday ranged 
from about 6 to 14 inches in the Olympics, Mt Hood area 
and both west and east slopes of the Cascades. In 
general, recent storms over the past five days have 
deposited some 12 to 40 inches of snow over most Olympic 
and west Cascade slopes with up to 12 inches over the 
east slopes. 

Following the heavy rain event in early December about a 
ten day period of cool showery weather deposited 
occasional light snow fall as well as allowed for hoar 
frost development at times. These weak layers of low 
density snow or buried surface hoar formed a weak bond to 
the December crust and now have been loaded with the 
significant storm cycle snow of the past four to five 
days. This development has caused an increase in the 
recent avalanche danger with numerous recent avalanches 
having been reported over the past several days. Most of 
these slides have released near or on the old crust with 
some slides releasing in storm layers and stepping down 
to the old crust layer. 

Shear tests over the past couple of days have indicated 
that a slightly better bond is occurring at the crust 
interface, but not in all areas. Extra caution is advised 
as slides initiating in new layers may release to the 
crust which may be buried now 4 feet or more.

 
A similar but shallower structure might be expected along 
the Cascade east slopes. The greatest current danger is 
expected on lee slopes at higher elevations. 


TUESDAY AND TUESDAY NIGHT

A frontal passage should deposit additional new snow 
loading over Mt Hood and both east and west of the 
Cascade crest and Olympics Tuesday along with some strong 
crest level south to southwest winds. This should add 
further loading and unstable layers to underlying weak 
layers. Triggered slab avalanches are likely at higher 
terrain on lee slopes and increasing caution is urged in 
steeper terrain Tuesday. 

 WEDNESDAY AND WEDNESDAY NIGHT

Another very strong frontal passage is expected 
Wednesday. This should bring heavy snow and very strong 
crest level winds through the day Wednesday. This should 
cause a significant increase in the avalanche danger with 
mostly unstable snow developing above 4 to 5000 feet. 
Travel in avalanche terrain is not recommended above 
these elevations Wednesday. Decreasing snow and winds 
Wednesday night should begin to allow for a slowly 
decreasing danger. 


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