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It will be possible to human trigger wind slabs, dry loose, and persistent slab avalanches today.
Steady easterly winds over the last 24 hours have transported old snow and built fresh wind slabs on westerly aspects at the upper elevations. Expect these to be small in size, but easy to human trigger. This is the primary hazard today.
Conditions have been rather stale since the Election Dump. On a positive note, cold temps have recrystallized the snow . Conditions include square powder, sun crust, and wind crusts. The snowpack varies in depth from 6″ to 2.5′.
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Travel Advice | Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. | Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. | Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. | Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. | Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain. |
Likelihood of Avalanches | Natural and human-triggered avalanches unlikely. | Natural avalanches unlikely; human-triggered avalanches possible. | Natural avalanches possible; human-triggered avalanches likely. | Natural avalanches likely; human-triggered avalanches very likely. | Natural and human-triggered avalanches certain. |
Avalanche Size and Distribution | Small avalanches in isolated areas or extreme terrain. | Small avalanches in specific areas; or large avalanches in isolated areas. | Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. | Large avalanches in many areas; or very large avalanches in specific areas. | Very large avalanches in many areas. |
No new slab avalanches have been observed since Nov. 10. Steady winds overnight and through today will make human triggered small, shallow wind slabs possible. Keep your eyes peeled for this bull-eye clue for this hazard.
This week we observed small human triggered loose dry avalanches on north facing, steep terrain at the upper elevations. This problem will be present this weekend on all aspects, on steep slopes, 40° and steeper.
Signal Word | Size (D scale) | Simple Descriptor |
Small | 1 | Unlikely to bury a person |
Large | 2 | Can bury a person |
Very Large | 3 | Can destroy a house |
Historic | 4 & 5 | Can destroy part or all of a village |
Easterly winds increased on Friday and will remain steady through the day. Wind slabs have formed overnight and will continue to form throughout the day.
Expect 2-6″ thick, small wind slabs, on W to N aspects, at the upper elevations, on slopes 35° and steeper, to be possible to human trigger. Wind slabs will be thicker near ridgelines and therefore more consequential.
Shooting cracks are red flags of this problem. Hand pits can easily identify the stiffer snow failing on the old snow surface. Look for smooth, freshly drifted snow to identify the presence of this problem.
Winds are predicted to taper tonight and into Sunday. Expect wind slab instabilities to decrease within 24-48 hours, once the winds calm down.
Signal Word | Size (D scale) | Simple Descriptor |
Small | 1 | Unlikely to bury a person |
Large | 2 | Can bury a person |
Very Large | 3 | Can destroy a house |
Historic | 4 & 5 | Can destroy part or all of a village |
Cold temperatures this week have contributed to faceting in the snowpack. As a result, small dry loose avalanches (sluffs) will be possible to human trigger in steep terrain above 40° and in specific locations. In some protected locations, the entire snowpack consists of facets which in steep terrain funneling into a terrain trap can compound the risk of a small avalanche. Although we expect these sluffs to be small in size, early season rock hazards can increase the consequence of any avalanche.
Signal Word | Size (D scale) | Simple Descriptor |
Small | 1 | Unlikely to bury a person |
Large | 2 | Can bury a person |
Very Large | 3 | Can destroy a house |
Historic | 4 & 5 | Can destroy part or all of a village |
Persistent slabs up to 1.5′ thick will be possible to human trigger today in isolated locations on all aspect at upper elevation.
Stability has been steadily improving despite the atrocious snowpack structure. A benign weather pattern with cold temps, light to moderate winds, and no recent precipitation has not aggravated our snowpack. You can expect stability to steadily improve until another significant loading event. At that point, expect our weak layers and faceted snowpack to react angrily.
The Persistent Slab problem continues to linger, but the likelihood of triggering has decreased substantially. Anticipate finding this avalanche problem in isolated locations where stiff snow overlies weaker snow near the ground. Probing the snowpack is a useful tool for identifying this hidden structure as are pole tests and hand shears.
The pit below was conducted in a targeted location which is not representative of the snowpack as a whole, but is representative of isolated locations where triggering a slab may be possible. It is important to note that while the test here appears drastic in it’s result, we could not produce shooting cracks or significant collapsing of the snow pack while traveling over this snowpack on skis. Expect the poor structure in this location to become more problematic after the next storm.
NWS Rec Forecast here.
NWS point forecast here.
State Parks Snow Report and Motorized Access information here.
No new precipitation this week.
Winds increased on Friday and remained steady overnight.
Marmot Weather Station last 24 hours
|
Temp
|
RH
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Spd
|
Gust
|
Dir
|
---|---|---|---|---|---|
Min | 16.6 | 49 | 5 | 11 | ENE |
Max | 23.9 | 66 | 15 | 24 | SE |
Average | 20.5 | 56.5 | 10.7 | 17 | E |
Independence Mine Snotel last 24 hours
|
Temp
|
RH
|
Spd
|
Gust
|
Dir
|
|
|
SWE
|
SnoHt
|
|
|
---|---|---|---|---|---|---|---|---|---|---|---|
Min | 19 | 38 | 2 | 2 | N | 4 | 19 | ||||
Max | 29 | 54 | 8.8 | 17 | NNW | 4.3 | 20 | ||||
Average | 23.7 | 44.2 | 3.8 | 9.1 | NNE | 4 | 19 |