... STRONG WIND THROUGH THIS AFTERNOON ...
TODAY ... MOSTLY CLEAR ... LOCALLY WINDY. HIGHS AROUND 37. NEAR
DOWNTOWN JUNEAU AND DOUGLAS AND OUT OF INTERIOR PASSES ... NORTHEAST WIND 20 TO 30 MPH WITH GUSTS TO 40 MPH...DIMINISHING TO 10 TO 20 MPH IN THE AFTERNOON. ELSEWHERE ... EAST WIND 5 TO 15 MPH.

TONIGHT ... CLEAR. LOWS 17 TO 27. NORTHEAST WIND 10 TO 20 MPH.
HIGHEST WINDS NEAR DOWNTOWN JUNEAU AND DOUGLAS AND OUT OF INTERIOR PASSES.

SUNDAY ... SUNNY. HIGHS AROUND 37. NORTHEAST WIND 10 TO 20 MPH. HIGHER GUSTS NEAR DOWNTOWN JUNEAU AND DOUGLAS AND OUT OF INTERIOR PASSES.

These minor Taku Wind events tend to load our start zones from the top, which is where we have the most snow already built up at the moment.

The wind picked up out of the NE about noon yesterday and has been blowing in the 30's on Sheep, 20's at the Tram. Probably going to climb even more this morning.

Main avalanche problem today is going to be developing wind slabs on W - S aspects. These slabs may, in turn, warm a bit in the afternoon sun, though temps are expected to remain colder overall. They never made it above -3c yesterday at the tram.

This combination of wind loading and sun is why the hazard will be rising through the day.

The snowpack has had a few days to settle out and bond since our recent cycle of storms that lasted from 3/7 - 3/18. In that time we got a bit over 150mm of water in five more intense snow events with scattered showers in between. This has changed the look of our alpine zones quite a bit ... looks like winter again up there.

Despite that, we have only recently filled in the start zones enough to get good slab continuity and sizes of slides are expected to be small.

Remember dry avalanches can run very fast and create damaging powder blasts in front of the moving snow.

Also note that while this forecast is a tool that we compile by looking at snow data from all over our local mountain ranges it is targeted at the slide paths that impact CBJ homes, roads, and trails, not general backcountry travel. There is a lot of spatial variability out there right now, and our start zones are not representative of many recreation zones.

Avalanche Danger for the urban zones is MODERATE today: Natural avalanches possible; human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas. Use caution in or under steeper terrain and in avalanche zones.

AVALANCHE FORECASTING

Our neighbors to the east have had a rough week. 8 deaths in BC and Alberta due to avalanches. As a result the canadian media is urging people to pay more attention to avalanche forecasts.

Here in Juneau if you are recreating in the mountains you kind of need to be your own forecaster as you go.

If you've read descriptions of being at the mercy of tumbling snow, you've probably figured out that avoidance is the only intelligent approach to avalanches. And a major part of avoidance is making good avalanche predictions.

Prediction remains as much art as science, wrote Edward LaChapelle, a godfather of avalanche research who worked at the University of Washington.

\"Known physical and mechanical principles of snow behavior provide a qualitative understanding of avalanche origin, but quantitative extension of these principles to specific situations is difficult, for nature presents too many variables to allow exact calculation of snow stress and strength variations with time. The precise time a given slope will avalanche cannot be predicted, but the general degrees of instability in a given area can be estimated with reasonable accuracy.\"

Translated: We forecasters can help, but you'll still have to watch your buns on those steep slopes...

A key part of avalanche forecasting is evaluating snow, often by digging snow pits and looking for specific weaknesses. Problem is, nobody wants to dig a pit on the steepest part of the slope, and what's true of one location may not be true of another.

Extended Column Tests developed in part in South East can be done on lower angle slopes to help avoid exposure though the high variability at the moment is still a problem.

Richard Armstrong, a snow-and-ice researcher at the University of Colorado, observes that avalanches reflect so many local factors that widely applicable forecasts are questionable.

\"You might be able to do a very good job of developing a model for one particular path -- say one that affects a road. But if you're responsible for the entire state, that's a very subjective thing.\" Nor does an accurate forecast mean that every slope will avalanche, Armstrong adds. \"A storm could trigger 20 percent of the avalanches, and the rest are still there, waiting for the next storm...\"

Some avalanche forecasters like to compare themselves to weather forecasters, who, as Colbeck notes, have a glut of money, data and supercomputers. Obviously we don't here at the Urban Forecast team.

Colbeck asserts that the atmosphere is transparent compared to snowpack, with its various layers, instabilities, sun exposures and slopes. Combine that opacity with the paucity of avalanche research, and you can predict the result: unpredictability. Still, Colbeck says that since the 1950s, avalanche researchers have made \"slow, steady progress. As we learn more about snow physics, develop better instruments for meteorology and measuring snow, better data relay techniques, and better education, we'll get some progress.\"

So will it ever be possible to predict avalanches with certainty? \"I don't see something that will solve this problem,\" Colbeck says.

That means you'll have to (The horror! The horror!) exercise some judgment...