Avalanche Advisory Archive 2016 – 2018
|Date Issued:||2017-02-12 07:03:47|
With 35 to 65cm of new snow in the last 24 hours coming in during 30-70mph winds placing a heavy dense load on top of a ligher layer on a bed surface that is old hard and icy... You have all the ingredients in place for an avalanche.
The natural loading is reduced a little with slower wind speeds this morning but it continues none the less. With temps warming up through the point of freezing today this will also highten the concern of activity on this layer.
BE SAFE OUT THERE FOLKS>
We saw huge precip and snow volumes around the region yesterday. This came in on an old icy bed surface that was age and wind hardened. New Snow will likely not bond well to this surface.
This storm was also upside down and continues to be. With several degrees of warming during the storm and more in the forecast today up through the point of freezing this adds to the concern.
Choose your terrain carefully today folks... avalanche danger is HIGH on ALL SLOPES...
The National Weather Service Forecasts-
Today- Rain mix with snow at times north of the airport. widespread rain showers in the afternoon. Little or no snow accumulation. Snow level 400 feet. Highs around 39. Southeast wind 10 to 20 mph.
Tonight- Rain...heavy at times. Snow level 1200 feet in the evening. Lows around 38. Southeast wind 10 to 20 mph.
Monday- Rain. Highs around 44. Southeast wind 10 to 20 mph.
GOOD MORNING JUNEAU>>> Are we paying attention out there?
AVALANCHE DANGER IS HIGH TODAY> Natural avalanches are possible and human triggered avalanches are more than likely.
We picked up a great deal of precipitation around the region yesterday during a very windy storm. This precip started as cold dry snow on an old icy bed surface in places. Then we cranked up the wind and increased the densities a bit placing a slab on a weak layer over a slide prone bed surface. All the ingredients are in place for avalanches.
Yesterday conditions started off a bit cooler and warmed 3f degrees during the day. This morning Eaglecrest is showing 32f at the base, 29f mid mountain and 29f on top. Roberts is slightly warmer but still holding freezing temps at 31f.
Winds have slowed a bit this morning and are currently 22mph gusting to 24 at Eaglecrest and 10-15 at the tram. More than enough for continued windloading. Remember these winds were upwards of 40-70mph yesterday during the peak of the storm.
Here are the big numbers. From the gauges it looks like Eaglecrest picked up 35cm of snow at least with 55mm of precipitation... So quite dense snow on top of what started at 10% snow. Mt Roberts is showing crazy numbers this morning with 66cm of new snow coming from 66mm of precip... which is possible... but my guess is this is much denser than 10% snow. We may have seen 66mm of precip... but my guess is that was a lot less than 66cm of new snow... my guess here is this greater snow number than Eaglecrest is primarily from a great deal of snow drifting... showing you for example between eaglecrest and the tram you could see anyplace from 35 to 66cm slabs and these are storm slabs not so much just in windloaded areas... My assumption is there are some monster slabs in windloaded areas and we have probably seen some natural avalanche activity already overnight.
Todays forecast calls for another 3/4\" precipitation with 10-25mph winds in the mountains. But the big thing here is today's forecast into tomorrow is calling for as much as another 10f of warming... and this warming is up through the point of freezing and beyond. This should start a natural avalanche cycle in places. If the forecast precip totals were higher you could bet on it... but my guess is you will see natural avalanche activity through later today into tomorrow.
Be aware that the snowpack is very near a state of failure in many places right now. We have placed a great load on it in a short period of time over an old, hard, icy bed surface. The avalanche is simply awaiting a trigger... DONT BE THE TRIGGER>
Choose your terrain wisely today. Be conservative. Ride with a partner. Remember Transceiver, Probe, and Shovel... Safe Spot to Safe Spot with spotters in place... find your zen and choose the line with the lease consequence. Be safe out there and have a great day.
Here is a link to a great article on:
How Not to Die ? Evaluating consequence, vulnerability and exposure