Urban Avalanche Advisory

Current Advisory as of

February 24, 2021

Expires 7:00 AM the following morning.

Issued By Tom Mattice

Danger Level: 3 - Considerable
View Danger Definitions

Today's Discussion

Although avalanche control on Thane Road did not get many results avalanche danger remains CONSIDERABLE today.  Natural avalanches remain possible although are less likely today with decreased loading rates over the last 2 days with cool temps.  Human triggered avalanches remain likely.  These may not be wide spread but we are continuing to see human triggered avalanches.  See pics below for a snow machine remotely triggered avalanche from yesterday on Douglas Island.  Be aware the beast is still lurking.  These slides were triggered from below while playing in a safe area the settlement created a remote trigger for this event.

We have the potential for large wind slab avalanches in specific areas and very large persistent weak layer avalanches in isolates areas.  although we are not seeing a lot of activity like we did during the storm its important to recognize these slides are of notable size and hard slabs with quite long fracture propagation.  These are dangerous events to be managed and should be avoided.  Terrain selection remains the key to safety.  Please continue to limit your exposure to avalanche terrain and use mindful safety practices if you choose to recreate in avalanche terrain.

We have multiple weak layers in the snowpack.  The storm total for the last week after settling was 57cm yesterday in my study plot most all avalanches will potentially be at least this deep.  This storm snow is sitting on a rain crust over a bed of facets that remain quite weak.  We also have multiple persistent weak layers deeper in the snowpack that have shown weakness and the ability to produce avalanches over the last few weeks with human triggered slides over 4-5' in depth.  We could see avalanches up to a meter deep in these weak layers and in wind loaded locations these weak layers can even be much much deeper.  Remember the Eaglecrest avalanche from Sunday was 6-7' deep at the crown.

Although much of the activity has been on lee slopes due to increased loading rates from the wind we have actually seen avalanches on multiple aspects in the region as the weak layer is present on most all aspects.

Weather-

Eaglecrest Top Temps Low- 23f, High- 25f, Current- 24f.  Winds SE19-30 with peak gusts to SW50mph in the last 24 hours.   1cm new snow.  1mm SWE.

Mt Roberts Tram Temp Low- 26f, High- 29f, Current- 27f.  Winds SE18-21mph peak gusts to SSW35mph in the last 24 hours.  5cm new snow, 3mm SWE.

The National Weather Service Forecasts-

Today- Cloudy. Chance of rain and snow in the morning, then rain. Near steady temperature in the mid 30s. Southeast winds increasing to 15 to 25 mph with gusts to around 40 mph in the afternoon.

Tonight- Windy, cloudy. Snow and rain likely. Snow accumulation around 1 inch. Lows in the lower 30s. East winds 20 to 30 mph with gusts to around 45 mph becoming north 10 to 15 mph late.

Thursday- Cloudy. Numerous rain and snow showers. Snow accumulation up to 1 inch. Highs in the mid 30s. Southwest winds 10 to 15 mph.

Todays forecast calls for as much as 8" new snow in the hills over the next 24 hours.  With continued winds this will keep avalanche danger considerable.

Primary Avalanche Problem

Wind Slab

Problem Type:Wind Slab
Avalanche Size:Large
Avalanche Likelihood = Likely
Avalanche Trend = Steady Danger

Description

With the high winds early in the storm and consistent wind during the entire storm we are definitely seeing more activity on lee slopes due to the increase loads and yet winds are not the only concern.

We have persistent weak layers on most all aspects and storm slabs also remain a concern.  We have seen remote triggering of the storm slab from hundreds of yards away.  Recognize you dont have to be in avalanche terrain to start an avalanche.

PLEASE USE EXTREME CAUTION IF YOU CHOOSE TO GO INTO THE MOUNTAINS RIGHT NOW>  CONDITIONS ARE SPOOKY>

Learn more about Wind Slab.

Secondary Avalanche Problem

Persistent Slab

Problem Type:Persistent Slab
Avalanche Size:Very Large
Avalanche Likelihood = Possible
Avalanche Trend = Steady Danger

Description

We have multiple persistent weak layers in the region up to a meter deep in non wind loaded locations.  In wind loaded locations these weak layers are even deeper.

Although difficult to trigger these are now deep hard slabs and have considerable danger.  We are seeing remote triggering of avalanches with fractures running hundreds of yards.

Please limit your exposure to avalanche terrain.

Learn more about Persistent Slab.

Today’s Avalanche Tip

Please continue to share your observations at the Coastal Alaska Avalanche Center @ http://CoastalAkAvalanche.org