Urban Avalanche Advisory

Current Advisory as of

February 29, 2024

Expires 7:00 AM the following morning.

Issued By Tom Mattice

Danger Level: 2 - Moderate
View Danger Definitions

Today's Discussion

Tuesdays storm never quite materialized.  We picked up .2" SWE around the region which was less than 50% of the forecast amount.  Although dangers increased slightly they never quite hit considerable.  Today with lingering older wind slabs and with the potential for some shallow tender new wind slabs avalanche dangers remain Moderate with natural avalanches unlikely and yet human triggered avalanches remain possible in isolated wind loaded locations.  These wind slabs both older and new may be on opposing angles in the region, so although dangers are not widespread you need to be aware of lingering concern on most all aspects.

Yesterday natural avalanches were noted along the mainland in the Sunshine path and although a large powder cloud, not much snow in the deposition zones.   Although possible natural avalanches will become less likely today as we see prolonged periods of wind we see less wind available for transport and the snowpack tends to become stronger over time.

Wind loading remains the thing to watch as these slabs continue to potentially build.

Dangers are currently lingering at Moderate with human triggered avalanches still possible in wind loaded areas from the previous storm.  With no precipitation today after two days with  moderate winds avalanche dangers will be slowly falling over the next 24 hours.

We picked up 9-10" of new snow last Thursday into Friday.  Winds were quite strong during the event.  The tram had ese51mph winds and Eaglecrest had se72mph winds.  This started building our first wind slabs on N-W facing slopes in the region.  Saturday night we saw the switch to outflow winds.  Sheep Mountain saw n88mph Saturday night and n70mph Monday and again back to n52mph into today.  Mt Roberts also had notable winds with n42 Saturday night and n40 Yesterday.  The gauge is typically somewhat sheltered from this wind angle so you can assume you saw even more wind and loading in the urban paths.  Once in a while Eaglecrest will miss these outflow events or see much less wind and yet Saturday night winds at Eaglecrest also hit nnw35mph yet yesterday only n32mph.  Still more than enough to create some wind loading.

You now have wind slabs that have been built on opposing faces in the region.  Some perhaps older and somewhat stronger and yet some still new fresh, shallow and more sensitive to triggers.  Moderate winds continue today and yet the storm is drying out allowing conditions to improve over the next 24-48 hours.

Our storm last Thursday came in on top of what was a very warm wet snowpack.  This should have helped the new snow bond to the old snow surface a bit.  Temps fell throughout the storm as well which should help the storm slab overall to strengthen.  Storm totals were not all that great leading to a relatively stable snowpack and yet WINDS were the primary concern.

Tuesdays storm placed small additional load on these previous weak layers, building a new set of wind slabs that will be more easily triggered although shallower.  We do not expect to see activity large enough to be a concern in the urban interface.

Please continue to limit your exposure to wind loaded avalanche paths.

Currently its 5f on Sheep Mountain with nne31-40mph winds that peaked at n52.  Winds have been averaging over 25mph on sheep over the last 24 hours.

The tram is seeing  nne21-25mph winds that peaked at n40mph.  Temps here are 16f after a high of 17f.  No new snow was reported and yet you could see 2" of new on the gauges from wind loading.  Temps at Eaglecrest are currently 10f after a high of 17f.  Winds are currently only nne7-8mph.  Peak winds only hit n32.  Notably less wind loading occurred on Douglas than on the mainland.

Temps are forecast to remain cold over the next 2-3 days as things stay dry.  Forecast levels lead us to believe that avalanche danger will be decreasing and healing over the next few days.

The National Weather Service Forecasts-

Today- Mostly cloudy. Highs in the upper 20s. Northeast winds 10 to 15 mph.

Tonight- Partly cloudy. Lows 12 to 18. Northeast winds 10 to 20 mph.

Friday- Partly cloudy. Highs in the lower 20s. Northeast winds 10 to 15 mph.

Primary Avalanche Problem

Wind Slab

Problem Type:Wind Slab
Avalanche Size:Large
Avalanche Likelihood = Possible
Avalanche Trend = Decreasing Danger

Description

We picked up just over 2" new snow Tuesday during moderate winds with the tram peaking at n40 while Eaglecrest only saw n32mph and sheep mountain saw n52mph.  More than enough to build new shallow wind slabs that may be weak in isolated locations.

We picked up 9-10" of new snow last Thursday into Friday.  Winds were quite strong during the event.  The tram had ese51mph winds and Eaglecrest had se72mph winds.  This started building our first wind slabs on N-W facing slopes in the region.  Saturday night we saw the switch to outflow winds.  Sheep Mountain saw n88mph Saturday night and n70mph Monday.

Mt Roberts also had notable winds with n42 Saturday night and n40 again yesterday.  The gauge is typically somewhat sheltered from this wind angle so you can assume you saw even more wind and loading that this in the urban paths.  Once in a while Eaglecrest will miss these outflow events or see much less wind and yet Saturday night winds at Eaglecrest also hit nnw35mph and yesterday only n32mph.  Still enough to create some wind loading.

You now have wind slabs that have been built on opposing faces in the region.  Some perhaps older and somewhat stronger and yet some still new fresh and more sensitive to triggers.  Moderate winds continue today.   The storm has dried out and no real precipitation is forecast for the next few days.

Natural avalanches are not likely and yet human triggered events remain possible in isolated locations.

Our storm Thursday came in on top of what was a very warm wet snowpack.  This should have helped the new snow bond to the old snow surface a bit.  Temps fell throughout the storm as well which should help the storm slab overall to strengthen.  Storm totals were not all that great leading to a relatively stable snowpack and yet WINDS were the primary concern.

With only 2' new snow Tuesday and moderate winds we did see some shallow new slabs form that may be sensitive to human triggers in isolated locations and yet dangers are only moderate and continuing to fall.  A few natural avalanches were noted in the urban paths yesterday yet they were not all that large.

Learn more about Wind Slab.

Secondary Avalanche Problem

Loose Dry

Avalanche Size:Small
Avalanche Likelihood = Unlikely
Avalanche Trend = Decreasing Danger

Description

We didnt pick up that much new snow yesterday and yet it is very low density.  In steep open places you may see snow falling off of trees and rocks.  In super steep areas this may be enough to cause super shallow loose dry avalanches.  These are not forecast to be widespread nor of any size.  Its merely something to note as an additional weakness currently in the region.

With no snow in the forecast this condition will improve rapidly as snow settles and bonding improves today

Learn more about Loose Dry.

Today’s Avalanche Tip

As a community the more we know the safer the snow.  Are you seeing avalanche activity?  if so please report it at the Coastal Alaska Avalanche Centers website at http://CoastalAkAvalanche.org

This database is helping us to understand how widespread instabilities are and when activity is present and peaking...  Thank you for sharing.