Issued: Fri, Mar 16, 2018 at 8AM

Expires: Sun, Mar 18, 2018

Above 2,500ft Considerable

1,500 to 2,500ft Considerable

Below 1,500ft Considerable

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Human-triggered slides remain likely in steep terrain.  We’re starting to get light freezes at night, forming a crust at the top of the snowpack and reducing free water. But underneath the crust, the snowpack is still wet from recent rains, warmth, and sunshine. Temperatures the next few days will be in the mid-upper 30’s F in middle elevations, and around freezing above 3,000ft. Solar radiation is expected to be strong.

1 meter down, we still have lingering persistent facets above and below the old January ice crust. We need several more days or a good freeze to solidify the midpack before these deep worries go away.

Problem #1: Wet Avalanches

Location: All slopes below 5,000ft (especially SE-S-SW aspects), 30 degrees and steeper. Heavy rain fell on the 12th up to about 4,000ft. The freezing level rose to 5,500ft on the 13th. A wet slide cycle occurred, and the snowpack is still quite moist. Sunshine will exacerbate the wet slide problem on sunny aspects. Human-triggered wet slabs and nasty sluffs remain likely on slopes steeper than 30 degrees. Natural slides may occur on sunny aspects as well. If the sun hits hard and temps are warm, there may be areas of HIGH danger. Surface wet slides may step down to the deep persistent facets 1m+ deep.

Problem #2: Persistent Slab

Location: All aspects above 1,500ft. About a meter down, we still have weak 3-4mm buried surface facets. This facet layer and ice crust underneath has caused many avalanches, and prolific collapsing over the last few weeks week. Remote triggering has been a common report. The slab on top could be anywhere from 80-150cm thick. Triggering is getting less likely, but remains possible, especially with wet slides that may step down.

Problem #3: Falling Cornices

Cornices aren’t as big or widespread this year as in previous seasons. However, there are still areas where large overhanging cornices exist. Give these areas a very wide berth. Stay way back. Strong sunshine/warmth this time of year has caused numerous close calls, accidents, and a few deaths due to collapsing cornices and snow ledges. 

Recent Avalanche Activity

There was a widespread avalanche cycle (March 10th-13th), mostly size D2-D3, a few D4, all aspects. Failure planes appear to have been both above and below the Jan. ice crust, within storm snow, and on depth hoar at the ground in some rocky areas. We’re still getting reports of whumphing, shooting cracks, and wet slide activity from the last three days.

 

Recent Weather

Very warm air arrived Tuesday, with freezing levels rising to 5,500ft. Light rain/snow fell Wednesday. We can expect mostly sunny, mostly calm conditions through the weekend, with light freezes at night and freezing levels rising up to 3,000ft during the day.

 Snow Depth [in] Last 24-hr Snow/SWE [in] Last 3-days Snow/SWE [in]  Today’s Freezing Level [ft]  Today’s Winds Next 24-hr Snow/SWE
Mount Ripinsky @ treeline
57″ 0″ / 0.00 0″ / 0.20 0 -> 3000  light, var 0″/ 0.00 *
Flower Mountain @ treeline
 47″ 0″ / 0.00 0″ / 0.20 0- > 3000 light, var 0″/ 0.00*
Chilkat Pass @ 3,500ft
 25″* 0″ / 0.00 * 0″ / 0.10 * 0 -> 3000 light, var 0″/ 0.00 *

( *star means meteorological estimate )

Additional Info & Media

If you get out on the snow, send in your observations!

Posted in Lutak Forecasts.
Erik Stevens

Forecaster: Erik Stevens