Issued: Thu, Mar 15, 2018 at 8AM

Expires: Thu, Mar 15, 2018

Above 2,500ft Considerable

1,500 to 2,500ft High

Below 1,500ft High

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 today in steep terrain.  The snowpack is still wet from rains, warmth, and sunshine. Last night’s freezing level was about 2500ft, and temperatures today 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. These weak layers have been well tested by several days of heavy precipitation, but still need a little more time to settle down. 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. Rain fell Monday night up to about 4,000ft. The freezing level rose to 5,500ft Tuesday. A wet slide cycle occurred, and the snowpack is still quite moist. Sunshine today will exacerbate the 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 will 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 week. Remote triggering has been a common report. The slab on top could be anywhere from 80-150cm thick, and will be sensitive to human triggering on slopes steeper than 30 degrees. 

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. 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. Temperatures will slowly cool down over the next few days. Light rain/snow fell Wednesday. We can expect mostly clear, mostly calm conditions through the weekend, with freezing levels at sea level at night, and rising up to 2,000ft during the day.

 Snow Depth [in] Last 24-hr Snow/SWE [in] Last 9-days Snow/SWE [in]  Today’s Freezing Level [ft]  Today’s Winds Next 24-hr Snow/SWE
Mount Ripinsky @ treeline
60″ 0″ / 0.20 57″ / 5.60 2000 -> 3000  light, var 0″/ 0.00 *
Flower Mountain @ treeline
 50″ 0″ / 0.20 38″ / 3.70 2000- > 3000 light, var 0″/ 0.00*
Chilkat Pass @ 3,500ft
 27″* 0″ / 0.10 * 20″ / 1.70 * 2000 -> 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 Transitional Zone Forecasts.
Erik Stevens

Forecaster: Erik Stevens