Issued: Tue, Mar 27, 2018 at 8AM

Expires: Wed, Mar 28, 2018

Above 2,500ft Moderate

1,500 to 2,500ft Low

Below 1,500ft Low

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Last night’s new snow will probably not amount to enough for any new storm snow concerns. However, if heavy snow begins piling up today, or winds are causing fresh wind loading, keep an eye on the new snow to be building tender slabs sensitive to human triggers.

Problem #1: Wind Slab

Location: Wind loaded and cross-loaded E-S-W aspects above 1500ft. 2-6″ of snow fell in this zone last week. Winds blew hard out of the north Wednesday-Friday, causing significant wind loading on S aspects and cross loading E and W aspects with wind slabs 15-30cm thick. Human triggered avalanches remain possible with these wind slabs at the top of the snowpack in loaded areas. Test slopes, ski cuts, and hand shears will be useful tools to evaluate bonding of these slabs and the danger on a particular slope. Always utilize safe terrain and group management techniques. 

Problem #2: Deep Slab

Location: All aspects above 1500ft. Confidence: Low Now that the midpack is solidly re-frozen, a strong bridge exists over the main weak layer (old facets 1m deep in the Lutak zone and 30-45cm deep in the Pass). In most areas, it will be nearly impossible to penetrate the upper frozen ice layer. BUT, in areas where the snowpack is thin, it may still be possible to trigger basal facets or depth hoar which could propagate into areas of deep slab. The likelihood of this happening is generally low, but still possible. Use extra caution to avoid thin rocky areas at the margins of a slab. Be careful when approaching summits, ridges, and other windswept areas. Unsupported slopes will be most likely to slide in this scenario.

Recent Avalanche Activity

During the freeze-thaw conditions over the weekend (March 17th-18th), reports from the field included one human-triggered wet slide at the Pass, and isolated whumphing/collapsing still happening in all zones.

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.

Recent Weather

Snow totals from last night are around 2-3″. Light snow will continue today and tonight, with some snow and clouds lingering Wednesday. Winds will be moderate North, turning moderate South today. 

 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
61″ 2″ / 0.15 2″ / 0.15 0  mod, var 2″/ 0.20 *
Flower Mountain @ treeline
 45″ 2″ / 0.15 2″ / 0.15 0 mod, var 2″/ 0.20*
Chilkat Pass @ 3,500ft
 26″* 2″ / 0.15 * 2″ / 0.15 * 0 mod, var 2″/ 0.20 *

( *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