Bollettino valanghe

Northwest Coastal

Jan 2 – 3, 2022Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 5 years ago

Pericolo valanghe

Tue
Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
Apri la mappa completa

In sintesi

Keep your guard up! The storm may be tapering, but human triggering remain likely.

Diligently watch for changing conditions throughout the day. Easterly winds may create slabs in atypical locations and at lower elevations than you might usually expect.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–3.5

    Yesterday a large storm impacted the region bringing upwards of 80 cm of new snow. The associated strong to extreme winds have built deep deposits of slab in wind exposed areas. In sheltered areas, this new snow fell on a weak layer of near surface facets. The poor bond to the underlying surface means a touchy loose dry or storm slab problem may persist. 

    A change in the weather pattern today is bringing strong southeast outflow winds which will effect all elevations. Expect fresh, reactive wind slabs to be forming in atypical reverse-loading and cross-loading areas, and down to lower elevations than you might usually expect.

    Two layers of surface hoar have been reported within the upper snowpack in protected areas at treeline and below; one is down 40-60 cm (Dec 21) and the other is down 60-100 cm (Dec 18). They have not produced any avalanche or snowpack test results and their distribution seems fairly isolated, but we would be avoiding steep, convex or open slopes in sheltered areas at treeline and below where these layers may be still be preserved and would be ripe for human triggering.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Strong low level southeast winds are a precursor to approaching Arctic air. Tuesday we are back in the deep freeze. Pack your puffy jackets and favourite warm beverages it's gonna be frosty!

Saturday Overnight: The storm will begin to taper in the evening, lighter snowfall will continue overnight with 5-20 cm of accumulation. Winds decreasing to moderate to strong from the southwest. Alpine temperatures around -8 C.

Sunday: Continued snowfall, 5-20 cm of accumulation. Winds shifting southeast in the morning, strong outflow winds expected at all elevations. Temperatures dropping overnight as arctic air repopulates the region. 

Monday: Partially cloudy with light lingering flurries. Moderate to strong southeast winds at all elevations. Temperatures dropping throughout the day, reaching the -20s by the afternoon.

Tuesday: Mainly clear and cold. Alpine temperatures in the -20s with light southeast winds. 

Avalanche Summary

Numerous natural dry loose avalanches up to size 2 where observed throughout the region on Saturday morning, prior to the peak of the storm. 

Natural and human triggered avalanches remain likely today. If you see any avalanche activity, please let us know by filling out a Mountain Information Network report. ?

Snowpack Summary

Yesterday, a significant storm impacted the region bringing upwards of 60 cm of new snow. In open areas, winds created deep deposits of wind slab in lee features. In sheltered areas the new snow formed a touchy storm slab or loose dry avalanche problem. Today, strong southeast outflow winds will create fresh, reactive wind slabs in atypical reverse-loading and cross-loading patterns which could catch riders off guard.

The new snow likely bonded poorly to the old surface, and reactivity may persist into today. The old surface was comprised of hard wind slab, sastrugi, and near surface faceting formed from previous variable winds and two weeks of prolonged cold temperatures. 

Two layers of surface hoar exist within the upper snowpack in protected areas at treeline and below; one is down 40-60 cm (Dec 21) and the other is down 60-100 cm (Dec 18). The distribution of these layers appears to be relatively isolated, but information is limited and there has been very little feedback with recent benign weather pattens.

The early December rain crust is up to 10cm thick, down 80-150cm in the snowpack, and exists to an average of 1400m in elevation. Up to 2mm facets have been reported above this crust, and it is producing hard but sudden planar results in snowpack tests in areas north of Terrace. 

The lower snowpack is well settled, with several decomposing early season crusts. Snowpack depths vary greatly across the region, expect to find anywhere from 140-300 cm of snow around treeline, with highest amounts in coastal areas.

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Be aware of highly variable recent wind loading patterns.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.

Regioni coperte