Bollettino valanghe

Maritime

Valdez Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Open full map
Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The avalanche hazard is moderate above 1500'.  Human triggered avalanches are possible up to 2 1/2 feet in depth on recently wind loaded slopes.  The hazard is low below 1500'.  Natural avalanches are unlikely today.

Avalanche forecasts are issued Wednesday-Sunday at 8 am.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    The most likely avalanche problem for a person to encounter today will be wind slabs that formed due to strong southerly winds.  Moderate to strong southerly winds were observed yesterday near Thompson Pass from road level up to high elevation ridges.  These winds were actively forming wind slabs that are expected to be possible for a person to trigger today in specific areas such as cross loaded terrain and the lee side of high elevation ridges and terrain features.  Wind speeds were forecasted to increase along high elevation ridges last night with gusts to 60 mph possible.  With 12-18" of settled storm snow from last weekend expect to find wind slabs up to 2 1/2 feet in depth above 2000'.  Below 2000' a rain crust exists which will limit snow available for transport to a few inches.  

    Terrain that is in close proximity to the Thompson Pass gap will be the most likely area to encounter fresh wind slabs.  As you move South or North from the pass the wind's effect will be less, however, lee slopes just below high elevation ridges are expected to be affected throughout our forecast zone.

    Generally, wind slabs are fairly easy to identify visually and by feel.  Today, they will be more difficult as our area is expecting 6-12 inches of new snow in the next 24 hours, which will mask where these slabs exist.  Winds are forecasted to be lighter but will be blowing in the same direction, which will point you toward where these slabs formed yesterday.  Try to anticipate where these wind slabs exist and avoid areas where they are most likely to be an issue, such as cross-loaded gullies and lee convex terrain.

     

     

    (1/21/2025) Photo: Gareth Brown

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Small storm slabs are expected to begin to form today.  The major issue with the new snow is that it will hide previous wind slab formation near Thompson Pass and also add weight to these slabs that could be sensitive in specific areas.  Shallow new snow instabilities are possible in steep terrain that was previously unaffected by wind, however these are expected to be small and consequences will be determined by the terrain.

    The hazard for this problem will be increasing by tomorrow as snowfall is expected to continue coinciding with rising temperatures.  Expect this problem to jump to the #1 slot at some point in the next 24 hours as wind slabs decrease in sensitivity as they age and storm slabs grow in depth.

    Photo: NWS

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2.5–3.5

    Our snowpack has undergone a major change since the beginning of January.  What began the month as a fairly thin snowpack with very thick vegetation below brushline has trasformed to a thick midwinter snowpack with the alders being mostly buried above 2000'.  Below 2000' the snowpack remains thin.

    This transition is a very welcome sight but it has put significant stress on our snowpack, especially during times of heavy precipitation.  On the 11-12th we received 100" of snow on Thompson Pass in a 48 hour period.  This caused a significant natural avalanche cycle that failed at weak layers in the mid snowpack.  As the new snow was allowed to settle  a much stronger snowpack was observed the following week.  Again on the 19th we received a significant snowfall event with 30" on Thompson Pass in 24 hours.  This produced a few large avalanches (see avalanche tab below bottom line) but was much less significant than the previous cycle.  

    This Natural avalanche pattern along with recent snowpack observations point to the likelihood of triggering a deep slab avalanche being low, but is possible still with a large load or  in steep rocky terrain where storm slabs are thinner.  Large loads would include heavy snowfall events and the days directly proceeding them, cornice fall and large groups.  

    Photo: Gareth Brown

Avalanche Discussion

Observed Avalanche Activity last 72 hours: 

4 Hard slab avalanches occurred at the upper elevations of Mt. Dimond on NE and NW facing ramps on 1/19.

1 storm slab with a very wide propagation occured at upper/mid elevations just north of the Shovel (continental zone). and ran full path.

More info is available about the last avalanche cycle by clicking the Avalanches tab or the Season Summary tab just below the bottom line statement.

Forecast Discussion:

Strong southerly winds formed wind slabs yesterday primarily near Thompson Pass and upper elevations.  These are now being buried by new snowfall which will make them difficult to identify.  Today will be a transition day as winds relax and old wind slabs slowly settle while fresh storm slabs begin to form and will become the main problem potentially by tomorrow.  The freezing line should set up around 500 feet today before shooting back up to 1800 feet by tomorrow.  This will create upside down storm slabs and with up to 2.5" of water in the forecast at upper elevations of the Maritime zone that could translate to 2 feet of snow in the next 48 hours, It will be important to pay attention to new snowfall amounts.  

Last weekend's storm snow has settled to 12-18" inches and what was observed to be slightly top heavy on the 20th, has become more uniform and right side up on the 21st.  Stability tests also point to no major flaws within the snowfall from the 19th or at the interface.

Some large natural avalanches from last weekend point to the potential for deep slab avalanches to occur when a heavy load is applied such as significant snowfall, rising temperatures or cornice fall.  Last weekends natural cycle was much smaller in distribution than the previous week which is encouraging.  Another important point to note is that there were no deep slab avalanches observed in the mid elevations which adds evidence to the idea that persistent weak layers such as the rain crust sandwich that existed at mid elevations was likely flushed out in the 11-12th avalanche cycle.  We are likely going to get another significant test of the snowpack this weekend which will give us some more info.

Additional Information:

A weather and snowpack season history is available by clicking on the Season Summary tab that is located above the bottom line statement once you have entered the full forecast.

Glide cracks that existed on the buttresses from Nicks through Cracked Ice on North aspects at mid elevation were stagnant prior to the recent snowfall and are now filled in.  It will be worth watching for them to reappear, but this may be a problem of the past.

Season Snowfall Data

Location 24 hour Snowfall Inches- 1/18 24 hour Snow Water Equivalent Inches Height of Snow January Snowfall Inches Season Total Snowfall Valdez    Trace    N/O    19     22     45 Thompson Pass    2    N/O   N/O    200    N/O Nicks    3    N/O    110     N/O 46 Mile    0     ~   20    10 N/O

Regioni coperte