Haute-Tarentaise
4 – HighSource: Météo-France
This is an AI-generated translation and summary. It may contain errors. Always read the full official Météo-France avalanche bulletin before any mountain activity.
Risk Level: 4 - High
Title: VERY UNSTABLE SNOWPACK: NUMEROUS SLABS REMAIN VERY REACTIVE. WITH DAYTIME WARMING, NUMEROUS NATURAL RELEASES IN MID-MOUNTAIN AREAS.
Description:
VERY UNSTABLE SNOWPACK: NUMEROUS SLABS REMAIN VERY REACTIVE. WITH DAYTIME WARMING, NUMEROUS NATURAL RELEASES IN MID-MOUNTAIN AREAS.
Issuance of a special avalanche bulletin (CSA).
Triggered avalanches: numerous slabs remain very sensitive to the passage of a single skier. North-westerly winds have contributed and continue to form these slabs, which are crumbly at the base and foot of slopes, sometimes with few visual clues. They are occasionally hard when approaching ridges where the wind has been locally very strong (especially in the Val d'Isère sector). Given the heavy recent snow accumulation, fracture lines can be very thick, generally resulting in size 2 (medium) avalanches. These slabs are found on all aspects, primarily above 2000-2200m.
An aggravating factor: above 2000m on cold aspects (East/North/West), and even on South aspects at high altitudes, persistent weak layers buried within the snowpack may still react to a skier's passage or trigger in a cascade following an initial slab release: these result in larger and wider avalanches (size 3).
Spontaneous releases: with the return of the sun and relative warming (0°C isotherm around 2000m in the afternoon), we expect:
(1) On all aspects below 1800-2300m, numerous glide-snow slabs and slope slides, especially on steep, grassy slopes. Since snow depths are significant even at these mid-altitudes (100-150 cm), the volumes involved are substantial, and the resulting size 1 to 2 avalanches could affect high-altitude roads or parking lots.
(2) On South aspects up to high altitudes, some point-release avalanches in fresh snow as it becomes moist. Generally size 1 (small) to 2, but an exceptional size 3 avalanche involving a buried persistent weak layer in a cascade is not ruled out.
Risk Level: 4 - High (Travel in avalanche terrain is not recommended. Large natural avalanches are likely, and human-triggered avalanches are very likely.)
Title: VERY UNSTABLE SNOWPACK: NUMEROUS SLABS (layers of bonded snow sitting on a weaker layer) REMAIN VERY REACTIVE (easy to trigger). WITH DAYTIME WARMING (rising temperatures), NUMEROUS NATURAL RELEASES (avalanches starting on their own) IN MID-MOUNTAIN AREAS.
Description:
Triggered avalanches (caused by a person): many slabs remain very sensitive to a single skier's weight. North-west winds have created "wind slabs" (accumulations of snow blown by the wind), which are crumbly/soft at the bottom of slopes and can be hard to see (few visual clues). Near ridges, these slabs are harder/denser due to stronger winds. Because of the heavy recent snowfall, the "crown" or fracture line (the top edge where the snow breaks away) can be very deep, typically causing Size 2 avalanches (large enough to bury or kill a person). These slabs exist on all sides of the mountain (all aspects), mostly above 2000-2200m.
A dangerous aggravating factor: above 2000m on cold-facing slopes (East/North/West) and even South-facing slopes at high altitudes, there are persistent weak layers (hidden, fragile snow crystals like sugar or frost) buried deep down. These can break under a skier's weight or cause a "cascade effect" (a small slide triggering a much larger, deeper layer), resulting in Size 3 avalanches (large enough to destroy a car or small building).
Spontaneous/Natural releases (starting without human help): as the sun comes out and it gets warmer (the 0°C isotherm—the altitude where it stops freezing—rises to 2000m), expect:
- Glide-snow slabs (the entire snowpack sliding off the ground like a rug) on all sides of the mountain below 1800-2300m, especially on steep grass. Because the snow is deep (100-150cm), these involve a lot of snow and could hit roads or parking lots (Size 1 to 2).
- Point-release avalanches (loose snow starting from a single point) on South-facing slopes as the sun warms the fresh snow. These are mostly Size 1 (small) or Size 2, but there is a rare chance of a Size 3 if a deep weak layer gets involved in a chain reaction.
| French | Translation & Notes |
|---|---|
| MANTEAU NEIGEUX TRÈS INSTABLE : NOMBREUSES PLAQUES ENCORE TRÈS RÉACTIVES. | Very unstable snowpack: numerous slabs still very reactive. Manteau neigeux is the technical term for snowpack. Plaques (slabs) refers to a cohesive layer of snow. Réactives means they are easy to trigger. |
| AVEC LE REDOUX EN JOURNÉE, NOMBREUX DÉPARTS NATURELS EN MOYENNE MONTAGNE. | With daytime warming, numerous natural releases in mid-mountain areas. Redoux indicates a rise in temperature after a cold spell. Départs naturels are avalanches that occur without human intervention. Moyenne montagne generally refers to elevations between 1500m and 2500m. |
| Émission d'un communiqué spécial avalanches (CSA). | Issuance of a special avalanche bulletin (CSA). A CSA is an official alert issued by Météo-France when avalanche conditions are particularly critical or unusual. |
| Déclenchements provoqués : nombreuses plaques encore très sensibles au passage d'un skieur. | Triggered releases: numerous slabs still very sensitive to the passage of a skier. Déclenchements provoqués means avalanches caused by a person or animal. Sensibles highlights that even low pressure (one skier) can trigger the slab. |
| Le vent de nord-ouest a contribué et continue à former ces plaques, friables en pied et bas de pentes avec parfois peu d'indices visuels. | The north-west wind has contributed and continues to form these slabs, which are crumbly at the foot and base of slopes, sometimes with few visual clues. Friables describes soft or uncompacted snow that still behaves as a slab. Indices visuels (visual clues) like wind-scoured snow or drifts are often missing here, making them harder to spot. |
| Elles sont parfois dures en approchant des crêtes où le vent a localement été très fort (surtout secteur Val d'Isère). | They are sometimes hard when approaching ridges where the wind has been locally very strong (especially in the Val d'Isère sector). Crêtes means ridges. Wind-hardened slabs are denser and often more bridgeable but can release more violently. |
| Au vu des forts cumuls de neige récente, les cassures peuvent être très épaisses donnant généralement des avalanches de taille 2 (moyennes). | Given the heavy recent snow accumulation, fracture lines can be very thick, generally resulting in size 2 (medium) avalanches. Cumuls refers to total accumulated snowfall. Cassures (fractures/crowns) are the vertical walls at the top of a slab release. |
| On retrouve ces plaques en tous versants, plutôt au-dessus de 2000/2200 m. | These slabs are found on all aspects, mostly above 2000/2200 m. Tous versants (all aspects) means the danger isn't limited to a specific compass direction (North, South, etc.). |
| Facteur aggravant, au-dessus de 2000 m et en versants froids (Est/Nord/Ouest), et même en Sud à haute altitude, les couches fragiles persistantes enfouies dans le manteau pourront encore réagir au passage d'un skieur ou en cascade à la suite d'une première plaque : elles engendrent alors de plus grandes et larges avalanches (taille 3). | Aggravating factor: above 2000 m on cold aspects (East/North/West), and even on South aspects at high altitude, persistent weak layers buried in the snowpack may still react to a skier's passage or in a cascade following an initial slab: they then generate larger and wider avalanches (size 3). Couches fragiles persistantes (Persistent Weak Layers or PWL) are dangerous because they stay active for weeks. En cascade refers to a 'step-down' avalanche where a small surface slide triggers a deeper, larger layer. |
| Départs spontanés : avec le retour du soleil et le redoux relatif (isotherme 0 °C vers 2000 m l'après-midi), on s'attend à : | Spontaneous releases: with the return of the sun and relative warming (0°C isotherm around 2000 m in the afternoon), we expect: Départs spontanés is another term for natural releases. Isotherme 0 °C is the altitude at which the temperature is zero degrees Celsius. |
| (1) En tous versants sous 1800/2300 m, nombreuses plaques de fond et glissements de talus, surtout dans les pentes raides et herbeuses. | (1) On all aspects below 1800/2300 m, numerous glide-snow slabs and slope slides, especially on steep and grassy slopes. Plaques de fond (glide slabs) are when the entire snowpack slides on the ground. Pentes herbeuses (grassy slopes) are notorious for this because grass acts as a slippery lubricant when wet. |
| Les épaisseurs de neige étant notables dès ces moyennes altitudes (100-150 cm), les volumes mobilisés sont conséquents et les avalanches de taille 1 à 2 ainsi engendrées pourraient concerner les routes ou parkings d'altitude. | Since snow depths are notable even at these mid-altitudes (100-150 cm), the volumes involved are substantial, and the size 1 to 2 avalanches thus generated could affect high-altitude roads or parking lots. Volumes mobilisés refers to the amount of snow moving in the avalanche. |
| (2) En Sud jusqu'à haute altitude, quelques départs ponctuels dans la neige fraîche s'humidifiant. | (2) On South aspects up to high altitudes, a few point-release avalanches in the fresh snow becoming moist. Départs ponctuels are loose-snow avalanches (sluffs) that start from a single point, usually in wet or very light snow. S'humidifiant means the snow is getting wet/heavy from heat. |
| Généralement des tailles 1 (petites) à 2, mais une exceptionnelle avalanche de taille 3 mobilisant en cascade la couche fragile persistante enfouie n'est pas exclue. | Generally size 1 (small) to 2, but an exceptional size 3 avalanche involving the buried persistent weak layer in a cascade is not ruled out. N'est pas exclue is the forecaster's way of saying it is possible even if not the most likely scenario. |
| French Term | English Term | Definition |
|---|---|---|
| Manteau neigeux | Snowpack | The total layers of snow on the ground. |
| Plaque | Slab | A cohesive layer of snow that can break away from the layers beneath it. Includes 'wind slabs' and 'glide slabs'. |
| Réactive | Reactive / Sensitive | Easily triggered by a person or natural forces. |
| Redoux | Warming / Thaw | A rise in temperature that often weakens the snowpack by introducing liquid water. |
| Départs naturels | Natural releases | Avalanches that occur without any human or animal trigger, usually due to weather changes like sun or rain. |
| Moyenne montagne | Mid-mountain | Lower-elevation mountain zones, typically below the high alpine and often below the treeline. |
| CSA (Communiqué Spécial Avalanches) | Special Avalanche Bulletin | An emergency alert issued for extreme avalanche danger or unusual conditions. |
| Déclenchements provoqués | Human-triggered / Triggered releases | Avalanches caused by the weight of a person (skier, walker) or a machine. |
| Couche fragile persistante | Persistent Weak Layer (PWL) | A layer of snow (like depth hoar or buried surface hoar) that remains fragile for a long time and is difficult to detect. |
| En cascade | Step-down / Cascade effect | When an initial avalanche triggers a deeper, larger layer of snow, making the slide much bigger. |
| Isotherme 0 °C | Freezing level / 0°C Isotherm | The altitude at which the temperature is exactly 0°C. Above this, water freezes; below it, it melts. |
| Plaque de fond | Glide slab | A slab of snow, often the entire snowpack, that slides off the ground surface (often grass or rock). |
| Départ ponctuel | Point release / Loose snow avalanche | An avalanche that starts at a single point and spreads out in a triangular shape; common in wet snow. |
| Taille 1 | Size 1 | Small avalanche; unlikely to bury a person, though there is a risk of falling. Can travel 10-30 meters. |
| Taille 2 | Size 2 | Medium avalanche; large enough to bury, injure, or kill a person. Typically stops on the slope. |
| Taille 3 | Size 3 | Large avalanche; can bury and destroy a car, damage a small building, or break trees. Can travel to the bottom of the valley. |
| Versant | Aspect / Slope | The compass direction a slope faces (e.g., North aspect). |
| Risk level 4 | High Danger | The second-highest level on the European avalanche scale. Conditions are very dangerous; triggered avalanches are very likely and large natural ones are expected. |
Download the original Météo-France bulletin in French (PDF).
Download original PDF (French)