Weather Alert: Heavy rain, snow and risk of avalanche

From Thursday November 30 at 12:00 to Friday December 1 at 9:00.

Complete live weather forecasts by telephone at

3201*

Situation

A new depression is positioned this Thursday off the coast of Brittany. It brings with it a very active rainy front from the southwest to the Alps. The rain/snow limit rises in the Alps to around 1700 to 2000 meters depending on the massifs, causing washout below these altitudes. The associated heavy rains, combined with the melting of the snow, are causing river reactions and the risk of overflowing on Friday. At altitude, wet snow between 1700 and 2500 meters destabilizes the snowpack, hence the risk of avalanches becoming significant this Thursday evening.

Observation

This Thursday

At 15h, the accumulations now reach 80 mm in Vaujany (Isère), 70 mm in Ornon (Isère), 55 mm in Novel (Haute-Savoie) and 54 mm in Flaine. The rain and snow limit is generally between 1800 and 2200 meters depending on the mountain range.

At 12we noted 66 mm in Vaujany (Isère), 60 mm in Ornon (Isère), 49 mm in Villar-Loubière (Hautes-Alpes), 41 mm in Flaine (Haute-Savoie) and Saint-Sorlin d’Arves (Savoie). )

At 9 o’clock, with the rapid warm spell underway, the rain/snow limit is now around 1200 meters in the Alps. In Chamonix, rain replaces snow and melting begins. Further north, it snows lightly from 1000 m on the Jura to 400 m in the south of Alsace where the cold air is more resistant.

At 6 a.m., the disturbance arrived in the middle of the night in the center-east with often sustained rain, particularly on the western slopes of the relief. Snow falls around 850 to 1200 meters in the Alps, while very temporarily snow is observed from 300 to 500 meters in the south of the Vosges and the Jura, which whitens the soil.
This morning, we measured 5 cm of fresh snow in Chamonix (74) since yesterday evening and 12 cm in Tignes (73).

Evolution

This afternoon, the rain/snow limit tends to rise above 500 meters from Lorraine to Alsace, while the rains remain very marked from Jura to the Alps with accumulations becoming significant and rivers starting to react well. the risk of avalanche becomes marked on the alpine relief between 1700 and 2500 meters.

This evening and this night, with the shift of the wind to the northeast sector, the snow drops again to the plain in the northeast. Falls are generally low, but soils may turn white due to nighttime cooling. The rains remain heavy in the Jura and the Alps, even if at the end of the night, they end up losing intensity. The rain/snow limit drops to around 1000 meters in the Jura at the end of the night and 1300 to 1500 meters in the Alps.

Friday morning, It continues to snow lightly in the plains from Lorraine to Alsace where a small layer on the ground has formed. Light to moderate rain persists over the Alps and the snow gradually decreases towards 1200 meters over the Alps. We fear the reaction of watercourses in the Alpine valleys with possible overflows in places. The risk of avalanches will remain very high throughout the Alps.

On the episode we expect:

– 50 to 80 mm of rain in the Jura and Alpine departments by Friday morning, locally more than 100 mm (evening 2 to 3 weeks of rain in 36 hours)
– 15 to 20 cm of snow on average between 1700 and 2000 m on the Alpine terrain
– 20 to 50 cm beyond 2000 meters and more than 80 cm beyond 3000 meters.
– a marked avalanche risk across all Alpine departments on alert

List of departments concerned

  • 01 -Ain

    Precipitation – Significant Risk

  • 04 – Alpes de Haute Provence

    Precipitation – Significant Risk

    Snow – Significant Risk

    Avalanche – Significant Risk

  • 05 – High mountains

    Precipitation – Orange Alert

    Snow – Significant Risk

    Avalanche – Significant Risk

  • 25 – Doubs

    Precipitation – Significant Risk

  • 38 – Isère

    Precipitation – Orange Alert

    Snow – Significant Risk

    Avalanche – Significant Risk

  • 39 – Jura

    Precipitation – Significant Risk

  • 68 – Haut-Rhin

    Snow – Significant Risk

  • 73 – Savoy

    Precipitation – Orange Alert

    Snow – Significant Risk

    Avalanche – Significant Risk

  • 74 – Haute-Savoie

    Precipitation – Orange Alert

    Snow – Significant Risk

    Avalanche – Significant Risk

  • 90 – Territory of Belfort

    Snow – Significant Risk

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