How to interpret our Avalanche Bulletins

Wednesday, 12 December 2018

For the past 6 seasons we have been summarising the daily avalanche bulletin for Chamonix and then sharing it on Social Media (primarily Twitter). Due to mainly using Twitter we have limited characters for what can be a complex explanation of the risks, and hence we have to abbreviate at times. The good news is that Twitter now has increased characters, so we can make them a bit longer. However, we still want to be concise where we can, so we wanted to explain some of our common abbreviations to you.

Perhaps the easiest way to do this is to use a real example, so we will add a Tweet of the forecast for tomorrow (Thursday 13 Dec 2018) and then explain what it all means.

"ChxAv13Dec 3/5. Slab in recent blown snow. notably at alt >2200m. Also, note weak layer >2400m from old snow in Nov W/N/E asps. Sponts unlikely, small slides pos around rocks through heating. 1900-2000m cracks may form on sunny steeps"

Translation: Chamonix Avalanche Bulletin 13 December 3/5 (Level 3 out of a max of 5). Windslab is likely in recently windblown snow, especially at altitudes over 2200. There is also a weak layer above 2400m caused by the old snow that fell in November on West/North/Easterly aspects. Spontaneous avalanches are unlikely, but small slides may occur around rocky outcrops due to solar activity. Around 1900-2000m glide cracks may form on very steep slopes in the sun.

Other abbreviations that may be used include:

3/5-4/5. A changing level of danger, where the day will start at one level but change to another. In this case, increasing risk from 3/5 to 4/5.
^ This symbol also denotes increasing (risk or amounts of wind/snow)
< This symbol denotes "below" eg High Risk <2000m.
alt = altitude
Pack = Snowpack
Temps = Temperatures
pm = afternoon
Cat = Category eg Cat 5 (The highest level of avalanche risk)
Esp = Especially
N/S/E/W = Cardinal Points of the compass. NE/SE etc are also used to denote aspects.

PLEASE REMEMBER THAT IT IS ALWAYS BETTER TO READ THE FULL REPORT VIA THE METEO FRANCE WEBSITE OR APP (METEOSKI). Our summaries are an aid. They are not a replacement for a detailed forecast. The bulletins are published daily, in French. If you don't yet follow us, the we are @AvalancheAcad on Twitter.