We are accustomed to think that weather forecasts exist to make our lives just more convenient: We take an umbrella with us when it is going to rain, and we don't go out with a coat when it is going to be a hot day; however, weather forecasting is far more important for the safety of any sort of outdoor activity.
Some weeks ago I was, along with some other people from Andinia.com about a hundred kilometres away from the now active Chaiten volcano; this mountain remained inactive for about six thousand years and a few months ago began erupting again. We were in the area for two reasons: One, it was interesting to go there again to take a look from a safe distance, and then, we, the partners of Andinia.com had our annual meeting there. It is customary for us to make such meetings in open spaces because we loath any sort of corporate offices for such ends. For us, dealing with the great outdoors, it seems most fit to do our meetings outside.
A hundred kilometres is a reasonably safe distance to stare at an active volcano in almost all cases; however, geologically and geographically speaking, such a distance is a mere speck. It is plausible that the activity at Chaiten is exerting some sort of influence in the local weather systems and transforming its patterns. The fact is that the volcano has been inactive for more than sixty centuries and now, the local storms that developed and particularly the winds that we observed were second to none.
I can't say this with scientific certainty now, but the coincidence between the change in weather factors and the activity of the volcano seems striking. In all my years in the region and the many expeditions in which I have encountered many different weather conditions, I have never seen or experienced winds like those found there this year. Before this, no wind threatened to lift me from the ground carrying a 40 kg backpack with me, and this is no exaggeration but exactly what happened: Wind gusts were at times so intense that if you were not in some sort of shelter, in order to literally stay put where you were, you had to take cover much like when someone is shooting at you with a machine gun. Small stones went flying too, like bullets. But once you hit the ground, you had to grasp something like a rock or use your piolet because if not, you would feel like slippering over the terrain as the wind forced you to move, even in horizontal, flat areas.
This real-life event should remind everyone that weather forecasting and an understanding of the basics of meteorology are fundamental survival skills too: The mountains in the area produced more fatal victims this summer than ever. However, since we know the area because we are locals and we always go to the mountains, we avoided the winds by staying inside improvised shelters most of the time. However, at some moments it became necessary to go outside and confront the winds.
So, now that you see what can happen, you have to take into account three fundamental rules of mountain weather:
Local weather systems usually form independently from regional ones: You can have a rather nice weather in a broad area, but every valley and peak can easily develop its own, local conditions that can differ profoundly from the general picture. So, while the county or province where you are might be experiencing fair weather, the valley where you are trekking or the wall where you are climbing could easily get bad weather, like if it were developed just for you.
Weather changes usually very fast: It is difficult to make reliable forecasts at the local level, and for all practical effects, trekkers, navigators in lakes and mountain pilots should assume that half an hour is the time frame in which the conditions that they are experiencing might change radically. This means that if you see that the weather conditions are worsening, you shouldn't assume that you will have until the next day or so: Always assume that in thirty minutes things could go very wrong and you will have to take immediate action.
Seasons are not determinant: In the mountains you can experience rather warm days during the winter and even hot days with a snow covered landscape, or you could get a blizzard during the summer. While such conditions tend to change rapidly - i.e. summer snow usually melts within a day - they could compromise your safety if you are not careful. You don't need the time span of a polar winter to get frostbitten or suffer hypothermia, but at most, a few hours.
This doesn't mean that you shouldn't go to the mountains, but treat them with due respect and act conservatively. Minimalistic concepts like ultralight hiking or climbing, meaning that people carry the less possible gear, is of no use in mountainous regions, even in the case of well-seasoned people:
Winter and bad weather gear are a necessity.
You should carry your rainproof and cold-weather gear in a way that makes it immediately accessible. If you are in the open and you find out that you need to disembowel your whole backpack to reach your raincoat or poncho; that would betray its whole purpose.
Place all the gear that you plan to take with you in plastic or waterproof bags. That would give your staff an additional layer of protection.
Always opt for the worst-case scenario in your decisions: If rain is likely, assume that it will become a fact.
A typical worsening scenario; notice the effect of the wind on the lake. Less than half an hour later it begain raining heavily and winds surpassed 100 km/h by an ample margin.