/ How to read & understand weather forecasts for winter climbing

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JonmapDL - on 30 Dec 2012
Given all the rightful intrigue and chat around 'conditions', and the obvious importance of understanding these... am depressingly aware of the shallowness of my understanding here. Thought it'd be helpful for all if we shared some wisdom on wat winter climbers should be looking out for in forecasts before we set off... both in terms of safety and enjoyment.

most basically, have found these websites helpful:
avalanche info here: http://www.sais.gov.uk/ (Also recommend the MCofS/glenmore avalanche awareness course)
General mountain weather forecasts here: http://www.mwis.org.uk/
Here's a helpful UKC logbook for recent ascents and comments: http://www.ukclimbing.com/logbook/winter.html

Any tips on what to look out for in these?
Milesy - on 30 Dec 2012
Checking the avalanche forecast should be religious. Take care on slope aspects with warnings in particular gullies, hollows and open slopes.

Weather in terms of climbing conditions. Look for the freezing point listed and look at the height of where you want to climb. If freezing level is above your climb or "above summits" then things will be melting.

Fresh snow fall will mean potentially avalanche risk, but also that approaches to climbs and the climbs might be swimming in useless powder snow. Good for skiing and boarding but not climbing.

After freezing levels rise and things start to melt you want a freeze again to form ice and solidify the snow into what we call neve. Which is hard frozen snow. It can take some large thaws and freezes to do this or several smaller cycles.

So if you look at the next few days as freezing level above summits and the a day forecast for freezing level down to 600m or 800 or even ground level you want to get out and see what has survived and what has formed.
ice.solo - on 31 Dec 2012
In reply to Milesy:

All good stuff.

Id include looking at the orientation of your area of interest too, ie north/south sides of valleys, direction of gullies, proximity to bodies of water. All of which help or hinder.

Ground formation too has much to do with it regarding cooling rates and saturation. What freezes well in one instance melts fast in another.

Then, get any local data possible. Many forecasts work off digital models and can be very wrong. Japan has very predictable conditions in most areas but ive seen freeze levels out by 1000m.
Britain, with its topography, geology, altitudes and off shore currents...good luck. I spent a winter there a while back and felt it took either an obsession, a gift or the toss of a coin
Andy Nisbet - on 31 Dec 2012
In reply to JonmapDL:

If you're like me, get up at 5am, then look at the summit temperatures on Cairn Gorm (plus 2 degrees) and Aonach Mor (plus 3 degrees), look at the rainfall radar (heavy rain) then go back to bed. Changes of plan are worthwhile (I hope).
James Thacker - on 31 Dec 2012
In reply to JonmapDL: An old link but this might be of some use: http://blog.jamesthacker.co.uk/2011/11/scottish-winter-tactics.html

There are a couple of references to some good information on 'conditions' in Martin Morans book and by Andy Nisbet/Rab Anderson in Scottish Winter Climbs by the SMC.

Summit temperatures of Aonach Mor and Cairngorms are really useful. Best thing I think is to try and interpret synoptic charts yourself then look at MWIS and Met Office. The '528' Surface Thickness line appearing on a synoptic is a give away to cold conditions...

Also http://www.wetterzentrale.de/pics/avnpanel1.html - although I have just noticed it looks warm for a while...! Argh

drmarten on 31 Dec 2012
In reply to JonmapDL:
From synoptic charts you can gauge wind direction and speed, frontal passage and presence or otherwise of colder air. Continued studying of forecasts against actual reports will allow you to make a judgement on whose forecasts tend to be accurate and whose are occasionally exaggerated. Get to know which temperature at the roadside means it's unlikely to be worth getting out the car to head for the foot of a climb. There are other local factors that come with experience. Put it all together and after several years you may call it wrong slightly less than you would do now. Multiple early morning drives and walks into dark windy, avalanche prone or stripped corries in the rain will increase your ability to call it off the night before.
JonmapDL - on 31 Dec 2012
In reply to Andy Nisbet:
> (In reply to JonmapDL)
>
> If you're like me, get up at 5am, then look at the summit temperatures on Cairn Gorm (plus 2 degrees) and Aonach Mor (plus 3 degrees)


Thanks Andy, so just to clarify - you'd avoid the norries with a +2oC cairngorm summit because it means a warm crag (~+4-7ish?)... and that's too high a temperature to climb on?

What sort of temperature bracket are we looking for?
JonmapDL - on 31 Dec 2012
In reply to JonmapDL: Thanks all - really helpful stuff. Here's another good website for norries climbers.
http://saisncairngorms.blogspot.co.uk/
Taurig - on 31 Dec 2012
In reply to James Thacker:

> Also http://www.wetterzentrale.de/pics/avnpanel1.html - although I have just noticed it looks warm for a while...! Argh

Thanks for the link, that's useful. Just wondering though, I'm guessing the temperatures on the charts (-30 etc.) are at fairly high altitude, any thoughts on what temperature over Scotland means freezing level at sea level, 1000m or whatever?
Andy Nisbet - on 31 Dec 2012
In reply to JonmapDL:

I meant that I had actually got up this morning (hence the post at 6am) and decided to go back to bed. It really needs to be minus 2 or lower on Cairn Gorm first thing, as it will likely warm up. The crag in Coire an Lochain might be one degree warmer than the summit, Sneachda two degrees warmer. My general rule of thiumb is that if it's 7 degrees at sea-level (which happens to coincide with seeing your breath), then climbing will be fine, if it's 8 degrees then borderline and if it's 9 degrees then thawing and no good. This is Nov to Feb. Once you get into March and April, the sun can increase the temperature and it still be freezing on the crags. If the wind is very light, then other factors come in to play and are less easy to read, like temperature inversions and latent heat. I haven't really thought much about this for years, as now you can look up MWIS and it tells you.
Orgsm on 31 Dec 2012
In reply to JonmapDL:

You'll find the sais application a really useful refresher for assessing routes and avalanch conditions

http://www.glenmorelodge.org.uk/avalanche.asp

Available for mac or pc
Orgsm on 31 Dec 2012
In reply to A Game of Chance:

Sorry glen more lodge application
Tim Davies - on 01 Jan 2013
In reply to JonmapDL:

Start to understand lapse rates. Moist air can mean almost no temperature change with altitude, but I've seen 12 degrees in April in Fort Billy and it' was Baltic on the Ben- cold, dry easterly air.
Connected with the above, look for the source of the airmass- this week the air is warm and moist, coming straight from the Azores. This air is slowly cooled and becomes more humid (grey, damp weather on the hills)

528 thickness contour a handy tool as already mentioned.

Also look for ridges of high pressure and troughs of low pressure giving extremes of good/ bad weather.

Jim Fraser - on 02 Jan 2013
In reply to JonmapDL:

The big picture is usually apparent from a study of air masses. It's about more than an east wind. You have to understand what is next in the chain and therefore what the east wind will carry towards you.

Conditions for snow evolve depending upon the temperature and density of particular layers in the atmosphere. Forecasts of the thickness of the layers and the temperature of particular pressure levels is available on specialist websites.
Joak - on 02 Jan 2013
In reply to Jim Fraser: Used synoptic charts for yonks, 20 years ago did my RYA Yachtmasters ticket (theory only, didnae require the wearing of yellow wellies!!) primarily for the met paper, pre internet, listening to recorded shipping forecasts and plotting your own isobar chart linking the equal pressure figures. Only discovered the 528 thickness contour in this thread!!
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Jim Fraser - on 03 Jan 2013
In reply to Joak:
> (In reply to Jim Fraser) ... did my RYA Yachtmasters ticket (theory only, didnae require the wearing of yellow wellies!!) ...

Aye, well if it snows in Hamble then as you ski across the glacier 1000m above the Northern Corries you'll be more worried about the polar bears than the weather.

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