UKC

Understanding Winter Weather With Plas Y Brenin


Overview

Categories:
Winter,
Mountaineering
For safe days in the winter mountains, your two biggest concerns are the weather, and the state of the snow. From interpreting the forecasts at the planning stage, to observations out on the hill, this five-part series from instructor Will Nicholls of Plas y Brenin covers all aspects of winter weather and avalanche forecasts.
In association with Plas y Brenin

Part 1 - How Forecasts Work Together

In part 1, Will looks at the main online forecast services relevant to winter walkers and climbers.


Whether you're out for a day's winter walking, climbing or skiing, the weather and snow conditions will have the greatest impact on your day. Without wanting to sound too melodramatic, paying heed to what's going on around you could be the difference between having a brilliant day out, or having an accident. If you know what you're looking for, you'll be able to adapt your aims for the day accordingly, make the most of the conditions you're working with, and stay safe.

With an eye to the forecasts, we've been able to get out in dreamlike conditions on the Aonach Eagach  © Matt Stygall
With an eye to the forecasts, we've been able to get out in dreamlike conditions on the Aonach Eagach
© Matt Stygall

Every day in the hills starts in the same way for me, whether I'm working or on a day off. I'll check mountain specific weather forecasts and the avalanche forecast. It's useful to see how similar they are: the more similar, the more confident I am in their accuracy. Whether it's wind speed, precipitation, cold temperatures or visibility, the weather on the mountains tends to be more challenging than what is happening in the valley, so getting a mountain forecast is the best thing to do. But most importantly, do remember they're only forecasts – conditions could be very different when you get there!

Less dreamy conditions - but more the norm - on the Douglas Boulder  © Matt Stygall
Less dreamy conditions - but more the norm - on the Douglas Boulder
© Matt Stygall

Here are the key online tools for weather and conditions:

Mountain Weather Information Service

This site offers daily forecasts for the main upland areas in the UK. It looks at various weather data, and then suggests how it'll most likely feel to be out in the hills. It also gives a planning outlook for the whole country, this is well worth a look if you're considering driving to the hills for more than a day or two. New forecasts are issued in the early morning, so you should be able to leave the house with up-to-date information. MWIS also has a very useful twice-weekly video, entitled Latest Forecast Video. It's great for understanding the overall meteorological picture and what to expect each week.

MWIS is one of the primary resources for mountain-specific area forecasts  © MWIS
MWIS is one of the main resources for mountain-specific area forecasts in the UK
Met Office Mountain Weather

This is similar to the MWIS forecast, but doesn't offer a long term mountain forecast. I find the predictions to be really accurate, but the descriptions can sometimes be a little baffling. It might be easier to look at the numbers rather than the text. A note at the top of the page gives the meteorologists' assessment of their level of confidence for the forecast which is a nice feature. It also gives the times for sunrise and sunset, so you'll know how many hours of daylight to expect. These forecasts are updated every morning.

The other primary resource is the Met Office mountain forecast  © Met Office
The other primary resource for weather is the Met Office mountain forecast

The Met Office also provide summit forecasts for popular mountains. Just type the name of the mountain you're interested in, followed by Met Office Summit Forecast into a search engine and click the link. This is a fantastic resource, as it breaks the day into hourly segments. It's really easy to see the change in wind strength, direction, summit temperature and chance of precipitation. I use this a lot. The accuracy is generally very good, I'd expect it to be correct to within an hour normally.

Windy

This is a cool site if you respond better to graphics than text. It makes it easy to see where our weather comes from, and how it changes through the course of the day.

Windy gives a nice, animated, big picture view  © Windy.com
Windy gives a nice, animated, big picture view

Yr.no

This Norwegian weather site seems to work well wherever you are in the world. My only criticism would be to say that the amount of precipitation is often overestimated. If you're on a ski trip and looking forward to a day of waist deep powder, you may find it's 'only' shin deep! A great resource.

It's a really useful source of reference, and good worldwide not just in the UK  © YR.no
It's a really useful source of reference, and good worldwide not just in the UK
© YR.no

SAIS

Last, but by no means least, the Scottish Avalanche Information Service is a vital source of info if you're heading to the Scottish mountains in snowy conditions.

SAIS area map  © SAIS
With six forecast regions, and loads of detail, SAIS is an essential winter tool

SAIS contains all the info you need for the planning stage of a safe day out on the winter hills. Six forecast regions in highland Scotland are updated on a daily basis throughout the winter season. The avalanche forecasters create a forecast for the following day, note their observations of that day, and generally update a daily blog with photos too. We will cover avalanche forecasts in a lot more detail later in this series.

As we descend it warms up, and snow turns to sleet... but we were expecting that, thanks to the forecasts  © Matt Stygall
As we descend it warms up, and snow turns to sleet... but we were expecting that, thanks to the forecasts
© Matt Stygall

  • Part two of the series will consider what to look for in the weather forecast

Plas y Brenin logo  © Plas y Brenin

All Plas y Brenin winter courses cover in detail the topics described in this series. Attending a course is probably the best way to develop the skills and understanding you'd want to head out in winter independently.

www.pyb.co.uk

If you'd like to learn more about getting out in winter, Plas y Brenin are running a series of webinar sessions designed to give you the skills you need, and the majority of them are free to attend. Head over to www.pyb.co.uk/events to see what's on and register now.

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