The weather is chaotic and Britain has some of the most changeable weather in the world. Mountainous areas are subject to this change more than other areas and the Yorkshire Dales is no different.
If you're visiting the Dales for a general day out then a forecast obtained via newspapers, radio or television is probably sufficient. If you are going biking, climbing or hill walking then you will want a more detailed forecast and if you're going caving then you'll need as much reliable weather information as possible. Currently websites provide the most up-to date, convenient and useful method of getting a forecast.
The answer is: more than one!
A forecast is basically comprised of weather data collected at various sites, a computer to model the dynamics of the atmosphere and the physical processes that occur, an interpretation of this model to finally produce a weather forecast in a relatively simple format. This is never going to be 100% accurate, it's just too complicated and the weather is too changeable.
During a spell of settled weather it doesn't really matter which forecaster you use but during changeable weather or in marginal conditions, comparing forecasts from different providers will give you a more reliable consensus. By using different forecasts we partially overcome errors in data, models and forecasters.
The key is to use services that uses different modelling and forecasters from each other. For example, BBC weather currently uses Meteo Group as their forecaster so if you use these two services then you're basically getting the same forecast.
The services I currently use are listed later but between them they have detailed forecasts, rain radars and pressure charts and have proven to be reliable. They also provide good mobile phone apps.
The honest answer is that I don't know. By using different services that use different models and forecasters you are hopefully answering this question. Weather prediction is incredibly difficult, the amount of data involved is staggering. For example, read this from a Guardian article in 2018:
"If the number of grains of sand on Earth’s beaches is, according to one estimate, 7.5 x 1018 – or seven quintillion, five hundred quadrillion – then by 2020 there will be one bit of weather and climate research stored on the Met Office’s new supercomputer for each grain, or 1.2 exabytes of it, according to David Underwood, the Met Office’s deputy director of high-performance computers."
It is important to remember that a forecast is just that: an informed guess, albeit a very well informed, hi-tech guess.
The Met Office claim that their "four day forecast is now as accurate as our one day forecast was 30 years ago" and "that 92% of the Met Office’s next day temperature forecasts are accurate within 2 degree C and 91% of the Met Office’s next day wind speed forecasts are correct within 5 knots."
Your first step in getting a forecast on a website or app is to probably input a location. This sounds simple but when using a website, one crucial step is to check the location of the forecast, especially when your forecast is delivered without a map. For example, if you want a forecast for Ingleton because you are going caving down Tatham Wife Hole then the Met Office app provides two locations. The Ingleton near Durham won't be much use to you in North Yorkshire! The Meteo Group app lists these two locations as Ingleton, Carnforth and Ingleton, Darlington. And yr.no provides Ingletons all over the world.
The second part of using the correct location relates to height. A forecast for Ingleton isn't the same as a forecast for the summit of Ingleborough. Many websites now allow you to select mountain summits.
It's easy to complain about the forecast being wrong but this is usually due to the high chaotic, complex nature of the weather and expecting an accurate forecast too far ahead. According to the Met Office, if you want detailed, local weather then don't look further than one to two days. To really pinpoint localised weather, such as where showers will occur, then the timeframe is shorter.
Three to five days ahead is a general picture for a region and six to fifteen is a broad description for the UK.
Don't expect an accurate forecast too far out and check it regularly.
It sounds simple but one way to improve the forecast is to look at all the detail. The symbols that are displayed describe the predominant weather for that period. So a sunny interval symbol doesn't mean it's not going to rain, it just means that the chances of rain are small over that period. Many forecasters now include a "percentage chance of precipitation" value which I feel is crucial in reading the forecast accurately. A 20% chance coupled with our sunny intervals symbol tells you a bit more than just the symbol alone.
When the forecast is split up hourly, it's important to remember that the forecast for say 0900 takes into account the forecast for an hour either side to allow for variations in timing.
What does the weather forecast symbol mean to you? One man's sunny intervals is someone else's cloudy day.
Many forecasters also provide a "feels like" temperature to take into account wind chill. Obviously this can be crucial to days on a mountain.
Finally, when was the forecast updated? A forecast that was updated a few hours ago is obviously more accurate than yesterdays forecast.
I currently use the Met Office, Meteo Group and yr.no. I generally check the Met Office first and if conditions look changeable (they provide a percentage reliability) I then check Meteo Group and yr.no. Hopefully between the three there is some form of consensus! I also use the Mountain Weather Information Service , especially for days out in the Lakes or Scotland, and Windy when I need a beautiful pressure or rainfall map.
The website provides everything you need. As well as forecasts (hourly for the first two days and including a "percentage chance of preciption" and "feels like" temperature), you can access forecasts for mountain summits, a mountain weather forecast, rain radar, weather maps, surface pressure maps and a weather warning service which can be accessed through various channels, personally I use the email alerts. They also include forecasts for wind (speed, gusts and direction), sunrise and sunset, UV, air pollution, pressure, humidity and visibility. The android app also has all these features except the mountain weather forecast and the rain radar, I assume the Iphone app is similar.
The Meteo Group has a very handy rain radar called Rain Today
Caving requires a bit more information than just a forecast, especially for deep, flood prone caves. This information can be split into three requirements: previous weather, current weather and forecast weather.
The next step is to check recent rainfall to get an idea of ground water levels. The rainfall radar on the Met Office website provides the last 6 hours of data and the MeteoGroup provides 2 hours. MyLocalWeather provides data for various timescales and is particularly useful because you know exactly where each station is. This is my personal choice.
The Cave Diving Group checks water levels every day at various locations.
Current weather
The final step is to check the forecast was correct and to see what the weather is doing now. MyLocalWeather is not a forecast, it tells you exactly what is happening now. This is useful even if you are in the area because the weather can differ between Dales.
The importance of choosing the right location
At a basic level, there's often more than one location with the same name. Make sure you have the correct one.
If you're visiting Ingleton and walking up Ingleborough get a forecast for both locations, they could be significantly different due to the elevation change. Many weather forecast sites allow you to get a forecast for mountain summits.
The Enviroment Agency monitors rivers levels at various locations.