So I have looked at the Fax charts and the Compare charts so I know what the air masses are doing and I have a good understanding whether I am under high pressure or low pressure and what systems are starting to encroach into my area and whether there are frontal systems associated with it. And most importantly it gives me a clue to wind direction I can expect, if I know the wind direction I know what sort of weather is associated with wind from that direction.
So now I go down to the drop down menu and select the UK wind speed/direction chart to take a closer look at the winds and advance the chart through the hours I am interested in. Wind info gives me a lot of information. If winds are moving away from in different directions I know that air is sinking and if it is sinking it is not going to rain and the sky is going to be clear. If winds are converging then the air is rising, convection is happening, I will see cumulus cloud and other convective cloud, I can expect convective showers or thundery showers and if the conditions are right thunder storms or even worse. In winter this convergence may lead to snow showers.
Next I look at temperature, This gives me some idea of what kit I will need, if I am on a multi-day trip I am normally more interested in temperature during the night time hours because I want to select kit that best suits the conditions, I am mainly a hammock user these days and temperature is the main concern when swinging.
Next I might look at precipitation as most people think this is important. Rain for me is an inconvenience. However during winter there are some additional precipitation charts, snow risk and precipitation type which try to predict chance of snow and if it precipitation is rain, sleet or snow. These are useful as a guide only snow forecasting is difficult at best.
One chart that is very useful is the ‘Height of the 0° isotherm’. As a guide snow starts to melt once it has fallen through 600’/182 m of air above freezing so if the 0° isotherm is within 182 meters of ground level then the chance that precipitation is going to snow is high.
Finally during the warmer months (all year round for me) I check the UK CAPE & Lift Index chart to see how strong rising air is rising, As mentioned above rising air is convective and convective air can lead to thundery showers, thunder storms and worse.
If you are interested in cloud cover I suggest you look at satellite images which are freely available on the net.
As I said before forecasting at this level is not an art it is a case of interpretation of the data available. We can take it back further, right back to raw data if you are truly interested but that takes a lot of time to understand and more time to forecast, we are only interested in what weather we can expect on our trip.
Please remember we do not have crystal balls, the models are exactly that, models they do not predict the future so the charts should not be taken as 100% accurate.
If you want to make a quick check of what is going to happen over the next couple of hours whilst you are out it is worth just checking a rain radar
http://www.raintoday.co.uk/ this will show you what is heading your way.