Long range weather forecasts

[Helenagrace]

Is there a good long range weather forecast site?

We're off to Cornwall for a fortnight from July 6th and I'm trying to decide if I need to buy extra fleeces and new waterproofs!

Accuweather rather shows a month ahead. July 6th is looking rather nice at the moment

Random 'rather' there

What a brilliant site. We should have planned our BBQ for the day after.

Just because it goes out to that timeframe doesn't mean it is accurate!!

Possibly a bit pointless then?
I could do long range weather forecasts. As long as I didn't say something ridiculous like snow in August, I could charge and arm and a leg.

Hmmm maybe I should just buy new fleeces and waterproofs in the hope that reverse psychology kicks in thereby guaranteeing wall to wall sunshine and soaring temperatures

I wouldn't trust a forecast to make plans to more than 24hours in advance tbh

absolutely rip!!
I think that forecasts out to about 5 days are reasonable - though it depends on the synoptic situation at the time - some weather systems are still very hard to model with any consistency.

What people also need to remember is that there are a fair few different weather models out there and quite often they predict different scenarios. I tend to have most confidence when they are all saying roughly the same thing. Even the same model will give different results depending on the starting conditions fed into it.

Look at GFS ensembles and change the parameter to 'precipitation' or 'Avg Temp' and see how the same model can give different outputs. The closer those outputs are together, the more accurate the forecast is likely to be.