For the model watchers out there, you probably spat your tea over your keyboard when you saw the 6z GFS come through today which brought a rather interesting low pressure system across the UK and Ireland next Wednesday with some colder air wrapped around the Northern edge of it.
In fact, for the 12z GFS run today, the same feature also seems to crop up. We mentioned a few days ago that when you get a long fetch of cold air such as this across the Atlantic then it's not usual to see disturbances running through them, in fact, it's more unusual to see a 1,000 mile cold fetch with nothing in it than not.
We have an advance weather warning out for the colder air which is expected to reach the UK from Monday. But, and this is the important bit... Disturbances within cold fetches like this are notoriously difficult to predict. In fact, the system on Wednesday is just the models way of getting a little itchy with some disturbance and developing it into a notable system. It could stay as a wave, it could move further South, it might not even develop.
So, take this output at the moment with a load of gritting salt (which may also come in handy next week) as this isn't a model weakness, but it's something which happens with numerical models a few days out and something meteorologists shouldn't take too seriously until it falls within the 3-4 day time frame.
If it is still there in the model runs on Sunday in the same way that it's been in the model runs today then you can expect a heads up form all agencies, but at the moment if you do have any travel plans next Wednesday/Thursday then just keep an eye on forecasts over the next few days. Nothing set in stone, but just something which we are monitoring with the latest output at the moment.
METEOROLOGIST : MARSH
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