Uncertainty. Uncertainty is a word forecasters use a lot when it comes to long range forecasting but at the moment it seems things are more uncertain than they usually would be.
Above are the latest outputs from the ECM model and the GFS model for Thursday next week.
The ECM has high pressure ridging North-Eastwards to the North of the UK and this allows low pressure over Europe to align towards the UK sending the coldest air towards us.
The GFS on the other hand has high pressure sinking South-Eastwards across the UK and this sends the coldest air through France and South-Westwards towards Spain. With two models showing very different weather for the UK it’s incredibly difficult to get an idea of what the weather will do.
The reason? A snow storm across the Eastern Seaboard of the United States, a Nor’Easter. The GFS pushes this storm out into the Atlantic much faster than the ECM which flattens the downstream pattern.
With such discrepancy between the two big models it’s next to impossible to forecast the weather beyond Tuesday at the moment. Two solutions;
- High pressure builds North-Eastwards and we see very cold air move across the UK. This option would have the greatest risk of bringing widespread snowfall.
- High pressure sinks over the UK sending the cold air to our South. Temperatures would still be below average but the risk of widespread snowfall would be significantly reduced.
The two options are finely balanced at the moment, though we think the ECM colder option is slightly more favoured because it tends to handle low pressure systems across the US a little better than the GFS.
The first risk of snow comes tomorrow (Friday) as a weather front pushes in across Western parts of the UK. Wales and North-West England at particular risk of seeing some snowfall with local accumulations of 2-4cm. It will be patchy and tend to fizzle out as it slides away South-Eastwards.
Tuesday brings perhaps a wider risk of snow. A trough disrupting through the UK into cold air will turn to snow across Northern and Central parts. There is huge uncertainty regarding timing/intensity/extent of snowfall so we can’t go into detail about this at this stage but it’s something we’re keeping an eye on.
Beyond that, temperatures likely to remain below average for the foreseeable but how cold? That’s the big question and one that we hope to be able to answer very soon!