Long range weather forecast for the Western Isles – 18th April 2021

Good afternoon and welcome to our long range forecast. This is posted either once or twice a week covering from 4 days ahead to 10 days ahead. In this update coving from Thursday 22nd April until Saturday 1st May

Please note there is not a lot of accuracy for this kind of time frame. Anything beyond 4/5 days out becomes really difficult and subject to change so we will be looking at trends. Mainly take with a large vat of salt. We will be using the main two computer models for this. The ECMWF ( European Centre for medium range weather forecasts) which is based in Reading and the GFS (Global forecasting system) which is the American based global model.

This comes from the GFS 06z run and ECMWF 00Z run. I will refer to EC to save on typing.

Thursday 22nd April

Good model agreement for next Thursday. High pressure is firmly in charge of the weather across the UK. The EC keeps high pressure over Northern Scotland. We would see a mainly fine and dry day with sunshine and cloud along with light winds. The GFS has high pressure in the North Sea. Light winds with some decent and prolonged sunshine and variable amounts of cloud and light winds.

Friday 23rd April

Some more model agreement for next Friday. The EC keeps high pressure across the UK with low pressure to the South West of the UK. We would see a fine and dry day with sunshine and cloud. Light winds. It would feel quite mild with winds coming from the East. The GFS bring the low pressure system closer to the UK but still keeps it to the South West. With some showers moving into England and Wales. For us in the Western Isles we would see fine and dry conditions with sunshine and cloud. Slightly stronger winds then the EC is showing.

Saturday 24th April

Some slight model differences with the EC suggesting high pressure remains in control of the weather across the UK. A day of sunshine and cloud. Light winds. The GFS moves the area of low pressure across Ireland. For us in the Western Isles things would stay fine and dry. But we are likely to see overcast conditions with brisk winds. Staying on the mild side.

Sunday 25th April

Some model contrasts for next Sunday. The EC builds high pressure to the North West of Scotland. This would allow a colder airflow to set up. A few wintry showers could move down the North East coast of Scotland ( I know ) for us in the islands. Fine dry and sunny conditions with breezy conditions with cooler air coming down from the North. The GFS keeps the slow moving low South of Ireland which would bring rain and showers across England and Wales. Another fine and dry day across the Western Isles. A slight risk of some showers later in the evening.

Monday 26th April

Some slight model differences for next Monday. The EC suggests that the above mentioned high pressure system slides further South it will bring with it colder air with the risk of some rain and showers across the Western Isles with a day of sunshine and showers. The GFS keeps high pressure in charge with a day of brisk winds and sunshine and cloud.

Tuesday 27th April

Some differences once again for next Tuesday. The EC has a cold airflow across the UK. Rain and showers moving across the islands and these will be heavy at times. A brisk winds will also set up. The GFS on the other hand has a slack airflow setting up with rain and showers. Some sunshine and breezy conditions.

28th, 29th, 30th April and 1st May

Now this is the really long range. So take it with a large amount of salt and is the silly range. So with the GFS it suggests that conditions will turn more unsettled with rain and showers. These would be heavy at times with low pressure dominating the weather across the UK.

Featured image – Grimshader taken by Carol Macdonald.

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