Long range weather forecast for the Western Isles – 20th June 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 covering from Thursday 24th June until Saturday 3rd July.

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 24th June

Some good model agreement for next Thursday. Both the EC and the GFS showing low pressure moving away from Scotland and this would bring rain and showers in the morning. High pressure builds behind across the Western isles with sunshine and cloud. The GFS has the cloud breaking quicker with the EC keeping cloud hanging in longer. Winds would also ease.

Friday 25th June

Once again good model support for the weather for next Friday with high pressure across the UK again a day of sunshine and cloud across the Western Isles. The EC once again has more in the way of cloud with a risk of some rain moving in during the late evening. The GFS suggests more in the way of sunshine. Winds would be mainly light.

Saturday 26th June

Further model support for next Saturday. With the both the GFS and EC having high pressure across the UK. A low pressure system clears away from Southern England. For us in the Western Isles we are going to see high pressure dominating. The EC has morning rain clearing away to a mixture of sunshine and cloud. The GFS also has high pressure in charge with cloud increasing as the day goes on with some light rain moving in later in the day but winds being mainly light.

Sunday 27th June

More model support for next Sunday with high pressure across the UK with fine and dry weather from both the GFS and the EC with some decent and prolonged sunshine. The GFS has better support for sunshine. Winds would be brisk. The EC has high pressure to the South West of Ireland and the GFS has high pressure further out in the Atlantic.

Monday 28th June

Some slight model differences for next Monday. The EC has high pressure across the UK but an approaching weather front would bring increasing amounts of cloud across the Western isles with a weather front sitting to the North West of our islands. The GFS has a more brisk airflow from the North West. Mainly fine and dry with sunshine and cloud. A few scattered showers with low pressure between Norway and Shetland.

Tuesday 29th June

Model differences for next Tuesday. The EC brings the above mentioned rain across the Western isles which would be heavy at times. Sunshine and showers into the evening with brisk winds. The GFS on the other had has winds coming down from the North so feeling cooler with sunshine and cloud. Staying dry as high pressure dominates across the UK.

30th June, 1st, 2nd and 3rd July.

Now this is the really long range. So take it with a large amount of salt and is the silly range. So the GFS is suggesting that high pressure would dominate our weather with plenty of sunshine and becoming warmer. Staying on the dry side but this is a long way off as yet so worth keeping an eye on as we get closer to the time.

Our featured photo is Cleat Barra taken by Derek Forsyth

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