Long range weather forecast for the Western Isles – 25th 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 29th April until Saturday 8th 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 29th April

Some good model agreement from both the GFS and EC. They show high pressure across the UK but a slack airflow. For us in the Western Isles it would be a day of sunshine and cloud. A few scattered showers and these would be heavy a times. Winds coming in from the North East and it would be a brisk wind. On the cool side.

Friday 30th April

Again good model agreement for next Friday. The EC has high pressure over much of the UK. A slack airflow with sunshine and showers. Some of these falling as sleet and snow over higher ground of Scotland. For us in the Western Isles a cool feeling day with sunshine and showers. These heavy at times and a brisk wind. More of the same for the GFS a weak area of low pressure over Ireland. Sunshine and scattered showers across the Western Isles. Brisk winds and feeling cool.

Saturday 1st May

Again similar model agreement for next Saturday. Both the EC and the GFS has high pressure over most of the UK and low pressure over ireland. For us in the Western Isles we will see brisk winds again. Sunshine and cloud. Now it will still be feeling cold with a risk of some frost and ice during the early hours. (Yes I know in May).

Sunday 2nd May

Some model differences for next Sunday with the EC suggesting we will see rain and showers across Scotland. With low pressure out West. A day of sunshine and showers for us in the Western Isles and a brisk wind. The GFS has low pressure off the coast of Ireland bringing rain to much of the Southern half of the UK. For us in the Western Isles with sunshine and cloud and breezy conditions.

Monday 3rd May

Some big model differences next Monday. The EC brings a deep area of low pressure into Western Scotland. This would bring spells of rain heavy at times and blustery winds. Turning to sleet and snow over mainland Scotland. The GFS keeps low pressure close to Ireland. A fine and dry settled conditions across the Western Isles with sunshine and cloud. Feeling cold in a Northerly wind.

Tuesday 4th May

Some model agreement for next Tuesday. According to the EC the low pressure system moves slowly into the North Sea. At first we could see rain and then behind it colder air with sleet and snow showers possible. The GFS also suggesting a cold airflow with sleet and snow showers moving down from the North with a brisk airflow. The risk of frost and ice. A long way off as yet so plenty of uncertainty. I will keep you posted.

5th, 6th, 7th and 8th 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 a cold spell with more sleet and snow showers moving in for the first two days. A cold wind with the next area of low pressure moving in later in the time frame.

Featured photo – West Tarbert. Taken by Kirsty Young

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