Long range weather forecast for the Western Isles – 15th 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 Monday 19th April until Wednesday 28th April.

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.

Monday 19th April

Some good model agreement for next Monday. The EC is suggesting some heavy rain moving across the Western Isles with blustery winds. High pressure is expected to move across the entire Western Isles later in the day with winds easing. The GFS also moves in some heavy rain across the Western isles with blustery winds. Also building high pressure across the Western Isles but keeping winds brisk.

Tuesday 20th April

Some slight model differences for next Tuesday as the EC builds high pressure back across Northern Scotland with fine dry and sunny weather. High pressure of 1030 mb. The GFS also builds up high pressure out West in the Atlantic. This would bring in some showers across the Western Isles but things become drier as the day goes on as the high pressure builds further.

Wednesday 21st April

Some good model agreement for next Wednesday. It will be mainly fine and dry according to the EC with high pressure sitting across the UK but sliding out into the North Sea as the day goes on. Plenty of sunshine and variable amounts of cloud. Winds will increase from the South East with brisk winds. The GFS suggests that high pressure will be also in charge but located across the UK and we will see a fine dry day with sunshine and cloud. Lighter winds ehre.

Thursday 22nd April

Good model agreement for next Thursday. The EC suggest that high pressure will build across Norway and we will see fine and dry day with sunshine and cloud. Rain moves west wards towards the UK a fine dry and sunny start to the day before cloud builds in later in the day with brisk winds. The GFS also has high pressure across the UK with brisk winds and plenty of sunshine across the Western Isles cloud increasing later with a risk of some rain moving in.

Friday 23rd April

Some model differences for next Friday. The EC reasserts high pressure across the Western Isles and keeps the rain away. A mainly fine and dry but the cloud is expected to dominate. The GFS instead brings in the rain across the Western isles which would be heavy at times. High pressure declines away.

Saturday 24th April

Some model differences again for next Saturday. High pressure sits to the North East. Low pressure to our South and we are stuck in the middle with a brisk air flow. Sunshine and cloud with a dry day. Winds will be coming from the South East so staying on the cool side. The GFS has a wet start to the day but this rain will clear away to allow for a fine and dry with some prolonged sunshine. Winds will ease.

25th, 26th, 27th and 28th April

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 the first two days of the period will see fine dry and sunny weather with light winds before rain moves in and becoming heavy for the final two days of the the period.

Featured image – Lingay off clachan sands North Uist taken by Cally.

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