Long range weather forecast for the Western Isles – 20th December 2020

Good evening 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 24th December until Saturday 2nd January.

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 which is based in Reading and the GFS 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 December

Strong model agreement for next Thursday with high pressure in place to the South West of the UK. This will bring spells of rain across the islands but becoming drier later. We could see some wintry showers first thing. Brisk winds and feeling cold with colder air sitting across the Western Isles.

Friday 25th December

Good model agreement once again with high pressure declining away. We are going to see a brisk airflow. Showery to start with and then we will see rain move in later in the day. Temps will start off cold but will become milder as the day goes on heading towards double figures. It will be a fairly windy day with winds gusting 30 to 40 mph.

Saturday 26th December

Some model agreements for Boxing day. The EC is showing heavy rain across the islands for most of the day. A chance some of this rain could turn wintry. Staying fairly windy with winds gusting 30 to 40 mph. The GFS also shows rain moving across the islands. Heavy at times. It also introduces snow showers across the islands to end the day. A lot of uncertainty about that as yet but worth keeping an eye on.

Sunday 27th December

Good model agreement for next Sunday. We are going to see cold air across the islands. We are going to see wintry showers and spells of rain moving across the islands. These heavy at times with sleet and snow mixed in. Along with brisk winds. Again some uncertainty on the snow amounts.

Monday 28th December

Some model agreement with both models showing cold air streaming across the islands from the North. The EC has a stronger airflow with wintry showers moving down and brisk winds. The GFS slackens the airflow somewhat compared to the EC with further wintry sleet and snow showers with rain at times. A low pressure sits out in the North Sea.

Tuesday 29th December

Some model differences here. The EC continues to highlight a cold airflow streaming across the islands with further wintry showers and rain at times and brisk winds. The GFS however cuts off the supply of cold air down from the North as high pressure builds in from the West. A lot of uncertainty at this time frame though.

30th, 31st December, 1st and 2nd January

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 suggests that we are going to see a dry day for the 30th. Wintry showers for the final day of the year and low pressure and rain for the New Year.

Thanks for reading any feedback is always welcomed.

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