Long range weather forecast for the Western Isles – 7th January 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 11th January until Wednesday 20th 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.

Monday 11th January

Good strong model agreement for next Monday between the two main models. We are likely to see rain moving across the Western Isles. This rain will be heavy at times. It will be milder at times with a shallow area of low pressure moves across the Western Isles. High pressure dominates over the Southern half of the UK. We are likely to see brisk winds.

Tuesday 12th January

Some model differences for next Tuesday with the EC bringing spells of rain heavy at time for Uist and Barra it keeps Lewis and Harris mainly dry with occasional spells of rain. Winds will be mainly light. The GFS again brings rain across the Western Isles but this rain would likely be lighter in nature. Brisk winds based on the GFS.

Wednesday 13th January

So model differences for next Wednesday. The EC develops an area of low pressure overnight into Wednesday. This would bring some rain which will be heavy at times. This could possibly bring us some snow. But again there is a lot of uncertainty of that. Stronger winds would also likely be a feature. The GFS doesn’t deepen the low pressure as deeply as th EC but again we are likely to see spells of rain which would be heavy and persistent but this model is not going for snow at this stage.

Thursday 14th January

Quite strong model differences for next Thursday. The EC stalls out the above mentioned low pressure system and it weakens. High pressure very briefly builds in across the Western Isles before towards the end of the day bringing in a deep area of low pressure which could bring a spell of windy weather and heavy rain for a time. The GFS is on the opposite and builds in that high pressure further. If this were to happen we would see fine dry and settled conditions.

Friday 15th January

The EC stalls out the above mentioned area of low pressure across the Western Isles bringing further spells of rain. This would weaken and the rain will clear and high pressure will build in behind it resulting in fine dry and more settled conditions. The GFS brings in a new area of low pressure rather shallow this would bring spells of rain which would be heavy at times.

Saturday 16th January

Good model agreement for a week on Saturday. The areas of low pressure move away. We are likely to see some light rain and drizzle. Lighter winds and high pressure eventually builds in. The GFS has a deepening low pressure system over Ireland.

17th, 18th, 19th, 20th 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 multiple areas of low pressure on the first 3 days. Then possibly turning colder with snow to end the time frame.

Thanks for reading any feedback is always welcomed.

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