Roughly 10 days till Christmas now so we are going to increase the frequency of our white Christmas forecast to every 2nd day right up until Christmas eve. We are still using the GFS model which covers Christmas Day. The ECMWF covers till the 23rd. The ECMWF stands for the European Centre for Medium Range Weather Forecasts.
So we are still a long way off for Christmas. 10 days out there is plenty of uncertainty. There is still a trend towards colder conditions.
The most recent run of the GFS the 06z suggests high pressure to the West of the UK this would bring an North Westerly airflow across the Western Isles. This would mean squally wintry showers across the Islands. So we could see some sleet and snow but this would not mean widespread snow.
The 00z run from the early this morning suggests a Northerly airflow again with high pressure to our West but a little closer. This would bring a greater risk of sleet and snow showers across the Islands.
The 18z model run also has high pressure further West again covering the Western Isles. This would result in fine dry and settled conditions for Christmas day.
So the positives are that we are still trending colder for Christmas but again far to early for any certainty. A lot of it will depend on low pressure system tracks.
So based on the latest model run information and the trends at this stage I am going to go for a 65% chance of Western Isles White Christmas.
Next update will be on Wednesday evening.