• The Chatel Snow Report

30/11/2018: Today's Updates... 6.10pm...


6.10pm:

So far this evening, the optimistic trend from the models for the period from about a week's time is continuing with some OK scenarios being produced from the 2 GFS runs since our morning update. There is still plenty that can go wrong with the potential evolution, however, if these positive trends continue through the weekend, then we could be in business!


As far as the weather goes this evening, we currently have rain falling in the village.

Will update if this turns to snow before 9pm.



4.10pm:

The clouds have thickened this afternoon bringing some light rain to the village with some light snow falling a short distance up the mountain. A trail run in the Barbossine area this afternoon found the flakes were falling above about 1350m/1400m. This page will be updated during the evening, when we may see a few flakes in the village and there will also be another quick look at the latest models.


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10.30am: It remains cloudy and overcast here in Chatel this morning, no precipitation yet.


Below are a few frames from this morning's models, the GFS, UK Met Office and ECMWF, all from the excellent meteociel.fr website. These are the model's operational runs (or deterministic as they are also known) and form the basis of the automated apps and websites that you may use. For example, the GFS operational run powers sites such as SnowForecast .com, whist the ECMWF powers one of the popular Norwegian sites. Meteo France use their own models with some input from the ECMWF. A glance at the 144hr time frame below shows how these models can show really quite different evolutions, meaning their value when used on their own is limited.


This is the reason why you will often see some really significant differences showing on the automated sites - eg all those huge amounts of snow showing 5 days away on some of the GFS sites, which end up being hopelessly wrong. To be fair, it is not these sites, or the models fault that they can be incredibly unreliable just a few days ahead, it is simply that the weather in this part of the globe is incredibly complex and difficult to model more than a few days out. Added to this is the issue that forecasting precipitation is difficult and it is only the really hi-res models that run at much shorter timeframes, that can provide a more realistic estimate - and even they can be very wrong!


Professional meteorological agencies have access to other models that are not available to the general public, including decider products, which guide forecasters to the likelihood of a particular solution. We don't have access to such things, so rely on the operational models, their ensembles (which are a number of separate runs of the same model, run at different resolutions), and any hints we can glean from the output of the professional agencies.


So, when is it going to snow properly?


As hinted at yesterday, there are signs of a change at the back end of next week.


A glance again at the charts below show low pressure affecting the UK in the early hours of Wednesday morning and then there is that divergence mentioned above, at 144hrs, with the UKMO model showing pressure building over the UK. From that point onwards, it is really very difficult to know what comes next, however, the GFS and ECMWF models do suggest low pressure playing a role again. Note that on the 192hr ECMWF chart, low pressure is set up in what appears to be a very favourable position, firing in an increasingly cold and snowy northwesterly feed, and the final image below, way out at 216 hours, shows the wintry outcome, with cold air from a northerly quarter engulfing our region. The GFS evolution is not as favourable at this stage.


What these ECMWF charts do bring is hope, as although when treated in isolation they cannot be trusted, they do show that there is a potential way forward to the area seeing some genuine cold and snow. On the converse side, other scenarios, potentially less favourable, resulting from different evolutions, are perhaps equally possible, so at this stage it is a case of seeing promising signs, without getting too excited.


We'll be keeping a close eye on this over the coming days.


Chart from the excellent meteociel.fr website



7.55am: Bonjour!

The forecast page was updated a few minutes ago and despite the short term disappointment which is still on the way (Sunday / Monday - eek!!!), there is still some reason for optimism for the period from a week's time. In the last few minutes, the ECMWF model has produced perhaps the best chart of the winter season so far, which we'll have a look at during the morning - probably before 10am.


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