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Snow forecasting tools

Quick guide to snow forecasting


06/11/2021

Forecasting the exact date when snow will fall?

Unfortunately making reliable and accurate snow forecasts in the UK is very difficult. Conditions are often very marginal and even at short timescales computer models and forecasters can be caught out. But here on the website you'll find some of the very best tools freely available in the UK to help out in your quest. 

You can of course stick to using the UK postcode or location 16 day and hourly weather forecasts. They can be selected at the top of this page. However, if you would like to dig a little deeper to understand more about the likelihood of snow arriving in the short to medium term this brief guide has been put together for you!    

Sunrise on a snowy day in  Berkhamsted

It arrived this time but forecasting when it will snow is difficult

14 day instant snow forecast

The easiest and quickest way to check the daily probability is to use our new Will it snow? feature. It combines data from several different computer models to give a percentage chance of snow falling on a given day for up to two weeks ahead. Just enter your UK location, postcode or use one of the direct UK cities links. 

The forecasts update four times each day. 

When to use

These are best used when quickly looking for medium range guidance.

16 day probability forecasts

Whilst Will it snow? is a great way of checking the latest outlook you may want to delve into the matter in a little more detail. If that is the case then the next stop is the 16 day probability forecasts. They use data from the GEFS ensemble model and update four times each day.  

Three charts are displayed. Key in the winter months is the one showing 850hPa (approximately 1500m above sea level) temperature and rainfall. As a very approximate guide, 850hPa temperatures of -10C or lower will usually produce very cold conditions in the UK. So this chart is also one of the best to help identify whether snow will be arriving as part of a  prolonged and deep freeze or just a transient cold snap. 

On the plot look at how many of the individual lines dip below the -10C level and how long they stay there. In total 33 lines are plotted with each representing one individual run in the model. If a very cold spell is imminent there is a good chance that an increasing number of the runs will be dropping below the -10C level.

The other key indicator on this chart is the snow row. It highlights how many runs in the model are forecasting snow to fall on each of the coming 16 days. The maximum number it can take is 33 which would mean that all of the runs are forecasting at least a few flakes of snow. 

When to use

These are best used when looking for medium range guidance.

GEFS London example chart
GEFS example chart showing upper air temperatures, precipitation and snow row

Snow row tracker

You use the GEFS snow row feature to track the values from successive runs for a range of locations. The page by default displays the snow row values from the latest run for the next 16 days. You can also display the snow row scores run by run for the last month and the daily totals for the last 12 months. 

When to use

This can be very useful to see if the GEFS is trending away or towards a snowy outlook.

Ensemble forecast charts

An ensemble model is one which is run multiple times with the starting conditions tweaked slightly on each instance to help account for uncertainty and to assess the probability of a particular outcome.  

Postage stamp chart show the forecast from all of the individual runs in the ensemble model at a given time. These are very helpful to determine where snow is likely (or not) to fall.

NCEP GEFS ensemble

GEFS postage stamps go out to 16 days ahead. Select the UK snow and date options to display the snow forecasts from all of the runs in the model.

UK Met Office MOGREPS-G ensemble

Snow depth and snow rate charts generated using data from the UK Met Office's MOGREPS-G ensemble are available on the MOGREPS-G chart viewer. The charts go out to 198 hours ahead and the data can be displayed either in postage stamp or line graph format.

When to use

These can be used to provide medium and short range range guidance. In particular the MOGREPS-G charts are very useful for helping to determine the amounts of snow that is likely to fall.   

MOGREPS snow rate forecast example
MOGREPs-G example chart showing forecast snow rates

UK Met Office UKV model

The UKV precipitation type and snow depth charts are generated using data from the UK Met Office's UKV model. This has a very high resolution so it can identify local differences much better than the longer range global models.

Updates are made available twice each day and go out to 120 hours ahead.    

When to use

This is one of the best tools on the site to look at when snow is a realistic possibility in the next few days. It is particularly good at helping to identify local variations.

Other tools

There is a range of other tools available on the site to help in your search to find snow. The best place to start is the Model inventory where you can select from a massive and growing range of computer forecast charts and data. 

A word of caution

Please remember that despite providing a wealth of data from many of the best computer models in the world things can and do go wrong. Local variations can be big and even high resolution models may not accurately represent them.

The chaotic nature of the weather combined with the UK's geographical location makes snow forecasting particularly difficult. Therefore, it is wise to treat forecasts of the exact date when snow will fall with a big dose of salt; even more so when they are many days or weeks ahead. You will probably be able to produce more accurate forecasts for yourself by investing a little time in learning to use the tools discussed in this guide.

 

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