Snow expected to cause disruption in parts of West

Parts of the West - especially across Gloucestershire - are likely to see snow developing later on Saturday, with disruption possible

Snow and ice look set to cause disruption in parts of the West this weekend.

A Met Office yellow warning, covering all but the far south of the region, comes into force at midday on Saturday.

On Friday the Met Office issued an amber warning for snow and ice, covering all of Gloucestershire and northwards into the Midlands, which starts from 18:00 GMT on Saturday.

Snow will turn to rain as the evening unfolds but the rate at which this happens will vary from south to north.

Snow will persist for longer in northern parts of the region, especially across the Cotswolds.

Where snow will fall is uncertain

Met Office warnings for snow and ice, Saturday afternoon onwards into Sunday: The yellow one is in force from 1200 GMT on Saturday; the amber one from 1800 GMT

The forecast is a classically awkward one for this region, with milder air following from the south west causing initial snow to change to sleet, then rain.

Key uncertainties in this region are multi-fold - the main one is just where snow will first start to appear.

Some forecast computer models indicate this happening across central parts of Somerset during the mid-afternoon and onwards, with the snow risk then quickly spreading northwards up to Gloucestershire into the evening and at least initially into the night.

Conversely however, other models are much less bullish.

With the exception of highest ground - for example the Quantocks, or Mendip plateau - these other simulations foresee mostly rain falling anywhere south of about Bristol, with snow only starting to appear from around the M4 northwards.

So for certain, this will be a tricky forecast in terms of local detail and emphasis.

Nonetheless, for all our areas broadly north of Bristol the risk of snow is considerably higher and the Met Office amber warning reflects that likelihood.

Small margins of distance, elevation and timing will be crucial as to whether rain or snow falls by late Saturday for anywhere broadly south of the M4

Freezing rain an added risk

The Met Office amber warning makes specific reference to a risk of "freezing rain".

This is a very specific meteorological phenomenon but rare here - and thankfully so.

Where it occurs, freezing rain is especially treacherous.

Raindrops literally freeze instantly on contact with any surfaces - be that pavements, roads, car windscreens, power lines, parked aircraft, or whatever else.

Consequently, ice risks become especially profound and very dangerous.

By Sunday morning, milder air will have spread north across the entire region and the snow risk will have completely gone.

For Somerset, Wiltshire and Bristol the snow - where it has fallen - will likely have changed quite quickly to rain through the latter stages of Saturday.

But for those in Gloucestershire, especially the Cotswolds and Forest of Dean, the transition away from snow and associated ice risks will take longer.

Please keep across the weather warnings, as further revisions between now and Sunday remain possible.