25 Jan 2013

Rain, gales and flood risk into next week

The cold spell that has been with us for the past fortnight is going to come to an end this weekend, as mild air eventually spreads in from the Atlantic – marking the beginning of the big thaw.

However, before the thaw begins, there’s going to be one last heavy snowfall during Friday afternoon into the early hours of Saturday morning.

This is because a band of rain moving in from the west will collide with the cold air across us, readily turning to snow – especially across north east Wales and Scotland, as well as central, eastern and northern parts of England.

Here, as much as 5-10cm could fall at lower levels, with 10-20cm possible over the hills and mountains, drifting around in a strong southerly wind.

The main risk of disruption later this afternoon and overnight is likely to arise from the fact that the snow will be heavy and wet, with large flakes. This kind of snow can accumulate very quickly, resulting in road conditions deteriorating fast, catching drivers out.

Also, heavy wet snow combined with strong winds can cause ice to form on power lines, with the possibility that they may snap under the weight of ice, leading to power cuts.

The band of rain, sleet and snow will clear the east coast early on Saturday morning, leaving behind a significant ice risk as temperatures hover around 0C.

Weekend thaw begins

Whilst there’ll be some wintry showers affecting Scotland for a time on Saturday, most of the UK will be dry with some sunshine.

For southern and western areas, any lying snow will begin to thaw, as temperatures reach 3-6C. Elsewhere, it’ll be another cold day with highs of 0-3C and a thaw only starting to happen in low lying areas.

The real push of mild air will arrive during Saturday night into Sunday, when temperatures for many places will reach 3-8C. Combined with heavy rain, this will increase the rate at which any lying snow melts.

Rain, gales and flood risk next week

The weather during next week looks very unsettled, thanks to an active jet stream roaring to life across the Atlantic – sometimes reaching a speed of 200mph.

This will result in a succession of deep areas of low pressure arriving on our shores as the week progresses, bringing heavy rain, mild air and strong winds.

With the ground still relatively saturated following December’s flooding, the combination of heavy rain and snow melt could renew the flood risk, as two sources of water flow into our river catchments at the same time.

In fact, the weather computer models are suggesting that by the middle of next week, Wales and western parts of England and Scotland could have 40-70mm of rain, with more than 100-120mm over the hills and mountains.

The latest Environment Agency three day flood risk forecast has Wales along with northern and western parts of England at a low risk of river and surface water flooding this weekend. However, with more rain to come next week, the flood risk could increase.

Don’t forget, you can get the latest five day forecast on the Channel 4 Weather website or follow my updates on Twitter – @liamdutton

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