Thursday 21st January 2021

So we are back in the cold, and there are more marginal call rain/snow events to provide some forecasting fun. Or forecasting frustration.

Thanks to Paul for the photograph.

This evening starts cloudy, you might just get a splash of rain from a weather front skirting the southern counties of England. Overnight will be clear, breezy with a frost for most, down to around 0’C.

Friday morning will see good spells of sunshine. Some more cloud in the afternoon, one or two scattered showers though many places missing them. 6’C. A chance of a wintry shower in the evening (birthday present for me?), then overnight will be cold and frosty, though a fair amount of high/medium level cloud also. Down to around -2’C, a small chance of some icy patches, and also the odd fog patch by dawn.

Saturday sees low pressure in control to the north-east of the UK, with a cold flow circulating down from the north-west.

Hazy sunshine to start, but as the day goes on there will be more in the way of sunshine, with some fair weather cloud. Cold, 4’C with a small chance of a wintry shower. Clear spells at first overnight with a frost, cloud thickening somewhat later in the night. Down to -3’C – perhaps quite a bit lower in sheltered spots.

Sunday is uncertain, but there is a reasonable suggestion that a trough feature will develop and track east – if it does then I’d fancy it to fall as snow for 1-2 hours – and if it does fall as snow then it should settle, perhaps 1-3cm.

However – it is uncertain, it is a little feature that could very easy track further south than currently suggested, or perhaps have a slight mild core causing it to be rain/sleet, or just not actually develop at all. The slight favourite, is for a short spell of snow, more likely during the morning – but timing is uncertain also.

Otherwise Sunday will be quite cloudy, but often bright with some sunshine. 4’C. Clear spells overnight so frosty, down to around -3’C. Should there be snow cover, it could be a bit colder and ice will be a problem too.

Monday remains cold. It should be dry, with sunny spells and variable amounts of cloud, 4’C. Clear spells at first overnight, frosty, down to around -2’C. High cloud arriving from the west later in the night.

Tuesday sees a start of a change to milder and wetter conditions. Starting bright and cold, cloud will thicken with rain crossing during the afternoon – perhaps a bit of sleet or wet snow to start, but most likely rain. Around 5’C and breezy. Variable cloud overnight, around 6’C.

Wednesday sees the milder, south-westerly flow start to gather more steam.

Fairly cloudy, rain and strong winds arriving at some point – most likely late in the day or evening. 8’C.

Day to day details from here are not possible, but the general pattern will be a mild south-westerly flow, often cloudy, with strong winds and rain at times. It might even reach the giddy heights of 14’C next Friday/Saturday with some very mild air tucked in (perhaps 20’C in Madrid – home of that huge snowstorm the other week).

Most likely it turns colder again after next weekend. And then probably back to mild and wet…then colder…then mild and wet. That kind of switching pattern.

Up in the stratosphere, if you follow me enough, you’ll know that there was a sudden stratospheric warming event on 5th January. They often bring lengthy very cold spells to the UK, roughly from 2-4 weeks after, though not always and the timeline isn’t a set pattern either.

These lengthy very cold spells (ie Beast From The East in 2018) are more likely to happen if the SSW causes the stratospheric polar vortex to split. The SSW from 5th January did not cause it to split – it displaced it and weakened it. Hence no lengthy, very cold spell within the 2-4 weeks since 5th January.

However, models are now suggesting a second SSW event at the end of the month, causing a split. So, cautiously, I’d suggest a lengthy, cold/very cold spell is possible from around the middle of February. Even if the second SSW event doesn’t happen, the original SSW can still influence our weather patterns for possibly some months after, so either way further cold spells are likely in the coming months. And yeah, that includes spring.

Have a good weekend, I will update on Sunday’s snow chances Saturday morning at the latest.

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