A ‘seasonable’ January chill: Assessing the UK snow threat this week

Written by on January 21, 2019 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Well it’s safe to say the cold which was expected to intensify this week into the upcoming weekend is not going to show and in fact it turns milder not colder by Friday. On a plus, it’s a temporary push of mild.

The reason? That storm system exiting Canada has not forced sharp height rises over the Atlantic into Iceland so therefore NW rather than NE winds affect the UK bringing a chilly polar maritime rather than continental air in.

Note the below chart and the lack of amplification to our west. The flatter ridge (due to Iceland low) simply rolls over and not north of the UK Friday but once this moves through and the low’s CF clears, we’re back in the NW polar maritime flow.

Credit: wxcharts.eu


Credit: wxcharts.eu


Credit: wxcharts.eu

In terms of snowfall, well this looks to be sporadic in the form of convective showers blowing in on a brisk NW flow. The cold front travelling SE over the UK tonight will have mainly low level rain and high ground snow on it but colder air shall follow and IF enough cold air gets drawn in, we could see coverings of snow even to low levels over Northern Ireland, Republic, Scotland, England and Wales either by morning or during the day tomorrow.

High ground above 800ft should see pre frontal snow as well as snow on the rear.

Credit: wxcharts.eu

However, notice the GFS indicates a sharp turn over to snow in the wake of the front over Highland Scotland but this progresses south with potentially a few inches fall above 500ft, perhaps coverings to near sea level.

Credit: wxcharts.eu

Credit: wxcharts.eu

As the precip band moves into SE England, colder air over the continent may help turn rain to snow and so London and SE England should be watched for even some low level coverings by tomorrow morning. If it doesn’t occur on the English side of the channel, we should see it even on the beaches of France, Belgium and Netherlands.

Credit: wxcharts.eu

GFS snow depth as of 2100 Tuesday.

Credit: wxcharts.eu

As we head into mid week, high pressure settles things down but with cold air in place, expect hard overnight frosts which struggle to lift during the day. Coldest so far for the UK is -10.8C and this could be beaten with fresh snow, light wind and clear sky Tuesday and or Wednesday night.

As warmer Atlantic air moves in later Thursday, so the snow cover gets wiped out.

Credit: wxcharts.eu

So the polar maritime returns this weekend and it looks to remain cold through next week.

The AO is undoubtedly negative but the NAO refuses to go negative. This has thrown a spanner in the works but is it a complete surprise? No and even though it’s struggling to go negative currently, there’s no reason to think it won’t or can’t towards the close of the month and during February. The models continue to see lows tracking from Iceland towards France with building heights over the Atlantic towards Iceland later next week. Will wait with anticipation…

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