White March beckons! Intense cold spell on its way next week…
On several occasions this winter Northern Ireland has experienced cold conditions and snow due to regular incursions of polar maritime airmasses. Cold conditions are now likely to return. This is due to the influence of a Sudden Stratospheric Warning (SSW); this is when the temperature in the stratosphere suddenly rises.
This causes the jet stream to slow/weaken which can lead to cold conditions in the British Isles with an easterly flow.
Prof Adam Scaife explains
A SSW event took place during 12-18 February. There is a lag time between an SSW event and any impact it might deliver to the UK weather.
The weather is set to become progressively colder into the new week as very cold air, with its origins over central Asia / Russia moves into the British Isles. (Extreme sub-zero temperatures seem likely over much of continental Europe from this weekend)
While day-time temperatures will most likely rise above zero through until Tuesday, overnight frosts will become increasingly sharp, especially inland and away from the east coast. By midweek and towards the end of end of next week, temperatures may struggle barely above freezing by day and could drop several degrees below at night. This is likely to result in several days with mean temperatures at or below zero from about Tuesday. Strong east to southeast winds may be a feature at times, making overnight frost more severe.
The combination of low temperatures and wind-chill can have significant impacts on the elderly and those with health complications or the homeless.
The same combination can also have a potentially catastrophic effect on young or newborn livestock in the open.
With such a late season cold spell and winter returning for a few more weeks,– the progress of the new growing season is likely to become retarded and a number of weeks behind normal. (Spring officially doesn’t start until 20th March)
At this range it is difficult to be too precise – but there is an increasing risk of snow, especially across the east of N. Ireland from about Tuesday onwards, probably in the form of showers but heavier, more disruptive snowfall cannot entirely be ruled out at some point between Tuesday and Saturday with the end of next week and the first weekend in March a period which may need to be watched closely.
In the UK, temperatures will struggle to rise above zero in many places from late Monday and the risk of snow increases day on day with the potential for disruptive snowfall in places.