TRENDS for the week of 19 to 25 Dec 2020
-- Temperatures will average near normal or slightly below in parts of the east.
-- Rainfall will average 50 to 75 per cent of normal values.
-- Sunshine may manage to exceed the late December average by 25 to 50 per cent.
FORECASTS
TODAY will be partly cloudy with passing showers, some of them quite heavy especially in west Munster where they could be prolonged with hail and thunder possible. Rather blustery southwest winds at times, 50 to 80 km/hr. Highest temperatures around 9 or 10 C.
TONIGHT will see these showers beginning to die out gradually, with some clear intervals. If you have clear skies around sunset, check out the view of the Jupiter-Saturn conjunction which is almost at its closest point (low in the southwest). The overnight lows will be 3 to 6 C.
SUNDAY will continue a bit unsettled but with fewer and less intense showers generally, and some longer dry intervals may develop around mid-day. Highs near 8 C.
SUNDAY NIGHT into early MONDAY, rain and moderate south to southwest winds will sweep in as the remnants of the U.S. northeast snowstorm arrive, but all of the cold air that had to work with is no longer available, so it will be just a rain event in Ireland, with winds southwest 60 to 100 km/hr at times, temperatures peaking around 11 C in the early morning hours of Monday. Later on MONDAY, partly cloudy, breezy to windy, with passing showers and falling temperatures, reaching about 7 C in the afternoon.
TUESDAY will be a bright and cool day in the north, could turn overcast again in the south as a weaker component of the Atlantic disturbance moves by to the south, but there could be intervals of sleety light rain near the south coast, with temperatures in the range of 1 to 5 C in most places during the day.
WEDNESDAY will become breezy to windy and quite cold with mixed wintry showers likely, winds northwest to north at about 50-70 km/hr adding a chill to daytime readings only 3 to 6 C.
THURSDAY (24th) will continue bright and cold with bands of wintry showers expected near some coasts in moderate to strong northerly winds at times reaching 50 to 80 km/hr. Lows near -1 C and highs 5 to 7 C.
FRIDAY (Christmas Day) will have a frosty start in parts of the east and inland south, where morning lows could drop to -4 C. Variable amounts of cloud will follow, with isolated wintry showers possible but rather limited to high terrain in the north mainly. A rather strong westerly wind will develop later in the day pushing temperatures slowly back up towards 7 or 8 C in the evening hours. Light rain could develop near Atlantic coasts overnight into the 26th.
On the 26th and 27th weekend, it appears likely to be rather mild and quite windy as the colder spell from the north starts assembling itself over far northern latitudes and strengthens the frontal boundary between the arctic air and the milder Atlantic flow which will keep trying to maintain control over most of Ireland and Britain. This may persist even into the 28th according to some guidance, although there is still a fairly high chance that the colder turn will arrive on the 27th and deepen on the 28th. Eventually, the colder air seems almost certain to break through and dominate for a time around New Years, and some of the charts near the end of the model guidance (into early January) make it look like a battleground scenario will follow, where the Atlantic tries to push back at the cold air and runs into resistance, the result of which on past occasions (like New Years of 1979) has been a fairly significant snowfall across large parts of Britain and Ireland. So while there may be small amounts of snow at first with the colder spell expected just before New Years, there is the potential for larger amounts in January, word to the wise, be ready just in case.
-- Peter O'Donnell for IWO