Long Range Weather Forecast For Ireland (23 December 2020)

TRENDS for the week of 23 to 29 Dec 2020

-- Temperatures will average about 3 deg below normal values.
-- Rainfall (or liquid equivalent of wintry showers) will amount to 50 per cent of normal values.
-- Sunshine will be near or slightly above normal.


TODAY ... the cold and at times sleety rain will continue with further outbreaks of wet snow likely on higher terrain, with a trend for the rain-snow line to come down slightly in elevation by mid-day as somewhat colder air works into the northeast flow. Temperatures will be steady around 3 to 6 C, falling at times to 1-2 C where snow is falling. Far northern regions will remain dry and some sunshine will get through the clouds at times there. Winds will increase somewhat to northeast 50 to 70 km/hr. There could be some streamers forming over the Irish Sea with mixed wintry showers, at first these may blend into the larger precipitation event, but when that pulls away the streamers may continue or even grow a bit more organized. Other bands of mixed wintry showers may develop from the Atlantic Ocean into north and west Connacht.

TONIGHT ... many areas will clear out and turn quite cold, but a few wintry showers may persist especially in the southeast and over higher ground this may lead to 1-3 cm snow accumulations. Lows -2 to +2 C. Moderate northeast winds will prevent temperatures from falling much further despite any clearing.

THURSDAY (24th) ... Partly cloudy to sunny depending on how much cloud spreads into some eastern and northwestern counties from weak streamer activity or just dry cloud forming in the marine modified layers of the cold air, which will produce highs of only 3 to 6 C. Any localized wintry showers are likely to be brief and light in their precipitation amounts.

FRIDAY (Christmas Day) ... A sharp frost will develop over eastern and some inland southern counties, lows could reach -4 or -5 C in some areas. Cloud and a bit of a westerly breeze will inhibit frost formation elsewhere, lows may be closer to zero C. The daytime will have increasing amounts of high then mid-level cloud, the sun may be dimly visible through those layers by mid-day with a solar halo possible. Some frost will be persistent and only dissipate around late morning. Considerably milder in the north and west by late afternoon and evening in a moderate southwest wind of 50 to 70 km/hr. Highs near 4 C east to 9 C west.

SATURDAY (26th) ... Becoming very windy with occasional rain, temperatures steady 8-10 C for the first part of the day then slowly falling to around 4 C by late afternoon. Winds westerly 60 to 100 km/hr.

SUNDAY (27th) ... Windy and cold with passing wintry showers, risk of some accumulations of snow on hills. Lows near -2 C and highs near 5 C. An interval of sleet or wet snow is likely when low pressure moves through later in the overnight hours (27th-28th).

MONDAY (28th) ... Windy and cold with snow, sleet or mixed wintry showers, some accumulations are possible but near sea level it's likely to keep changing back and forth from rain to snow and sleet. Amounts not too great, around 5 mm liquid which can amount to 5 cms of snow on hills. Temperatures steady in the range of 1 to 4 C.

OUTLOOK ... The details keep changing slightly but each model run we see now has plenty of cold air and very little mild influence, although it's not a 2010 scenario quite yet, the air masses are somewhat less intense and will be over the North Atlantic longer (in 2010 winds were so strong at times that the very cold air rushed from Greenland to Ireland within a day or so, in this case, it's more like a source in the higher latitudes of the open ocean and a three day journey, so that leads to greater modification). At any point there could be a more severe wintry interval coming along in this pattern, as long as it persists and doesn't revert to the westerly zonal sort of regime we were in most of this past month. So in general, would expect a lot of marginal wintry showers through the second week of the forecast period and perhaps well into January, with a risk of colder weather and accumulating snow. Conditions are likely to be quite harsh on higher terrain especially in open country.