Long Range Weather Forecast For Ireland (16 January 2021)

TRENDS for the week of 16 to 22 Jan 2021

-- Temperatures will average 1 to 3 deg below normal. It will be near or slightly above normal to mid-day Tuesday, then considerably colder for most of the second half of this interval, reaching 4-5 deg below normal at times then.
-- Rainfall will average near normal values, however, almost all of it (now that last night's event is done) will occur on Monday night and Tuesday morning. Wintry showers will follow but these will not give much moisture.
-- Sunshine will average 25 to 50 per cent above normal as all days except Tuesday are likely to bring some sunny intervals. January so far has averaged about 50 per cent above normal over a grid of reporting locations.


will be cloudy with sunny breaks, these more frequent in the east and south. Occasional showers will be fairly frequent in the northwest and less frequent elsewhere, amounts generally around 1 mm but locally 3-5 mm in the northwest. Moderate westerly winds 40-60 km/hr (higher gusts near Atlantic coasts) and highs 6 to 9 C.

TONIGHT will be partly cloudy to clear and some frost will develop, lows -3 to +2 C.

SUNDAY will be sunny with increasing cloudiness, highs near 7 C.

MONDAY will see some brighter intervals at first in the east and southeast, rather cloudy in other regions. One weak front will be edging into Ulster from the Atlantic during the day, while a stronger warm front moves into the southwest by late in the day, bringing rain and moderate southeast winds there. Morning lows -2 to +3 C and afternoon to evening highs 9 to 11 C.

TUESDAY will see intervals of moderate to heavy rainfall, moderate south to southwest winds, and temperatures steady near 10 C. Much colder air will arrive in the northwest by late afternoon and will push into all other regions between then and midnight. Winds rather moderate with this system, as it has a lot of small trough features and the strongest winds will blast around the western periphery offshore, Belmullet may catch those at times on Tuesday night. Temperatures will fall to around 2 C in many areas by late evening and to -3 C by Wednesday morning, as sleety showers turn to snow especially over hills.

WEDNESDAY will be windy and cold; the offshore strong west to northwest winds will move onto land in the morning and spread through all regions by mid-day, reaching 70 to 110 km/hr. Bands of wintry showers will form over the Atlantic and move inland, turning increasingly to snow as they get further inland and especially so when crossing higher ground. Some hail showers may also be in the mix, but the east and south will have some sunny intervals. Morning lows near -2 C and afternoon highs 2 to 4 C but feeling more like -5 to -8 C in strong winds.

THURSDAY will be similar except that the wind speeds will be down into a more moderate range of 50 to 80 km/hr, temperatures in a similar range (-2 to 3 C) and scattered bands of wintry showers with some snow accumulations possible on hills.

FRIDAY will be less windy but will remain cold, with sunny intervals and isolated wintry showers. Lows near -5 C and highs 1 to 4 C.

SATURDAY remains a day of some mystery as model guidance ranges from a brief return to milder conditions with rain, to mixed bands of rain, sleet and snow from south to north, and also some scenarios of a wider snowfall event with strong east winds. Stay tuned on this one, it could go either way.  Temperatures will be determined by which outcome prevails, the all-rain scenario would see a quick rebound to the 8 to 10 C range, the mixed bands would run from that value in the south, to 1-2 C north, and the mostly snow and south coast sleet scenario would probably involve temperatures near or slightly above zero.

By SUNDAY that disturbance, on whatever track it chooses to take, should be over Britain or northern France and colder weather would set in again briefly, with temperatures near 2 C and north to northeast winds. There could be some localized wintry showers with that.

The OUTLOOK for the following week is somewhat uncertain but would most likely see a succession of lows crossing Ireland with mixed bands of precipitation ranging from rain in the south to snow in Ulster and north Leinster. This could shift a bit in either direction, but a lot of the guidance ends mid-week so there is only one model to consult for the second half of the week; that one was trending milder at that point. But the others looked like they might not necessarily follow that lead.

-- Peter O'Donnell for IWO