Long Range Weather Forecast for Ireland (15 December 2020)

This eumetsat Airmass image from 1:00pm shows tonight's system winding up to the southwest of Ireland. It will track north north east, bringing strong winds and heavy rain for most parts with a heightened risk of coastal flooding in southern coastal counties in particular

TRENDS for week of 15 to 21 Dec 2020
-- Temperatures will average 1 to 2 deg above normal values.
-- Rainfall will average 25 to 50 per cent above normal values in the south, to near normal in the north.
-- Sunshine will average around normal also.
TODAY will be partly cloudy with some decent sunny breaks in the east and north, and scattered showers in parts of the south and west, one or two of which could be locally heavy with hail (south Clare, Limerick, west Cork seem most at risk). Highs by late afternoon near 10 C. Winds rather moderate in most areas, southeast 40-60 km/hr for west Munster, increasing by late afternoon to 50-80 km/hr, as rain from the approaching storm arrives. (if it gets a name, it would be Bella, not Brendan).
TONIGHT will become rather stormy across the south and east in particular, with the onshore strong winds raising concerns about coastal flooding as we have just had the new moon. Winds will be southeast 70 to 110 km/hr and there could be isolated higher gusts. Rain will amount to 15 to 25 mm in many areas. Temperatures will be steady near 10 or 11 C.
WEDNESDAY ... the storm will weaken gradually as it moves further north, and a dry slot will rotate around into parts of west Munster and south Connacht, as what's left of the rain becomes more showery and arcs out over the Irish Sea by late morning. The strong winds will gradually abate but not until after an interval of strong westerly winds around Galway Bay, and west Munster. Temperatures will be near 9 C by mid-day and may remain steady near that reading into the overnight hours with further rain likely at times.
THURSDAY will be cloudy and mild with outbreaks of rain, 15 to 25 mm by Friday morning. Winds rather moderate at about 50-70 km/hr from the south to southwest, temperatures steady 10 to 12 C.
FRIDAY will see the rain tapering off to showers, moderate southwest winds, temperatures about 8 to 10 C.
SATURDAY will become partly cloudy with isolated showers, moderate southwest winds, highs near 8 C.
SUNDAY will be mostly cloudy with occasional rain and highs near 8 C.
MONDAY into early TUESDAY, another Atlantic storm may move into the south with locally strong winds and heavy rains, temperatures will be 8 to 11 C in the south but only 4 to 7 C further north where winds may be more easterly as the low centre tracks through central counties. Although there's no strong indications of wintry mixtures, those could happen on higher terrain at least.
By Wednesday (23rd) it will be breezy and turning colder in a moderate to strong northwesterly flow, with scattered wintry showers likely then, highs only 4 to 7 C. Thursday 24th will be similar, then Christmas Day (Friday 25th) is likely to be bright but rather cold with morning frosts and afternoon highs of 4 to 7 C. This colder spell could dominate the end of the month but a brief return to Atlantic frontal systems is possible between Christmas and New Years.
My local weather on Monday was overcast with highs near -2 C. We're expecting a heavy snowfall here in the next day or two as a strong Pacific low moves into the region, 15 to 30 cm being the range likely around these parts. This will bring strong winds and heavy rainfalls to the lower elevations close to the coast. A separate storm system is developing over the south central U.S. heading for the northeastern states which could get a significant snowstorm also by Tuesday night or Wednesday.
-- Peter O'Donnell for IWO