Long Range Weather Forecast For Ireland (28 April 2021)

Tonight will become partly cloudy with lows in the 2 to 5 C range, but one or two places could slip a bit lower and have a touch of ground frost by early morning.

Thursday will become more unsettled again with fairly widespread showers and the chance of a few heavier thunderstorms, all moving quite slowly and somewhat randomly although there will be a tendency for northeast to southwest drift of any showers. Rainfall amounts could be 5-10 mm in some places, or even more locally. This will begin to ease the dry conditions that have prevailed in many areas all month but relief from that (if in fact you are seeking relief) will be gradual. Highs on Thursday will reach 12 to 14 C.

Friday will be a somewhat better day with a bright start but eventually a significant cloud cover by mid-day with isolated showers. The wind gradient is never very strong this week but by Friday it almost disappears, so that winds across the country will be quite light and variable in direction. Lows near 2 C and highs near 13 C.

Saturday is likely to be partly cloudy with isolated showers and still on the cool side, lows near 2 C and highs 12 to 15 C.

By Sunday there will be increasing cloud and the threat of some light rain by evening and the overnight hours into Monday, with temperatures in the range of 7 to 13 C.

Monday could see some more prolonged rainfalls in the 10-20 mm range as a weak but persistent low tracks across the country from the northwest. Although the track of this low has lifted further north on guidance today, compared to yesterday's estimates, there won't be much difference to the impact other than perhaps to spread the rain a bit more widely across all regions.

Next week does not look any warmer as the Atlantic, while starting to show some vigour, is largely confined to moving its frontal systems across the Bay of Biscay into France and then Germany, with the cooler air well entrenched over Ireland and Britain. This will keep temperatures a bit below normal values all week (2-8 May) and will also likely lead to occasional rainfalls.

There are some very cold looking patterns generated by computer models later in the week with a good draw on higher latitudes bringing down chilly maritime arctic air masses that could be several degrees below normal temperatures for May, more like 9-10 C than the usual 15-16 C. I would still expect there to be a warming trend at some point in May. This April has been rather rare, it looks as though it will quite possibly turn out colder than March. I don't have a long historical data base available to check that out for Ireland, but over in Britain, where there is such a data base going back almost four centuries, only sixteen Aprils failed to add to the mean temperature of March, out of 362 in the series, so it's about four per cent of Aprils that show this odd result. There has never been a series of March, April, May where all three were colder than the preceding, but May can be cooler than April again in rare numbers of cases. This year with such a cool April I think even a continuation of the pattern would have to add at least 2 degrees to the outcome. In reality it may be more like 3-4. But even that could leave May a bit below its average values. 

 Peter for IWO.