Long Range Weather Forecast For Ireland (17 January 2021)


TRENDS continue similar, temperatures expected to be mild to late Tuesday then turning a lot colder; near average amounts of precipitation overall but most of that on Tuesday and Wednesday; sunshine making enough appearances to keep up the pace of this quite sunny January (will report on whether we see any record values of sunshine by end of month).


TODAY will be partly cloudy this morning with the sun gradually disappearing behind high and then medium level clouds streaming in ahead of a complex Atlantic low, but any showery outbreaks of rain later today likely to be confined to Atlantic coastal counties and rather light there. Winds light and variable at first, becoming southeast to south 30 to 50 km/hr at least near west coast by afternoon. Highs 6 to 9 C.

TONIGHT will bring partly cloudy skies, isolated showers, lows 2 to 5 C but some local frost possible in northeast.

MONDAY will be mainly cloudy with a slowly increasing southeast to south wind of 40 to 60 km/hr to 50-80 km/hr later, rain spreading into parts of the southwest and northwest as two frontal boundaries form and begin to work their way east across Ireland by the overnight hours. Highs will reach about 9 C in the south and 6 C in the north.

MONDAY NIGHT will be overcast with outbreaks of rain becoming a bit heavier by morning, 5 to 10 mm in this stage, winds moderate southeast to south 40 to 60 km/hr, lows 3 to 5 C north, 5 to 8 C south.

TUESDAY will bring intervals of rain, gradually adding up to 15-30 mm falls, with some showery bursts and some foggy intervals also, as temperatures slowly creep up to about 11 C in the south and east, staying closer to 6 C in the north where winds will back around to the northeast, while staying south to southwest 30 to 50 km/hr across the south. By Tuesday night, intervals of heavier rain in the southeast, rain turning to sleet and snow over Ulster and this mixture slowly pushing south into the north midlands, as temperatures there fall to near 1 C.

WEDNESDAY the south may remain mild for part of the day but the colder air with the sleety mix turning to wet snow will push gradually south into all of the midlands and even parts of west Munster. Some clearing may follow in Ulster where it will be cold all day. Temperatures will range from 8-10 C in Wexford, Wicklow and the inland southeast, east Cork, to near 5 C in a narrow frontal zone from about Limerick to Dublin, then 1 to 3 C further north. Winds are expected to be rather moderate from the north to northeast in the colder air mass.

A deep low pressure system will form rapidly Wednesday night over the northern parts of Britain and this will end the mild spell for southeastern counties of Ireland, allowing the colder air to start moving faster around the developing storm. Over in Britain, some very heavy snowfalls may develop over higher parts of northern England and southern Scotland. Over eastern Ireland, some bands of mixed wintry showers or sleet with snow on hills appears likely as north to northwest winds increase to about 50-80 km/hr (they will be much stronger over the Irish Sea and north-central Britain).

Peter O'Donnell for IWO

THURSDAY then will see bands of wintry mixed showers, snow on hills and rain/hail likely at sea level, sleet in transitional zones. These bands may be quite strong in places giving thundery showers of mixed varieties. It will be quite cold, around 3 or 4 C, but morning frosts will not be severe as lows will be -1 to +1 C. Winds northwest 50 to 80 km/hr and possibly higher in gusts in exposed locations. Wind chills of about -5 C will be perceived.

FRIDAY will continue rather breezy and cold with scattered wintry showers and a bit of snow at times on hills, some bright sunny spells too, lows near -3 C and highs near +3 C.

The weekend of 23rd-24th looks rather unsettled and the storm track could be right across central or southern counties of Ireland, dividing a rather mild south coast from colder central and northern counties, and producing bands of rain, sleet, and snow from south to north. Temperatures are likely to be in the 7 to 10 C range in the south, 3 to 6 C central and 1 to 3 C north. This split scenario may continue with more lows racing along in a rather active jet stream and crossing Ireland at various latitudes, so the frontal boundaries may oscillate north and south from day to day; the net result will be a rather unsettled week and there is probably some potential for another strong low to form around mid-week, details on that are out of realistic modelling range at this point.