TRENDS for the week of 7 to 13 Jan 2021
-- Temperatures will average 2 to 4 deg below normal, with a gradual increase starting around Sunday.
-- Rainfall or mixed wintry precipitation will amount to 25 per cent of normal values.
-- Sunshine will be near normal values.
TODAY a cold northerly flow will arrive with bands of mixed wintry showers moving into western counties from the Atlantic, and possibly down the east coast also, in north to northwest winds 30 to 50 km/hr. Very cold with highs only about 2 to 4 C. Some snow-covered areas may hold near freezing until the snow is gone.
TONIGHT will see some clear intervals, isolated wintry showers, and very cold again with lows near -4 C.
FRIDAY will have variable amounts of cloud and a cold northerly wind, with scattered wintry showers, some accumulations of snow are possible near east coast and on hills. Highs 2 to 5 C.
SATURDAY will be partly cloudy with some locally persistent freezing fog, morning lows -6 to -2 C, afternoon highs slowly inching past freezing in most areas to the 2 to 5 C range, could reach 7 to 9 C in some outer (west, north) coastal areas.
SUNDAY will be similar although the milder air will sluggishly make inroads and bring temperatures up a few more degrees in many areas, lows -2 to +3 C and highs 5 to 9 C.
MONDAY to WEDNESDAY the milder air will continue to push rather weakly against the entrenched colder air which will only move slowly away from Ireland and then Britain, possibly returning briefly in some areas mid-week. Highs will edge up to more normal values 8 to 11 C. There won't be much if any rainfall in this regime, possibly a few light outbreaks amounting to 5-10 mm total.
The longer term outlook then calls for a return to colder weather on east to northeast winds some time around end of next week or the weekend of 16th-17th. Guidance probably becomes quite unreliable as to strength and duration of that cold spell since part of the justification for it involves near-term but future stratospheric changes.
-- Peter O'Donnell for IWO