TRENDS for the week of 21 to 27 April 2021 --
-- Temperatures will average near normal or within 1 degree where slightly below normal.
-- Rainfall will average near zero to near the end of this period,
picking up slightly in the days just after this weekly interval ends. A
few parts of Ulster could see 25 per cent of normal rainfall by next
Tuesday.
-- Sunshine will average 25 to 50 per cent above normal, except in some cloudier coastal locations.
-- Winds will continue to average only 20 to 40 km/hr at their peak and calm spells at night will be the rule.
FORECASTS
TONIGHT will see some clear intervals, fog or mist in places, and lows
generally around 2 to 5 C. Isolated patchy ground frost may return.
THURSDAY to SATURDAY will be a pleasant sunny interval for most places,
still the threat of some coastal cloud at times, and the same
temperature regime as today although it could warm up by a degree or two
for all regions. So expect highs 13 to 17 C for most areas, and
overnight lows in the range of -1 to +4 C, with patchy frost in a few
locations.
By SUNDAY and MONDAY a weak frontal trough to the north will be exerting
some influence and spreading variable amounts of cloud into the region.
It may lead to some drizzle in north coast Ulster at times, although
Tuesday to Wednesday look a bit more unsettled in the north.
Temperatures will be slowly edging back down towards the range of 11 to
14 C by day but nights will not get any cooler due to the increased
cloudiness. Then it appears likely that another cold spell will develop
towards the end of the month and temperatures could fall a few degrees
further with highs possibly not far from 10 C by the last days of April
into early May. This will all end up in a transitional scenario where
the cold and blocking get pushed back into the far north by a more
vigorous jet stream, some time around the first week of May or possibly a
bit later. Some time around mid-May it could be quite a bit warmer than
it has been this month.
Peter for IWO