Cold air has deepened its presence somewhat overnight especially in the
northern counties, and it now stands ready to battle the Atlantic which
will be returning to its familiar haunts with a number of forays planned
over the next three or four days, writes IWO's Peter O'Donnell.
Today, expect mostly cloudy skies but the odd sunny break possible
especially away from the streamers which will be generally most frequent
in these areas -- the southeast and near the south coast, central and
northern Leinster occasionally into the midlands, and east Ulster as
well as a persistent band near the north coast of Derry moving across
Inishowen in north Donegal. All of these streamers can be described as
mainly light but occasionally moderate in their intensity, and capable
of dropping 2-5 cm snowfalls in their life cycles. Otherwise the day
will be largely dry in quite a few places that don't see any streamer
activity. Highs today will likely reach about 2 C again in most places,
but could be held down a degree or two on higher terrain. Winds will
start out easterly, but with a slow veering towards southeast late in
the day, in the 40 to 70 km/hr range mainly. This will add about 3-5 deg
of wind chill to actual temperatures.
Tonight, winds will be southeast 40-70 km/hr except in west Munster
where they may increase to 60-90 km/hr. Cold air will be holding strong
in most areas overnight and there could be some local clearing although
some streamer activity and resultant snowfall will also continue, with
the south coast becoming somewhat more prolific as a source due to the
wind shift. Parts of Leinster and Ulster could see localized 2-5 cm
snowfalls also. Lows will probably drop a bit from previous nights due
to some clear patches developing, -4 to -2 C seems probable.
THURSDAY will start out cloudy and raw with southeast winds of 50-80
km/hr. Some locally heavy snow streamers could develop ahead of the main
storm event but many areas will have a dry morning. Snow turning to
sleet near coasts will move into west Munster; the snow will likely be
heavy on higher ground in Kerry and Cork, but wet and sporadic on lower
terrain. In that region, the sleet may turn to rain by afternoon and
temperatures could rise rather steadily to around 7 C. Otherwise the
cold air will be much more resistant (at first) and snow could break out
around mid-day in many counties between the south coast and through the
midlands into Connacht and south Ulster. Amounts by evening could be
5-10 cm and this could cause considerable travel disruption especially
for inter-city road travel. This snow is only likely to change to sleet
right along the south coast and a few kms inland at low elevations. Any
hills in this zone could see 10-20 cm snow amounts. By late afternoon or
evening heavy snow is possible in the southeast and up the east coast
towards south Dublin. Amounts of 5-15 cm are possible, 10-25 cm on the
higher ground in the southeast. Much of the guidance suggests that
Dublin (city) will be in somewhat of a snow shadow situation due to
downsloping from the nearby hills, and snow amounts there could increase
more slowly than in other areas (this remains to be seen). Temperatures
during the snow event will likely be in the range of -2 to +1 C. Winds
will be southeast 40-70 km/hr although sometimes in periods of heavier
snow, east 20-40 km/hr. Any onshore flows such as would be expected in
central Wicklow and parts of Wexford or Carlow would have a potential to
see enhanced amounts.
By THURSDAY NIGHT this snowfall will probably be weakening in general
and also its western flanks will be changing over to sleet then rain as
somewhat milder air creeps slowly further east, reaching perhaps a Sligo
to Waterford line by about midnight or so. The rain in most cases will
be rather light at first, becoming heavier later in the night in west
Munster. Winds will continue southeast 40-60 km/hr where it is snowing
or sleeting (and this activity will also be weaker in many cases), and
will become south 50-80 km/hr in the milder sector with the rain.
Temperatures will remain about zero to +1 C in the snow/sleet areas of
east and northeast, and will rise to 4-5 C with the milder air oozing in
(over snow that is melting, so some fog is likely with that).
By FRIDAY some areas of sleet and snow may still be present especially
in North Leinster and Ulster, and the further push of mild air will come
to a halt for a time, with temperatures 0-2 C in the northeast, and 5-8
C elsewhere. Rain may become heavy at times in the south especially
near hills. Winds southerly 50-80 km/hr. Friday night could see a brief
push back to the west of the colder air which will be taking advantage
of a weaker portion of the incoming Atlantic frontal system at that
time. This may turn the rain back to sleet or wet snow in some areas of
Connacht and the midlands.
Then on SATURDAY the milder air will slowly start to gain further
control but in doing so renewed snowfall or sleet could develop over
parts of north Leinster and rain will spread further north and east once
more. Eventually most of the guidance now agrees that milder air will
push all the cold air out of Ireland and some parts of western Britain
before running into greater resistance around central to eastern
England. So for Ireland on Saturday, would expect most areas to be
overcast with periods of rain and strong southerly winds 60-100 km/hr,
with 20-40 mm rainfalls near the south coast, considerably less most
other places, and temperatures 7-9 C.
SUNDAY and MONDAY will likely continue with the rain, wind and milder
temperatures, and rainfalls could become heavy to excessive near the
south coast. Where this rain falls over hills that develop a heavy snow
cover, strong melt-driven runoff could lead to stream flooding in the
southeast, south central and parts of the southwest as well as possibly
Connemara. Temperatures will be near 8 C much of the time.
Now it should be said there is still a slight chance that most of this
guidance is wrong about the mild victory over the cold and that the cold
might put up a longer or more effective fight, so that needs to be
watched, but the chances seem fairly good that mild is going to win
based on the current model consensus. There will be times later in the
week when renewed Atlantic systems come in but with some cooling of the
general south to southwest flow between systems, they may not be
starting off as mild as the previous system ended, so temperatures could
fall back to the range of 2-5 C then go back up at intervals to around
8-10 C. Just looking at the guidance in broad general terms I would say
there is likely a chance of one more cold spell taking place late in the
month or more likely into early March. So I don't think this will be
winter's "last hurrah" before a spring pattern dominates.