Met Éireann has issued a status yellow snow and ice warning for much of the east of the country.
The warning is in place from 6pm on Monday to 6pm on Tuesday.
Accumulations of between 2 and 5cm of snow are expected during the period in question in the counties covered by the warning: Dublin, Kildare, Louth, Wicklow, Meath and Monaghan.
Modelling by the European Centre for Medium-Range Weather Forecasts shows the heaviest snows will fall in Louth, Meath and Westmeath, but snow will extend from the east to the southwest and west of the country on Tuesday evening.
Large parts of the country are set to get snow on Tuesday, as cold, easterly winds bring wintery showers, falling as snow or sleet, in off the Irish Sea.
Snow is forecast to fall overnight in Ulster and north Leinster.
There will be two separate bands of snow on Tuesday: one across the middle of the country stretching as far as Galway and a second along the south coast in Munster.
What snow will fall on Tuesday may stay on the ground in places because temperatures will only be between 1 and 3 degrees Celsius during the week.
Dublin accumulation
"You could see Dublin get up to 3cm on Tuesday. You could be seeing snow on the ground," said Met Éireann forecaster Linda Hughes.
Wednesday will see a similar pattern, but on Wednesday night a weather front from the Atlantic will hit the cold air from the east, potentially lessening its impact in some areas.
“We are looking for proper accumulations on Thursday. We are looking at 5cm on Thursday widely. We should see lying snow on Thursday,” Ms Hughes said.
Ms Hughes said there was uncertainty about what happens after that, with warmer air likely to follow on behind the weather patterns forecast for the coming days, though parts of Leinster and Ulster could see the snow linger.
In meteorological commentary on Met Éireann's website, forecaster Matthew Martin said the current difference between the sea temperature, which is 8 degrees, and the upper air temperature, which is -10 degrees, is 18 degrees. The differential needed for moisture off the Irish Sea to fall as snow is 13 degrees.
He said the situation should be “sufficient to create some snow showers over the coming days”.
He added: "Current projections indicate a spell of sleet and snow spreading northeastwards over Ireland on Thursday and into Friday, bringing accumulations of snow to many areas. However, the snow may transition to rain in some southern and western parts as milder air attempts to move in from the Atlantic."
Department meeting
A severe-weather co-ordination meeting was held by the Department of Housing on Monday morning to review the weather forecast for the coming days, including the potential impact of snow.
The department’s National Directorate for Fire and Emergency Management crisis management team is meeting daily and working with Met Éireann, the OPW and local authorities to monitor the forecasts and their predicted impacts.
In Britain Storm Darcy has brought snow to large parts of England and Wales. It has been dubbed the "Beast from the East II", a reference to a snowstorm that hit Britain and Ireland that began in February 2018. The latest storm is also hampering the rollout of the Covid-19 vaccine in parts of England.
