Status Yellow Snow/Ice warnings have been issued for 18 counties.
Met Éireann is warning of a risk of snow accumulations to lower levels in 13 counties during the first half of Wednesday. The affected counties are Carlow, Kildare, Kilkenny, Laois, Wexford, Wicklow, Offaly, Donegal, Leitrim, Sligo, Cork, Tipperary and Waterford.
The UK Met Office has issued separate warning for Antrim, Armagh, Fermanagh, Tyrone and Derry where snow and ice may bring some disruption.
Shortly after midnight, rain will push into western counties and extend eastwards, turning to sleet an snow in some areas. The band of rain, sleet and snow will clear southeastwards during Wednesday and will be followed by scattered wintry showers extending from the northwest.
IWO Senior Forecaster Peter O'Donnell says, "The band of precipitation may begin to produce snowfalls of 1-3 cm over parts of south/central Connacht, the midlands, and south Leinster, parts of inland east Munster during Wednesday. There is potential for this to increase to a higher amount and if I see justification for that I will update the forecast this evening. Even with this fairly small amount of snow, mixing with sleet and patchy freezing drizzle, roads may become icy especially untreated or lightly traveled routes."
"It will likely stay dry from around Dublin north into north Leinster and most of Ulster. Any change in the track or intensity of this system could bring snow further north however. Highs will be only around 2 C in many areas, light east winds to the north of the track of the low, and variable mostly westerly breezes in the milder sector, where temperatures (affecting most of Munster at some point if not all day) will reach 5-7 C with light rain," he added.
Ireland's weather is set to remain cold over the coming week but extended periods of dry weather are expected for many parts of the island.
Thursday will bring a return to partly cloudy and windy conditions with temperatures between -3 C for overnight lows and +4 C for daytime highs. Scattered wintry showers are likely, along with fairly generous sunny breaks too.
New Years Day (Friday) will also be partly cloudy and cold with scattered snow showers. The freezing level will be very slowly descending to levels where snow could begin to fall at or near sea level, especially in any vigorous showers where the rate of fall doesn't allow time for the falling snow to melt. Lows near -4 C and highs of about 3 or 4 C.
Peter O'Donnell says the outlook continues to suggest a long cold spell with more and more anticyclonic and easterly influences, both of which would argue for slightly colder temperatures, and in Leinster, also more chance of significant snowfalls.
He added, "I would say we're maybe one turn of the dial away from something memorable with this setup but on the other hand if the dial is turned the wrong way it could all end up seeming rather ordinary too. For winter weather lovers, at least we can say we're in with a chance this winter. And of course, probably 80% of memorable winter weather events tend to happen later than this, December 2010 was an anomaly in that regard. Late January to mid-March seems to be the part of the winter that produces more often than others, historically. It no doubt is related to colder ocean temperatures and the expansion of the arctic ice pack, but those are factors that have become weaker in recent decades, so we're fighting against the trends to get anything really memorable nowadays. (Late Feb 2018 showed that it can be done, however)."
In its updated monthly forecast, the UK Met Office says, "Likely remaining cold throughout this period (3-12 January) with the risk of wintry hazards. It will be dry at times, with the driest and clearest conditions likely in the west and northwest, and showers likely further east. These showers often wintry with hill snow but with a chance of snow falling to lower-levels at times. There is potential for spells of more organised precipitation, accompanied by stronger winds to move north from the continent into southern and central areas. Additionally, there is also the potential for precipitation to move into northern areas if high pressure declines. Both scenarios could bring an associated snow risk particularly over hills. Temperatures are likely to be below average bringing the risk of frost and freezing fog along with very cold overnight temperatures over any snow cover."