"Due to easterly gales, with orographic lift, there could be exceptionally high amounts of snow for eastern parts of Wicklow and indeed southern parts of Dublin.
"South Dublin is normally in a rain shadow but in this case with a north-easterly wind, it's the opposite effect.
"In fact we could get up to a metre of snow and this will have a huge knock-on effect over the next few days.
"We in Met Eireann are seriously worried about flooding, over eastern parts, in particular the greater Dublin area."
Dublin Bus, Irish Rail and Luas have all cancelled all services for tomorrow.
Ryanair and Aer Lingus have axed almost all Irish flights scheduled for Friday.
Taoiseach Leo Varadkar has warned "the risk to life and limb should not be underestimated".
All of Munster and Leinster will remain on red alert up to 12 noon tomorrow - but a red weather warning for Connacht, Cavan, Monaghan and Donegal will be lifted at the earlier time of 6am on Friday.
Weather chiefs updated the warnings just before 2pm today after putting the entire country on red alert late last night.
The snow-ice warning for Leinster and Munster takes in 18 counties - Carlow, Dublin, Kildare, Kilkenny, Laois, Longford, Louth, Meath, Offaly, Westmeath, Wexford, Wicklow, Clare, Cork, Kerry, Limerick, Tipperary and Waterford.
And Met Eireann say southern and eastern coastal counties will be worst affected.
The Government say Storm Emma is going to be "as bad as anticipated" as people are urged to stay at home until 3pm tomorrow.
Meanwhile, Galway, Mayo, Sligo, Roscommon, Leitrim, Cavan, Monaghan and Donegal are also on red alert from this afternoon.
Comment: If the extreme cold witnessed this winter in the northern hemisphere is anything to go by, and he isn't be the first weather forecaster to use space weather in his calculations, then it wouldn't be surprising if his predictions came to pass. It's clear we are seeing serious cooling on our planet: