FI Charts ( T120+ onwards) Winter 2021/2022 **READ MOD NOTE IN FIRST POST**

Looking at all the GFS 12z runs it's almost a 50/50 split between a mild Christmas week to New Years period vs a cold to very cold period. One options appears to be removed from the table and that is a dry and high pressure dominated period between Christmas and New years.

Uppers generally -8 to -10 and negative dewpoints if we want guaranteed snow and to avoid melting rapidly. Anything milder and it's likely to be marginal particularly near coastal counties. Today's runs can only be better than yesterdays. We need that low to sink properly south. If it slides across Ireland then cold rain for most and proper cold air may not get in.

GFS 00z is very mild for Christmas Day and Stephens Day but turns much colder from the 27th and stays very cold to the end of it's run. It may not get there for Christmas but at least there is some decent cold after.

This GFS ensemble member is a complete outlier and going for nearly 50cm of snow for Meath/Dublin. Extremely unlikely to happen.

GEM is similar but is alot milder with a chance of it turning much colder, it also has some nasty looking low pressures around this time period.

ECM alot better than yesterday but we really need these lows to sink further south, we are on a knife edge between very mild weather along the south coast vs much colder air north of that.

As for snow there is no real point looking at that yet. We're still a week away from the potential cold and so many of the colder runs have mild air very close to out south so we need to get the cold and blocking properly in place before looking at any snow potential.

For Christmas Day itself it does appear we have lost the trend to keep things high and dry as it turns progressively more unsettled from about the 23rd of December. The final week of December is likely to feature plenty of precipitation which may be mostly of rain over Christmas but turning more wintry in nature after Stephens Day. Snow is looking more and more likely at some point between the 27th and New Years Eve, but before we start getting excited we need another 3 to 4 days to see where does the cold go and will we get very cold air along with decent levels of precipitation.

GFS 6z rolling out. Similar to the 0z it's going for a mild and wet Christmas Day particularly along the south coast and it begins to turn colder from the north. Rain or showers will begin to turn wintry from Stephens Day.

By Stephens Day temperatures in the 2 to 4C range and sub zero by night. After this temperatures may struggle to get above 0C across parts of Ulster and Leinster but closer to 3C generally. New Years Day could be an ice day with a long fetch northeasterly sourced from svalbard down across Ireland with a baltic north-east wind chill. By this stage anything that falls out of the sky would be of snow and temperatures in some eastern areas may struggle to get above -2C or even -3C.

If this was to verify night time temperatures close to -10C would be possible or even colder if there was lying snow. This would probably be our coldest spell of weather since December 2010.

Polar lows are also a possibility with this set up where showers would merge forming localized snow storms.

If this GFS run was to verify this would be a fairly substantial and bitterly cold setup that could take a week or more to shift. This could well be a cold outlier as this is a very cold run indeed.

On this particular run snow is covering much of the country by this point and parts of Leinster particularly around Wicklow would be buried in snow.

It's important not to get too excited over this particular run as this is so far away and very unlikely to verify as is but great to see the GFS playing around once again with some proper mid winter cold.

Similar to the week of Stephens Day 2001 to New Years Eve 2001. That was a very snowy few days over the Christmas week.