Your daily forecasts from Boards.ie weather forum (NO CHAT)

No worries, the errors are probably a mixture of over-estimation in some cases, and model error today (had the models been right for today when those forecasts were issued, I'm sure it would have been snowing across the southeast, the low that was shown going into south Wales ended up in northwest France. People in northern France are getting buried in snow today, just check "meteociel.fr" and look at the observations that come up on the map. Everyone north of Paris is talking about 20-25 cms of snow.

I appreciate the positive comments too. But I'm not too worried about taking some flak as long as it doesn't happen very often, the goal is of course to have it happen never, but as someone comments in another thread (I think), I don't claim 100% accuracy or superhuman powers (outside of my social life, of course). I would mention the long-range forecast as being reasonably accurate so far, in fact with any luck it may continue to do really well, and that's what I'm really working at, the short-range application is mostly to keep focus on the research (in other words, to give me a reason to keep watching very carefully, otherwise in this sort of research you tend to focus mostly on very large-scale features and miss a lot of detail.)

By the way, forecast update ... 06z GFS sides with my concern about no substantial warming trend, in fact, it looks quite cold all the way through to the end of its run on 4 Jan now with a ridge holding the mild air back at Christmas, and one time after that, before building up strongly again as the Atlantic goes totally back to sleep after this little stumbling around episode at Christmas. Unreal looking patterns this winter that only our ancestors saw (except they didn't, not being on the internet).

Almost an Update _ Sunday, 2230h
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Even the most reliable guidance (like HIRLAM) is changing every three to six hours on small details. At the moment, I am left thinking that sea effect streamers are gaining in potential for east coast counties, while travelling lows to the south are weakening in potential for snow in the inland southeast -- but then if the streamers get particularly strong they can reach the inland southeast. This applies in particular to tomorrow for streamers and Tuesday for hit or miss coastal snow in the south.

So I don't consider this an update, just a reminder of a continuing series of slight or even moderate chances for snow, which would seem to include some fairly robust streamers now making landfall around Dublin. These are likely to keep going for several hours before dying out, then perhaps reloading on Monday.

It will certainly continue bitterly cold in most areas tonight with Ballyhaise already at -12 C and even colder in parts of Ulster.

The odds on the Christmas to 27th period having a warmup are about 50-50 but that's for any warmup including a partial one that only reaches the south. The most likely outcome in my view would be for bitter cold to try to hold on in the north all day 25th, with sleet or snow possible across parts of the south, then for these bands to move north on the 26th with rain likely in the southwest, followed by a gradual weakening of the fronts and a slow return to colder weather over a day or two. There is some potential here for a snowfall of quite large amounts if the front were both strong and slow-moving. This will become our prime focus, I think, as we approach Christmas Day.

UPDATE _ Monday, 8 p.m.
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Adding these details to the existing forecast.

Locally heavy snow is likely to continue in some parts of Meath, Dublin and Wicklow with 10-20 cms more overnight in some places. Our discussion threads have the best details on when and where, also watch for renewed thundersnow around midnight especially.

This east coast activity may spread further inland at times and could begin to merge with weak outbreaks of light snow near the south coast later tonight. This merged activity could give highly variable amounts to the southeast, with local 5-10 cms possible but this will probably turn into a radar watch type event.

Also, some 2-5 cm snowfalls appear likely in Donegal and north Mayo overnight from hit or miss snow showers in weaker sea-effect streamers moving towards the southwest.

As the existing forecast says, tomorrow looks a bit more conducive to snow across the south at least on a sporadic basis, but east coast streamer activity could continue and there is some chance of this turning into a heavy sustained snowfall event lasting into Wednesday. Later updates may address this possibility. The model guidance is inconclusive on that, not ruling it out or making it too obvious either. (mothers don't let yer sons grow up to be forecasters ... )

All of the above suggests that bitterly cold night temperatures may get squeezed into smaller zones inland but these will likely continue the next few nights and the bitter cold could intensify before the spell terminates or fades out. On that question, no change in my thinking, I am seeing a lot of weaknesses in the rapid warming scenario for 25-26 Dec and would stress caution as this seems like less than a sure bet to me ... any outcome between a partial thaw and mixed precip, to sustained cold and possible snow, remain on the table. Some models led by the UKMO show this but also, the general climatology of this situation and past unhappy experiences of the forecasting world with stubborn cold hanging on would suggest caution. Of course, it could just go to a quick thaw, that remains a possible outcome. There are such mixed signals that it seems prudent to say that this rapid thaw is more or less of a toss-up.

A reminder that the Moon sets in total eclipse at around 0745 to 0815 Tuesday, for the few who might have clear skies at that time.

UPDATE _ Tuesday, 6 p.m.
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The large-scale forecast remains valid ... here are some updated details.

The heavy snowfall ALERT remains in place for Dublin, Wicklow and parts of MEATH and is extended to significant snow in Kildare, Carlow, Wexford and possibly parts of Louth, Laois, Tipps, Kilkenny, Waterford. Further snowfall amounts now into Wednesday (and possibly Thursday in some cases) could easily double existing snowfalls, and bring additional 20-40 cms of snow to some parts of this region. For the counties being added to the alert, new amounts of 5-15 cms likely and 10-20 cms possible. Coverage may not be complete with gaps in the snowfall as it moves further inland. Some flurries may develop further inland and in parts of Ulster where 2-5 cms could fall in some eastern counties eventually.

Meanwhile, the southwest (mainly inland Kerry and west Cork) may continue to see a few more centimetres of snow but this area is slowly degrading and seems likely to pull out to sea (southeastward) fairly soon -- city of Cork may escape this snowfall -- but eventually there could be further activity from the eastern source spreading that way in the next 36 hours, amounts likely to be small.

Most other parts of the existing forecast still valid, my thoughts on Christmas Day and the two or three days afterwards have not really changed and I honestly don't think the models have that much of a handle on the situation yet, so I am reluctant to keep changing with them until I see better indications of a real trend. It makes sense to me that temperatures would rise at least slightly for 2-4 days some time between Christmas and New Years Eve then fall back in the new year with renewed blocking and the additional influence of very cold air masses moving west through northern Europe. The chances of a very significant thaw and even flooding have to be considered but I'm not ready to declare this "on" at this time.

Watch for further updates as required.

Wednesday, 22 December, 2010
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TODAY ... While snow has largely ended over the southeast as of 0630h, there remains potential for it to resume at times by late morning and afternoon, in a few streamers coming inland from Meath south to Wexford. Some further snowfalls then may be anticipated but amounts may be much less than yesterday. Watch for updates with estimates of new snowfall amounts. Otherwise, most of the country will have clear to partly cloudy skies over top of any layers of low-level cloud and ice fog, and the sun should break through in most places from time to time. Very cold for most with highs only -5 to -1 C (possibly a bit higher near east coast if streamers develeop). Winds will increase somewhat to NE 15-25 mph in exposed areas although central valleys will remain mostly calm. A few flurries giving 2-3 cms could hit parts of Donegal and north Mayo also.

TONIGHT ... Generally clear and very cold with widespread ice fog, but northwest counties will be cloudy with a few periods of light snow, and some streamers may still be active near Dublin and Wicklow. Lows will once again be well down into the -10 to -15 C range except where winds are onshore, and there closer to -5 C.

THURSDAY ... A weak trough may bring scattered flurries near north and east facing coasts, and otherwise partly cloudy with some sunny intervals, quite cold again with highs generally -4 to +1 C.

FRIDAY ... Early morning severe cold, possibly reaching -18 C over snow fields and -12 C even out towards the coast in some areas. Widespread ice fog likely, that may not clear all day in some places. Weak sunshine for other regions. A stray flurry possible, but largely dry. Highs -7 to -2 C.

SATURDAY, CHRISTMAS DAY ... For Ulster, Connacht, Leinster and east Munster, expect a dry start with some sunshine in the morning, extremely cold inland, some ice fog; by afternoon, cloudy, some light snow possible as winds pick up to SE 15-25 mph. Morning lows about -12 C to -7 C and afternoon highs -3 C to +2 C ... for West Munster, cloudy with outbreaks of light snow or sleet, possibly becoming rather heavy at times, morning lows about -8 C around midnight, highs reaching -2 to +4 C. Winds increasing to SE 20-35 mph.

SUNDAY, ST STEPHEN'S DAY ... Cloudy, some fog or ice fog, snow in parts of Ulster, Leinster, inland Connacht, freezing rain a risk for later in central counties, possibly turning to a cold rain in south and southwest. Temperatures slowly rising all day and could reach +1 C in Ulster, +3 C central and +7 C southwest. Winds SSE 20-40 mph. There remains some risk that this forecast, based on current model consensus, might change to more of a cold/snow scenario in general. Watch for updates.

MONDAY 27th ... Possibly milder with some thaw conditions in west and south. Heavier snow fields in Connacht and Leinster not likely to thaw or melt very quickly but this could lead to fog and widespread slushy conditions. Once again, this is perhaps 70% likely, the other 30% chance would involve less warmth and something like sleet or wet snow hanging on. But for now, we'll go with a general temperature range of about 3-7 C east and north to 6-9 C south and west.

OUTLOOK ... A few more relatively mild days should lead to clearer roads and pavements, with any luck, and slow melting of lying snow. There would be some light rainfalls, possibly sleet or wet snow over north on higher terrain, and highs generally in the 5-8 C range. This is likely to end some time around the New Year with another cold outbreak from either the northeast or the north to northwest. Details should be clearer by about the 27th on that next cold spell.

MTC's local weather ... Cloudy here on Tuesday 21st, some light rain by this evening, and a bit milder with high of 8 C.

WX HIGHLIGHTS ... A severe storm hit eastern Canada, this being the one being tracked across the Atlantic for possible warming trends over the holidays. The effects in Nova Scotia, PEI and New Brunswick were mostly rain and strong east winds with storm surges in places due to the full moon high tides and wind action. California has had torrential rains and mountain snows, and so has New South Wales in Australia. The snow there is at high elevations in the mountains east of Canberra. It's probably above 20 deg C in the big cities but this is rather cool for Australia in what amounts to June down under.