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

Wednesday, 15 December, 2010
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Advance ALERT ... Rapid freeze likely on Thursday morning in north, by afternoon in south; rain showers will turn to sleet, hail and then snow in many places with a sharp drop in temperatures. Roads and pavements will become icy and in some northern counties, also snow-covered, in a matter of an hour or less, leading to dangerous travel conditions. See forecasts for more details on that. Also, 5-15 cms of snow possible in west and north on Thursday and Friday. Further significant snowfalls more widely over the weekend. Details in forecasts.

TODAY ... The calm before the storm, with partly to mostly cloudy skies, slowly strengthening WNW winds at 15-25 mph, and eventually, a few light showers mainly northwest of the Midlands. Rather mild again, with highs in the range of 7-10 C (mildest in coastal Connacht and west Munster).

TONIGHT ... For all but the far north, a mild and cloudy night with periods of rain, not likely to be very heavy (2-4 mms), moderate westerly winds at 20-30 mph, and lows of about 3-5 C. In the far north, these conditions will suddenly change to cold, windy and squally as rain changes to hail and snow. This change will be felt throughout Ulster by about sunrise.

THURSDAY ... The main feature of the day's weather will be a sudden change to much colder, wintry weather. The timing of that change will vary from morning in the mid-north, to late afternoon in the south coastal counties. Before the change, it will continue mild, breezy and showery with temperatures steady 5-8 C. The changeover will involve squally showers, some thunder, turning quickly to hail, sleet and then snow, with roads becoming very icy. Temperatures will fall to -3 C in the north and -1 C in the south. Winds will increase to NW 30-50 mph (gusts to 60 near west, north coasts). Snow may break out over large parts of Connacht and Ulster, spreading at times to West Munster, inland Leinster, with flurries further south and east. The heavier snow could accumulate to 5-10 cms by Thursday night.

THURSDAY NIGHT ... Very cold and windy with temperatures falling to a range of -6 to -3 C inland and east, and near zero C west coast, -2 C south coast. Widespread snow and icy roads, 3-7 cms of snow in all but a few coastal districts where sleety hail or rain showers may mix in. Winds continuing strong, NW 30-50 mph with some higher gusts. Some thunder-snow especially around Mayo, Donegal, Galway, Clare nearby parts of other counties.

FRIDAY ... Windy and very cold, with passing flurries or heavier snow squalls, mixing near west coast at times with hail and sleet. Winds WNW 30-50 mph except NNW 30-50 mph in eastern Ulster. Highs only -2 to +2 C (except possibly 4-5 C in coastal Kerry). Some further snow accumulations mainly north and west to 10 cms, but some snow possible further east and south. Risk of thunder-snow, icy roads widespread, also intervals of blinding sun between showers combining with bright surfaces at this low-sun time of year can be a real hazard.

SATURDAY ... The early morning may be bitterly cold due to some clearing and much lighter winds, but coastal Ulster may see heavy snow, and west coast may see mixed wintry showers. Lows inland, east and south in the range of -4 to -10 C. Around the coasts especially west and north, lows about -2 C. ... During the day, outbreaks of heavy snow, mixing near sea level with sleet, inland accumulations of 5-10 cms likely, winds generally from a westerly direction across the south and from the north or east elsewhere. Highs -3 to +1 C for most.

SUNDAY ... Risk of some moderate or heavy snow with greater accumulations inland from south coast, on higher ground especially, and through the inland southeast, on the east coast and in parts of Ulster (10-15 cms potential in these zones) ... more showery in Connacht, snow amounts 2-5 cms. Very cold with lows near -5 C or lower in some areas, although -2 C south coast, and highs in range -2 to +1 C.

MONDAY ... Further snow likely, 5-15 cms in some areas, may mix with sleet near coasts. Winds becoming rather strong northeast, heavy streamers for Dublin and Wicklow may develop. Very cold with lows near -5 C and highs near -1 C.

TUESDAY ... Snow may end gradually with some wintry sunshine especially in north. Lows -6 C on average, could reach -12 C in parts of Ulster ... highs around -3 C inland to +2 C coasts.

WEDNESDAY ... Wintry sunshine at times, very cold. The morning lows here may be the coldest of this spell (-15 to -10 C potential inland). Highs may not reach freezing in many areas.

OUTLOOK ... Some chance of another wintry storm by Thursday 23rd into Friday 24th (Christmas Eve). A lower chance that this may turn to a milder rain event. Continuing to assess this, models seem challenged at this range. Would count on further cold and snow in the weeks to follow.

Meanwhile, over here, the day on Tuesday was showery and a bit cooler, with sleet mixing in at times, temps 5-6 C. There was a massive lake effect snowstorm west of London, Ontario from Lake Huron that dumped incredible amounts (100-150 cms) in narrow bands. This is slowly dying out now. But those snowfalls are quite limited and many areas have had cold, dry weather in the east today.

Updates will be posted here rather than in discussion threads first. So if you're looking for updates, they will appear here first.

May update around 9 to 10 p.m. but forecasts seem to be generally on track.

Re the UK forecasts, if by that you happen to mean any part of Northern Ireland, my approach is to include the six counties within the forecasts as a general rule. Otherwise, would refer interested parties to such sources as

http://metoffice.gov.uk

http://net-weather.co.uk

and a smaller UK forum where I issue some of the daily forecasts and alerts,
Weatherchat Plus

http://s2.excoboard.com/Weatherchatplus

As I think is widely known in the Irish weather community, while M.T. Cranium is a very apt name for one with this much space between the ears, I have such meat world names as Peter O'Donnell (my birth name) and Roger (J) Smith (my assumed name) and in Canada I am sometimes known as Amazing Negative Stereotype Man, the first citizen to acquire every possible negative stereotype and therefore win an award as First to Walk to the North Pole.

If you happen to go for a look-see at Weatherchat Plus, that's a fairly small membership forum but we do have about four members from Ireland there, and the bulk of the membership is Midlands-based as the forum was started by folks from that part of England (where coincidentally I was born before being tossed on a boat to Canada as a mere infant).

As boards members have been extraordinarily kind to this citizen of no particular country, I tend to identify more and more as a cyber-resident of Ireland even if physically far removed, and indeed when I read accounts of being a "Canadian" I think that notion has been disproved on almost a daily basis over half a century, a fact now pretty much confined to my passport. Quite true the saying that no prophet is without honour except in his own country. :cool:

Forecast update ... Wed 15 Dec 2010 ... 8 p.m.
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In general, the morning forecast remains valid, but I am updating more to emphasize that some of the potential events now appear more likely to verify near top of ranges suggested.

TONIGHT ... Cloudy and relatively mild with scattered outbreaks of light rain mostly after midnight, winds picking up gradually from a westerly direction to reach 20-30 mph, temperatures steady 2-4 C for most. Late tonight, turning very windy and much colder in north coast Ulster, with hail and snow showers spreading rapidly south to cover most of Ulster by sunrise, and some parts of north Connacht and north Leinster by 0800h. Snowfalls in this zone only 3-7 cms. Temperatures falling to -3 C inland, +1 C near coasts, in the north only.

THURSDAY ... Very windy and turning much colder from north to south. The milder air will remain in place for the morning in central counties and to mid-afternoon in the south. In all areas, a rapid change to much colder weather as winds shift from W 25-40 mph to NW 30-50 mph with higher gusts in Connacht. Earlier rain showers will change to hail, sleet and snow in a squally fashion with some thunder and lightning. Earlier snow in the north may intensify to heavy snow at times giving 10-15 cms locally there, while further south amounts will average 1-3 cms and a few spots may escape snow but nowhere is likely to escape icy roads by evening.

THURSDAY NIGHT, FRIDAY ... Continuing windy and very cold with frequent squally showers of hail and snow, considerable accumulations possible but mostly in Ulster and Connacht, west Munster, parts of north, west Leinster where amounts will average 5-10 cms and reach 15 cms locally. Highs for the day only -3 to -1 C in north (inland) and 2-4 C in southwest, 0-2 C in southeast and east. Some intervals of bright sun will also be hazardous because of glare off snow and ice at low sun angles. Roads becoming very treacherous in many counties but with highly variable conditions too, travel with care if you can't avoid travel.

WEEKEND ... Bitterly cold to start with some clearing late Friday night and lows generally -7 to -4 C but as low as -10 C in any northern valley locations under clear spots in the general overcast. Ice fog likely over central counties. Then snow likely to spread in or break out locally, heavier in the northeast at first, then becoming rather heavy in many areas, local accumulations of 5-15 cms both days, potential for near-blizzard or blizzard conditions with Dublin possibly near the higher snowfall zone that is likely to extend from about Meath to Laois and Tipps, but should emphasize that heavy snow could develop quite widely outside that zone too. Maximum snow accumulations could reach 20-30 cms. Some thunder-snow likely. Winds will increase at times to NE 20-40 mph blowing this snow around, in temperatures in the range of -2 to +1 C (could stay colder than that in parts of Ulster and inland Connacht).

MONDAY ... The above snowstorm to blizzard conditions may continue or may ease slowly, but in any case, there will be a lot of snow on the ground and temperatures near -1 C with potentially strong E to NE winds at times.

TUESDAY to THURSDAY ... Some snow could continue in the south, and flurries or freezing drizzle will keep roads icy in many areas, but this could be a somewhat drier period with breaks in the overcast and very cold temperatures at night as a result, lows may fall to -8 C or lower, highs will remain in the range of -2 to +2 C.

OUTLOOK ... I tend to discount any suggested warmings but there is a chance of milder weather around Christmas, however, I think there is an equal chance of a further period of snow with the mild air held back to the southwest.

For those with an interest in weather in the U.K. or northern France for their travel plans, it seems quite possible that the snow in Ireland will break out over large parts of the U.K. as well, and may extend at times into northern France. Parts of central England are likely to see the worst of the snow there, 20-40 cms potential. Eastern Scotland may see some snow, but central Scotland and northern England could see bitterly cold overnight lows during the period, as low as -20 C in some places, but generally -10 C or lower.

Further updates as required ...

Thursday, 16 December, 2010
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ALERT for snow and blowing snow in northern, northwestern and some western counties today, with some local accumulations of 10-15 cms. ALERT for icy roads developing from north to south after a frontal passage (see forecasts for timing). ADVANCE ALERT for further snow, icy roads, bitterly cold temperatures Friday to Monday and possibly beyond.

Brief situational update -- all guidance continues much as yesterday, with some range between models, requiring a blend and some intuition to come up with your forecast, but of more immediate interest, a small "polar low" may be forming upstream south of Iceland heading for Connacht and Donegal later, and this may necessitate a slight upgrade of snow potential -- will be tracking this closely. Meanwhile, the arctic front is about to sweep through Ulster, and I'm expecting it to reach Dublin to Galway by 1230 to 1300h, then about Shannon to Waterford about 1500h, finally Cork about 1630h. Winds will veer to NW before this front arrives, as there is a pre-frontal trough. But temperatures only drop after the main front goes past, and based on reports from northern Scotland, they drop very quickly to below freezing. Thus the urgency of the alert for icy roads and sudden reductions in visibility due to heavy snow.

TODAY ... Very windy and turning much colder from north to south. The milder air will remain in place for the morning in central counties and to mid-afternoon in the south. In all areas, a rapid change to much colder weather as winds shift from W 25-45 mph to NW 35-55 mph with higher gusts possible especially in Connacht. Morning rain showers will change to hail, sleet and snow in a squally fashion with some thunder and lightning. In the north morning sleet or hail may intensify to heavy snow at times giving 10-15 cms locally there, while further south amounts will average 1-3 cms and a few spots may escape snow but nowhere is likely to escape icy roads by evening. A few sunny breaks may develop behind the front in the south and east but passing flurries may suddenly reduce visibility even there. Finally, an interval of heavier snow may develop in the northwest towards evening.

Morning to mid-day highs of 8-10 C will contrast sharply with later temperatures falling below zero to about -3 C. At this stage, wind chills may reach -10 C.

TONIGHT ... Windy and very cold with snow at times, heavier in north and west, further accumulations of 10-15 cms possible there, 2-5 cms south and east. Winds NW 30-50 mph, lows reaching -4 to -6 C except -2 to zero in west coastal locations. Wind chills -10 to -15 C. Very icy roads.

FRIDAY ... Continuing windy and very cold with frequent squally showers of hail and snow, considerable accumulations possible but mostly in Ulster and Connacht, west Munster, parts of north, west Leinster where amounts will average 5-10 cms and reach 15 cms locally. Showers may mix with sleet near the outer Kerry coast. Highs for the day only -3 to -1 C in north (inland) and 2-4 C in southwest, 0-2 C in southeast and east. Some intervals of bright sun will also be hazardous because of glare off snow and ice at low sun angles. Winds WNW 20-40 mph with some higher gusts. Roads becoming very treacherous in many counties but with highly variable conditions too, travel with care if you can't avoid travel.

WEEKEND ... Bitterly cold to start with some clearing in the north late Friday night and lows generally -7 to -4 C but as low as -10 C in any northern valley locations under clear spots in the general overcast. Ice fog likely over central counties. Periods of snow may continue Friday night in some southern and eastern counties. Then on Saturday, snow likely to spread in or break out locally, heavier in the northeast at first, then becoming rather heavy in many areas, local accumulations of 5-15 cms both days, potential for near-blizzard or blizzard conditions with Dublin possibly near the higher snowfall zone that is likely to extend from about Meath to Laois and Tipps, but should emphasize that heavy snow could develop quite widely outside that zone too. Saturday night could clear in some northern and central counties with frigid temperatures possible (lows -12 C or lower in cold spots).

Sunday may also produce periods of snow in a northeast wind flow, and eventually, maximum snow accumulations could reach 20-30 cms. Some thunder-snow likely. Winds will increase at times to NE 15-25 mph blowing this snow around, in temperatures in the range of -2 to +1 C (could stay colder than that in parts of Ulster and inland Connacht).

MONDAY ... The above snowstorm to blizzard conditions may continue or may ease slowly, but in any case, there will be a lot of snow on the ground and temperatures near -1 C with potentially strong E to NE winds at times.

TUESDAY to THURSDAY ... Some snow could continue in the south, and flurries or freezing drizzle will keep roads icy in many areas, but this could be a somewhat drier period with breaks in the overcast and very cold temperatures at night as a result, lows may fall to -8 C or lower, highs will remain in the range of -2 to +2 C. It could become just slightly milder by Thursday, 2-4 C.

OUTLOOK ... I tend to discount any major suggested warmings but there is a chance of milder weather around Christmas, however, I think there is an equal chance of a further period of snow with the mild air held back to the southwest.

For those with an interest in weather in the U.K. or northern France for their travel plans, it seems quite possible that the snow in Ireland will break out over large parts of the U.K. as well, and may extend at times into northern France. Parts of central England are likely to see the worst of the snow there, 20-40 cms potential. Eastern Scotland may see some snow, but central Scotland and northern England could see bitterly cold overnight lows during the period, as low as -20 C in some places, but generally -10 C or lower.

Weather here today was cloudy with light rain and a high near 6 C (Wed 15th).

I may update the snowfall table later, but will maintain it for now.

Have looked at the available new guidance, mainly the 18z GFS, and while there are suggestions of a stronger storm system for late Saturday into Sunday, that could also bring in mixed types of precipitation for the southeast coast, I am not currently going to amend the forecast because I believe there is too much uncertainty about the details presented, and continue to think the actual evolution of this storm will be a bit further south and therefore with less tendency to mix precipitation over Ireland (this will be an issue across southern England perhaps).

As a result, no amendment to the current forecast is the call, and I await the verdict of the 00z models where I can compare any changes that four or five reliable players are picking up ... the situation is no doubt fluid and readers are cautioned that these are forecasts, not timetables (of course, timetables are forecasts too, perhaps I should say tide tables which tend to be virtually 100% reliable unless very strong winds interact with the ocean tides).

Friday, 17 December, 2010 _ 0650h
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ALERT continued for widespread heavy snowfalls spreading gradually from west and north to cover also east and south later today, then further outbreaks more concentrated on east and south over the weekend. Some risk of disruption and blizzard conditions at times. Very icy roads and anticipated travel delays or cancellations. Severe cold also, especially central counties overnight hours.

Situation update -- The very cold northerly flow is backing to NW'ly through the day, but will be reinforced by a fast-moving trough late today and winds will return to a more northerly direction. This trough will become the focus for snowfall to spread east beyond the current mainly sea-effect driven bands in the west and north. Particularly heavy snow bands are likely this morning around Mayo and eastern Ulster towards Isle of Man. Tonight the trough will promote bursts of heavy snow in the southeast. Saturday, another low likely to form off the west or southwest coast and move around the south coast towards Cornwall. This would set off periods of snow across the south. Following that, a stronger low likely Saturday night, moving past the south overnight and towards south Wales or southwest England Sunday, crossing southern England. This could set off very heavy snow in Ireland with strong northeast winds. Some further snow Monday, then gradual clearing, staying cold.

FORECASTS ...

TODAY ... Continued windy and very cold with heavy snow showers in parts of Connacht, Ulster, West Munster, inland north Leinster, and flurries elsewhere during the morning to early afternoon, amounts 8-15 cms heavier once again from about Mayo to Antrim. Accumulating snow in east and southeast only likely afternoon and evening, 2-4 cms by then.

Further east and south, morning will bring some sunny intervals with passing flurries or hail showers. Winds in general NW 25-50 mph becoming WNW 25-45 mph, backing in south only to WSW 20-30 mph late afternoon, mixed showers likely in Kerry and Cork at this point, with outbreaks of heavy snow further north across Clare and Galway spreading across the country during the afternoon and evening. Widespread icy road conditions.

Highest temperatures -3 to +1 C, except 2-4 in Kerry and Cork.

FRIDAY NIGHT ... Snow becoming rather heavy at times and spreading into the eastern counties while becoming more intermittent in the west, amounts of about 5-10 cms likely with heavier amounts this time in eastern counties and also across much of Ulster. Winds turning more northerly after midnight, with lows of about -3 C east to -7 C central and -4 C west. Widespread icy road conditions.

SATURDAY ... Periods of snow may become intermittent, with 5-8 cms further, very cold with light to moderate northeast to northwest winds, some sunny intervals could develop in the north and west, but highs only -3 to near zero C.

SATURDAY NIGHT & SUNDAY ... Renewed periods of snow becoming heavy across most of the country, with winds NE 25-45 mph in northern and central counties, somewhat variable and lighter across the south (although strong winds could strike there at times). Snow could mix with sleet near east or south coasts, but this may be quite limited. Snow amounts likely to be 10-20 cms but could reach 30 cms in some inland southeast counties and blizzard conditions are possible. Morning lows of about -4 to -7 C with daytime highs -3 to -1 C for most.

MONDAY ... There could be an extension of the snowfall period although becoming lighter, well into Monday with a gradual tapering off to drizzly light snow grains or freezing drizzle. Then it seems likely to clear late Monday with bitterly cold temperatures over the fresh snow. Temperatures on Monday similar to Sunday, -5 to -1 C.

TUESDAY ... With any clearing, Tuesday morning lows could be downright frigid inland, -12 C or even lower in parts of the inland southeast and Midlands, Ulster. Elsewhere, closer to -7 C ... afternoon highs in the range of about -5 to zero C, with some sunshine and some lingering ice fog or low cloud.

OUTLOOK ... Possible sleet or freezing rain that was entering the mix for the period Wednesday 22nd to Friday Christmas Eve, is now once again looking more like the chance of further snow, and there is now only a very slight chance for any significant thaw with some rain in the far south. This will all depend on the track of an Atlantic storm that seems likely to try to push the cold air back north to some extent, but is now being challenged by a wave swirling southeast from Iceland trying to phase in with that low. The most likely solution would involve light snow and freezing drizzle around Thursday night and continued cold into Christmas. Another storm looms for late Christmas into the 26th. At this point, we have to guess this one too may start to acquire a colder profile as we get closer to the time. But as of today, some models show this as a thaw with rain. We'll see how that works out.

Now, here's the updated snowfall chart, snowfall in cms.
Tonight refers to the period now to 0800h Friday, which may be one reason why Friday (0800-2400h) amounts appear reduced.

REGION ............ FRI ..... SAT ..... SUN ..... MON ..... TUES
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Ulster .................08 ...... 10 ..... 10 ...... 03 ..... 01

Connacht ........... 08 ...... 07 ..... 08 ...... 02 ..... 01

West Munster, Clare. 05 ..... 05 ..... 12 ...... 07 ..... 01

East Munster ......... 05 ...... 10 ..... 12 ...... 08 ..... 01

inland southeast ..... 06 ...... 10 ..... 25 ...... 10 ..... 02

Dublin/Wicklow/Meath. 04 ...... 10 ..... 20 ...... 10 ..... 02

rest of Leinster ......... 04 ...... 12 ..... 18 ...... 07 ..... 01

The weekend snowfalls may become blizzard-like in some cases, whether they are technically a blizzard or not may depend on wind speeds. But coastal parts of the east and south could see some mixing so that while it may snow the same amount, not all of the snow will cover the ground to same depths near the coast especially southeast Wexford and outer parts of Cork coast.

The situation is quite fluid and range of possible outcomes is something like half the above to 50% more than above. Local snowfalls Sunday could reach 40-50 cms on higher parts of Wicklow and Dublin mountains.

Updates as required.

Saturday, 18 December, 2010
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ALERT for heavy snow in eastern Ulster spreading southwest to north Leinster this morning. Local amounts of 5-15 cms possible. This may either miss Dublin to the north or skim past giving trace to 3 cms in Dublin. Another area of possible heavy snow would be west Munster, and isolated falls in Connacht. These are more showery hit or miss situations with 3-5 cms possible. Also, ALERT for widespread icy roads and some very difficult travel in Connacht and Ulster, consult the forum road threads and other resources for updates on travel.

Situation update: The heavy snowfalls in the north, northwest and parts of the southwest are becoming more localized as the strong sea-effect is being replaced by meso-scale troughs. The south central, southeast and eastern counties that escaped most of the snow may remain dry today in most cases, but could see outbreaks starting late tonight or Sunday, as low pressure currently moving past the west coast circles around to the south. Models are giving widely different tracks and intensity, so my forecasts will have to be on a consensus, but I think that there is potential for some heavy outbreaks later today around Cork and Kerry, and then spreading slowly further east across the south into the southeast on Sunday, with reinforcements on Monday and possibly yet again on Tuesday. The snow mentioned in the alert for eastern Ulster is likely to break up later today rather than moving across north-central Ireland but it is heading for counties such as Longford and Westmeath before totally disappearing.

In the longer term, most of the guidance points to a dry trend for the central and northern counties spreading more to the south after this series of waves moves past, then for another frontal system to try to move milder air into Ireland on Christmas Day. Chances appear about one in three for success on that venture, and more than one in three for a snowy episode as a result, while another outcome (less than one in three) would be for the cold to remain dry and hold the front back entirely. We're entering a pattern now where any half-formed low near south coast of Ireland could gain energy and turn into a sizeable snowfall event or even a snowstorm. And this applies to a considerable time well into the future as North America's storm track looks to be ejecting lows every 3-4 days into the latitudes south of Ireland, all of these heading generally towards France. Either one would eventually swerve a bit north bringing milder air and rain, or one could explode into a powerful storm that would be a blizzard-like snowstorm. In this pattern, it is really difficult to say which of several storms might do one of those two things, but it seems likely that in general, it will stay cold with this frontal boundary often just to the south. Sorry about the uncertainty, but such is the nature of this atmospheric "science." Even on the 48-hour time scale, systems are appearing and disappearing from models, such as the projected major storm for southern England on Sunday -- now more or less downgraded to a weak event. I'm keeping my eye on Monday when there's an energy peak that could work with the low then located south of Cork.

FORECASTS:
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TODAY ... For most regions, partly sunny and very cold, some drifting ice fog in valleys, icy roads, and light east winds (light southerly in west Munster). Highs for these regions about -2 C. However, some areas of snow are likely too. One will extend from parts of Down and Louth towards Meath, Westmeath, Cavan, Monaghan and Longford, but could also brush Dublin and Kildare. Heavier amounts are likely in Ulster this morning (5-10 cms) with lighter amounts as this cluster breaks up moving southwest at mid-day. There may be a chance of streamers for Dublin and Wicklow later today too, with local 3-7 cms amounts possible. Another area of localized snow could develop from Cork (city) west to Kerry, with 3-7 cms locally in this as well as some sleety showers close to the coast. There will also be scattered remnant sea-effect snow showers drifting around in parts of Connacht and West Ulster. Amounts there would be confined to small areas, 2-4 cms.

TONIGHT ... Clear and very cold in some central and northern counties, with just isolated flurries mostly near the coasts. Lows -7 to -12 C. Some ice fog developing. Cloudy in the south and southwest, parts of the west near the coast, with outbreaks of snow likely, 3-7 cms for some areas, affecting west Munster and possibly spreading to East Munster. Also a slight risk of snow showers near the east coast localized but heavy in a few spots. Lows in these regions about -4 C.

SUNDAY ... Outbreaks of snow likely across the south, possibly heavy in parts of Munster, later spreading to inland southeast, 5-10 cms with higher potentials. This may be somewhat patchy and intermittent with fog and coastal drizzle added, as winds come in from the SE at 15-25 mph. Further north, cloudy with some sunny breaks more frequent in the north, cold, highs generally -1 to +2 C south, to -3/-1 C further north. Light winds in many areas of the north, but some risk of coastal flurries.

MONDAY ... Once again, snow possible across the south and southeast, heavier in the inland southeast, 5-10 cms possible, winds E 15-25 mph. The temperature regime on Monday will probably repeat Sunday's for most regions, and it should remain dry in the northern two thirds except for some widely separated flurries in the northwest. Highs generally -3 to +1 C.

TUESDAY ... A few further flurries in the southeast, chance of sleety showers near the west coast, staying rather cold in the daytime, but bitterly cold for some during the early morning. Highs generally -2 to +1 C.

WED-THURS ... Dry and cold, some sunshine each day, lows could reach -15 C over snow and -7 C in most areas, highs near -1 C. Some snow possible by late Thursday.

FRIDAY (Christmas Eve) into SATURDAY (Christmas Day) currently looking unsettled and possibly a bit milder, but there is a risk of snow or freezing drizzle. For now, would say chances about 2/3 that it would stay cold and be a white Christmas from the earlier snow if not from falling snow.

OUTLOOK ... see situation report above.

The weather here today (Friday 17th) was sunny and the high was about 7 deg C. Expecting rain tomorrow.

As snowfall amounts are posted in the forecasts above, I will leave out the table for now, partly because it would require even more divisions to handle all the expected variations, but in general, it looks like the area around Athlone may stay closest to dry through the period, and areas from Cork to Waterford to Carlow might see the most snow during the period, once today's Ulster snowfall dies out.

Updates may follow ... but I can safely say that I may be asleep from 0800 to 1500 so in that time frame, would consult the forum discussion for updated forecast thoughts.

Sunday, 19 December, 2010
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We can be fairly certain that it will remain cold until Christmas Day, but the prospects for further snowfalls remain quite uncertain. Most model guidance continues to indicate weak systems that do not spread much if any moisture inland, away from the southwest. However, two things could go wrong with that dry scenario, first there could be stronger development as hinted at on one or two of the models; and second, there could be outbreaks of snow where dry weather is indicated as the air inland is intensely cold while the air along the south coast is holding a temperature near 2 or 3 C. Also there is the issue of streamers moving inland from the Irish Sea at various times, which seems likely to happen somewhere on a daily basis. Not an easy forecast scenario for snowfall, and then there is the looming question of a possible breakdown to milder weather, which several models insist will happen on the 25th, while others hold firm to the colder regime. I'll keep my opinion a surprise to the end of the forecast.

TODAY ... Widespread ice fog inland, low cloud or mist gradually breaking up to give some periods of wintry sunshine, icy roads very likely ... some snow breaking out across parts of Galway, Clare, Kerry (inland) and Cork (inland), with rain or sleet along the outer southwest coast. By afternoon and evening, some of this snow could spread to other parts of the south and southeast. Watch for updates, this is not yet a "sure thing." But snowfall amounts where the snow does break out, could exceed 5 cms in places. Also there will be further chances for streamers on the east coast, affecting parts of Leinster and Ulster. Highs today should average -2 C with colder readings in north central counties, milder along the south coast (to 5 C on outer coast). For Cork city, a tricky forecast, mixed precip may move in and be divided by elevation as temperatures hover in the 1-2 C range. But there is potential for heavy snow in places around county Cork later on, as there will be during the whole day in Kerry (inland). Winds today generally rather light easterly but SE backing to E 15-25 mph south coast.

TONIGHT ... Some clearing, bitterly cold except for the southern counties where rather cold, lows generally -8 to -15 C (not quite this severe in some coastal areas around the east, north and west) while -2 to -4 C south, where a continued risk of snow will exist (updates may change this to amounts forecast). Streamers from the Irish Sea could give local 2-5 cm accumulations.

MONDAY ... Following another bitterly cold night with local ice fog and lows in the -15 to -8 C range (and again, milder in the south, near -4 C), the day will be cloudy with some sunny breaks, and possible outbreaks of snow in the east and south. There will be moderate E to NE winds at times, and the daytime highs will be in the range of -4 to +1 C.

TUESDAY ... Bitterly cold with ice fog to start, lows -16 to -8 C inland, closer to -4 C in the south, with risk of snow breaking out at times during the day, highs only around -3 C.

WEDNESDAY and THURSDAY ... Continuing very cold, some clear spots in central and northwest counties, where lows could reach -15 C each night, ice fog in places, while the east will see stronger NE winds and a risk of heavy snow in streamers or organized bands, highs each day around -2 C.

FRIDAY (Christmas Eve) ... Cloudy, cold, possible snow at times, but also some sunshine in the north. Temperatures remaining very low and similar to the previous days, but perhaps a bit milder in the south and southwest.

SATURDAY (Christmas Day) ... At this time, the odds seem to favour a cold day with snow but sleet or rain are possible in the southwest. The cold spell could break down at some point, but model performance on this question has been erratic to say the least, so the conclusion is, only a gradual warming trend seems likely and it could be reversed at any point.

Watch for updates today and visit the discussion forums for all the latest thinking, especially between 0900 and 1600 when I am likely to be off duty (although it's always a good idea).

The weather here on Saturday (18th) was wet and chilly with a mixture of rain and wet snow, no accumulation at my elevation but probably sticking just a bit higher up. The temperature was steady around 2-3 C. It remains quite cold across most of North America although not too extreme in most places. A snowfall of several inches is likely across the lower Great Lakes on Monday and Tuesday.