Thursday, 14 January, 2010
A rather weak low is moving across the southern Bay of Biscay into southwest France and throwing off some mid-level moisture that is being swept into weak waves near south coast Ireland and southeast England. These will continue northeast dropping very light rain or melting snow, but will not amount to much, while a more organized area of rain develops in central France from the lows, turning to mountain snow.
Meanwhile, a stronger low is forming up north of the Azores, and will ride a rapidly strengthening jet stream northwards, bringing a surge of mild, moist air towards Ireland on Friday morning.
TODAY will be cloudy with some sunny intervals possible, and scattered light outbreaks of rain or melting snow, in light winds becoming SSW 10-20 mph later this afternoon. Highs will be about 5-7 C for most. Fog will continue to be found over melting snow packs in many parts of Ireland but especially the inland northwest, parts of the Midlands, and over higher parts of Wicklow and Dublin. Thawing will be quite gradual today but the early stages of flooding may be encountered in one or two places.
TONIGHT will become foggy and rather windy with any early frost likely to dissipate around midnight. Temperatures will then rise towards 5 C in the south and 3 C in the north. Winds will become SSE 20-40 mph, and rain may be intermittent but could turn heavy in a few spots.
FRIDAY will become milder still but with widespread heavy rain and melting snow, many areas will see dense fog, as well as strong south winds 30-50 mph, temperatures steady in the 8-10 C range over lower ground, 4-7 C higher up. Winds could be very gusty in Kerry and Cork (60 mph at times). Snow will melt steadily and there is likely to be some flooding, getting worse by Friday night as higher level snow melt reaches lower elevations.
FRIDAY NIGHT will continue windy and very mild, near 8 C, with further rainfalls bringing totals to 30-50 mms. There may be some thunder. Flooding could become severe in some parts of Ireland near higher terrain, and there is a hazard of mudslides and possibly a few highland snow slides or minor avalanches.
SATURDAY should see improving weather but the flooding will continue. Skies should clear gradually from west to east with diminishing SW winds turning more to the W by late in the day, as temperatures stabilize near 7 C, falling to 2 C by evening. A secondary line of showers with hail may develop in Connacht by afternoon, with strong wind gusts.
Not all of the highland snow will melt; what's left by the weekend may seem inviting for a drive or hike if the weather improves, but I would caution anyone venturing up high that snow may be very unstable, and there could be snowslides and mudslides or flash floods in various locations.
SUNDAY-MONDAY should bring a rather cool, sleety or drizzly period again as fronts die out while a slow seep of colder air from the North Sea pushes towards a moderate SE flow continuing to draw on 5-7 C air with its origin in France. Winds will be SE 20-35 mph for much of this period Sunday and Monday will at least be the best days in a while to get around with much of the lowland ice and snow gone, as long as mud, debris or floods don't block your path. There may be another interval of rain later Monday into Tuesday morning. Heavy showers may develop at times Tuesday with gusty S to SW winds in western districts colliding with the SE flow continuing further east.
TUESDAY night or WEDNESDAY will see a colder spell returning, with possibility of east coast snow and temperatures near freezing. I am going to leave these details partly to other threads today, and partly to later forecasts, because I want to keep the focus on this high impact Friday-weekend event. There is some chance that this may sweep on by Ireland with only a brief impact. In the longer term, plan around a possible warmer spell of weather near the end of the month, that could turn very windy by late 30th or 31st. With any sort of luck, this may not be overly wet, just windy and showery.
Today (Wed) has been yet another very mild, drizzly day here with another near-record high of 13 C.
Watch for updates all over the forum, as I may be turning in soon ... sleep deficit after the big weather days.