Snow star crystal 1.5mm diameter grown on an electric needle: Photo Ken Libbrecht.

Llansadwrn (Anglesey) Weather:
Snowdonia Snowline Report

Logo: Llansadwrn Weather - Melin Llynnon, Ynys Môn.

Snowdonia Mountains Winter 2009 - 10

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Snow on summits of the Snowdon Horseshoe on 4 January 2010.



No snow.


No snow. Snow fell on Cairngorm Mountain on the 4th.


The median date for the first snowfall over the past 30-years was on the 2nd and was 5 days late this year with light snow on the mountaintops on the morning of the 7th. Light snow on Cairngorm Mountain disappeared by the 20th, but a sprinkling returned on the 21st. On the morning of the 22nd there was a sparse deposit of ice precipitation (probably hail) seen around the summits of Carnedd Llewelyn and C. Dafydd, Snowdon was obscured in cloud; there was a good covering of snow on Cairngorm. Patchy deposits of ice precipitation were seen around the summits on the 25th to 28th. Overnight 28/29th snow fell as low as 500 ft and there was light to moderate (10 - 15 cm level) snow lying at 1500 ft. More snow fell during the day with blizzard-like conditions above 2500 ft. This left snow drifts of 5/6 ft high on some slopes of the Carneddau. On the 30th while the snowline had retreated to 1800 ft and cover mostly light, there were moderate accumulations on some slopes with drifting. Snow showers continued around the summits.


On the first there was snow lying at 1800 ft with some as low as 1200 ft in places. Snow at 1800 ft on the 2nd, but patchier at lower levels, some patches were deep, an indication of previous moderate windblown falls. By the 3rd there had been some thawing, but there was good cover at 2500 ft with thinner cover below the Black Ladders at 1800 ft. There were more snow showers during the day and on the morning of the 4th there was snow lying at 1800 ft with some as low as 1200 ft including on the cliffs around Cwm Idwal. On the 5th there was some snow lying at 1800 ft in places, but on the 6th snow was mostly broken except for some steep north-facing slopes at 2800 ft. From the 7th there were frequent snow-patches remaining at 2500 ft from deep drifts formed on 28/29th November. Still frequent the patches some in elongated streaks and gullies had reduced in size and disappeared below 2800 ft by the 12th. On the 14th sleet and wet snow fell above 2500 ft leaving a thin deposit, particularly on Snowdon by the end afternoon, but had disappeared by the morning of the 15th. Patches were persisting on the 16th when overnight 16/17th there was fresh snow as low as 1800 ft and light snow lying at 2000 ft on NE-facing slopes of the mountains on the 17th, especially C. Dafydd and Snowdon. Slight snow at 1200 ft on the 18th with light to moderate accumulations at higher levels. Further snow overnight 18/19th gave light to moderate accumulations above 2000 ft with slight deposits around 300 ft . Ponies foraging in snow on the Carneddau Mountains. On the 20th snow was lying at 2000 ft with ice deposits as low as 100 ft. There were variable deposits overnight in showers with some moderate accumulations in places at higher levels. With frequent snow pellet and snow showers during the day and early on the 21st variable light deposits were as low as 600 ft with snow continuing to accumulate on the summits. Very icy at all levels on the 22nd and 23rd, light snow in showers across the range leading to further accumulations of 10 - 15 cm in places at higher levels in central Snowdonia including at Pen-y-pass. More snow fell generally settling above 500 ft during the evening of the 23rd led to further accumulations with a little drifting in places. On the 24th and 25th snow was lying at 800 ft, below in some places, but rising temperatures and rain at low levels late on the 25th led to some thawing overnight even at 2500 ft. By the 26th the snowline had risen and was 1800 - 2000 ft centrally on the Carneddau, but there was some snow as low as 1200 ft including Cwm Idwal. There was more snow from the 27th to the 30th, especially on summits in the east of the range over 1000 ft and in the west over 2000 ft, that led to moderate accumulations in blizzard conditions. On the afternoon of the 30th with snow falling all day snow was seen as low as 600 ft just below the cloud base on the eastern Carneddau and was lying at 600 ft on the 31st. Most snow at lower levels was east of the Nant Ffrancon Pass to the west the snowline averaged 1000 ft. Snow on the Carneddau was up to 15 - 30 cm deep in places with wind blown drifts up to 6 ft. The month had the most days of snow since 1999.


The month began with snow lying widely as low as 600 ft with moderate to large accumulations at higher levels. On the 1st snow was lying 15 - 30 cm deep at Pen-y-pass and Llyn Llydaw where the Fell Runners Association held a race. Runners made their way through 30 cm snow in places along the Miners' Track past the frozen Llyn Teyrn, with snow on the ice, to the unfrozen Llyn Llydaw. Light to moderate snow (5 - 10 cm) was lying from Pen-y-gwryd (most) to the frozen Llynnau Mymbyr (least). Further snow overnight on the 2/3rd added to the snow depth within the around Snowdon Horseshoe, the summits of Y Lliwedd, Yr Wyddfa, Crib y ddysgyl and Crib Goch, including the rock faces, were 'glistening white' with snow and ice, in the sunshine. There were more accumulations on the summits of the Carneddau around Drum, Foel-fras and between C. Llewelyn and C. Dafydd. On the 3rd there was light snow lying on northern slopes as low as 400 ft centrally beneath the Carneddau and to the East, including Llandegai, Bethesda and at Ogwen Cottage with Llyn Ogwen and Llyn Idwal frozen. On the western range of mountains snow lay at 800 ft around Llanberis and on Moel Eilio. MODIS TERRA image courtesy of the Rapid Response Team at NASA/ GFSC. On the 4th there was little change in the snow and with overnight temperatures in places down to at least -6C there was frost and ice at low levels persisting in valley bottoms and shaded slopes. The slopes of Carnedd Llewelyn were well covered Snow cover on Carnedd Llewelyn on 4 January 2010. . In the Llanberis Pass snow was sparse along the road below 1000 ft, but icicles were frequent and waterfalls frozen sheets of ice. Further snow showers on the 5th light at low levels turning prolonged and moderate to heavy at higher levels in strengthening winds. Click for larger image. Snow to sea level on Anglesey, on snow lying on Rhosneiger beach by the afternoon. On the 6th snow was lying thinly in places to sea level and there was 3 cm in parts of central and SE Anglesey. Snow showers continued through the day mostly around western summits and later coastal areas of Anglesey and Lleyn. Some snow was still lying at low levels on the 7th with little change on mountain slopes. There was no more snow by the 8th, but with low temperatures persisting despite sunshine there was little change in the amounts on the ground at higher levels. There were some snow showers on the summits on the 9th and light snow during the day on the 10th above 500 ft with drifting in places. It was snowing generally with deposition as low as 400 ft (light and wet) on the morning of the 11th. More snow overnight 12/13th with again snow lying at low levels and in Llanberis (the road to Pen-y-pass was closed), Llanfairfechan and parts of NW Anglesey and Lleyn. Light snow fell most of the day on the 13th and although there was thawing at low levels snow continued to accumulate at higher levels although fresh amounts were small. An avalanche at Aber Falls was searched for 3 h by 30 members, with dogs, of the Ogwen Valley Mountain Rescue Team after walkers had found a head torch nearby. Little change was seen on the 14th, snow on the Carneddau showed signs of wind blow with thinner and deeper areas, while sparse areas on western slopes had begun to thaw by afternoon. Rising temperatures in warm sector air at midnight and rain by the morning f the 15th brought some more thawing, but deep areas of snow remained on the Carneddau by afternoon. Although the snow cover was broken there was more than 50% cover above 1500-1800 ft on the N slopes of the Carneddau from the 16th and frequent deep snow-patches persisting in gullies and from drifts as low as 350 ft on the afternoon of the 17th. There was much less around Llanberis and Snowdon. On the 20th with large patches persisting above 600 ft on the Carneddau light wet snow fell above about 2000 ft and was lying on the 21st. From the 22nd patches, large above 100 ft but smaller as low as 600 ft, persisted. A little snow fell overnight on 24/25th giving a slight covering above 2000 ft centrally on the slopes and cliffs of the Carneddau, and around Snowdon at 2500 ft. Freezing levels continued to be as low (1000 ft) and there was little change up to the morning of the 26th. Rising temperatures on the 27th led to thaw of sparse lying snow and small patches, but had little effect on the area of some larger snow-beds persisting on the 28th. Rain turned to snow 28/29th with accumulations over 2500 ft and a little on the ground at 1200 ft. Snow and snow pellet showers continued through the day around the summits and began again at low levels during the evening. On the 30th there were with sprinklings of snow and snow pellets to sea level, although distribution and amounts were variable due to the showery nature of the precipitation. There was a covering in places around Snowdon and on the summits and northern slopes of the Carneddau above 2000 to 2500 ft. More snow showers moving in off the Irish Sea during the evening and overnight 30/31st left 1 - 2 cm of dry snow lying in places as low as 150 ft.


On the 1st snow was lying thinly as low as 400 ft with remnants in places at 300 ft. With rising temperatures on the 2nd snow thawed up to 2500 ft, but the deep snow-beds remained above 1000 ft with small patches as low as 600 ft. On the 3rd snow was lying at 2500 ft; during the morning rain and sleet at low levels fell as snow above 1500 ft, but by afternoon had thawed. By the 4th only a limited area above 2750 ft on north faces and summits had >50% cover, but large snowbeds remained. There were further sprinklings of snow on the 9th and through 12 - 14th these usually soon disappeared on lower slopes. On the 16th there was more general snow to low levels, especially on eastern Carneddau 500 ft, Glyders and Snowdon 1500 ft. On the morning of the 17th snow was lying above 1500 ft with large snow-beds (old) persisting as low as 800 ft. On the 18th light to moderate snow fell above 2500 ft and, with showers on the morning of the 19th, light snow was lying at low levels and for a while above the high tide mark on Rhosneiger Beach. With further snow, sometimes heavy and prolonged in showers during the day, 5 - 10 cm snow fell in several places and amounts continued to accumulate at higher levels. More snow in showers overnight 19/20th, with snow again lying in places at low levels, with moderate to heavy accumulations over 1000 ft. A frontal low developing over the Irish Sea brought more snow overnight 20/21st, moderate to heavy on the summits and light to 200 ft with sprinklings to almost sea level. There was snow lying as low as 400 ft on the 22nd and 23rd becoming broken below 2500 ft on the 24th with patches remaining as low as 400 ft. There was little change on the 25th to 26th, when there were showers of ice precipitation during the afternoon. Up to the 28th there good cover remained on summits and ridges with broken snow cover as low as 1200 ft in places (including Cwm Idwal). Large snow-beds persisted on lower slopes of the Carneddau some smaller patches as low as 400 ft particularly near Abergwyngregin.


On the 1st there was good snow cover above 2000 ft and on the summits of the Carneddau and around Snowdon. Snow-beds were persisting around 1000 ft with smaller patches as low as 400 ft. There was little change up to the 10th with cover remaining around the summits and snowline (50% cover) rising to 2500 ft. Some large snowbeds remain while those at 400 ft had become fewer and quite small. From the 11th lying snow was less and patches, though smaller, were still to be seen around 400 ft on the 14th. On the 16th there was unbroken snow cover still on the tops of the Carneddau, broken snow >50% cover was mainly above 1750 ft on northern slopes, but on S-facing slopes snow was sparse. Most of the smaller patches at low level began to disappear quickly and by the 18th the lowest were around 1000 ft on N-facing slopes. Rapid thawing of snow on the summits took place during the day. On the 21st there was broken snow on the tops and cliffs of the Carneddau with patches as low as 1000 ft on N-facing slopes. From the 25th remaining patches were at 1800 ft and on the 29th there was a little fresh snow on the summits. Overnight 30/31st heavy precipitation moved S over the Irish Sea falling as wet snow on the mountains above 600 ft. Mostly light on lower slopes, but in places falls of 10 cm or more were reported with moderate amounts on the summits of the Carneddau.


On the 1st there was light snow lying at 600 ft on the lower slopes of the Carneddau, but was as low as 400 ft in places. By the end of the afternoon the snowline had risen to about 1500 ft with small amounts remaining as low as 600 ft and on the sides of the Nant Ffrancon Pass and at Ogwen. In evening sunshine a deep white covering was seen on the summits of the East of Carnedd Llewelyn. There was a little fresh snow on the 2nd and 3rd lying as low as 2000 ft between C. Llewelyn and C. Dafydd and as down to 1200 ft near Cwm Idwal. There was a good covering on the summits between C. Llewelyn and Penyrole-wen with patches at 800 ft. By the 6th snow had begun to disappear rather quickly with some large patches remaining thereafter between 1500 ft and 2000 ft depending on location. Snow-patches on S-facing slopes soon disappeared, but on the 27th there were small patches remaining as low as 2000 ft under the Black Ladders with several larger snow-beds remaining under N-facing cliffs of the Carneddau and E-facing slopes near Tal-y-fan.


The month began with a few persistent snow-beds around the summit of Carnedd Llewelyn, large patches on the north-facing cliffs to the East, smaller gully patches on the Black Ladders about 2500 ft with remnants under C. Dafydd. On the morning of the 3rd there was a sprinkling of fresh snow on the summits across the range including Y Garn and Snowdon. There was a little left on the NE-facing slope of C. Llewelyn by the end of the afternoon. Large snow-beds remained on cliffs and gullies at 2750 ft, others at 2500 ft under Ysgolion Duon. A late fall of snow on the Carneddau Mountains.On the 11th showers moved in off the Irish Sea on a moderate N'ly giving a late sprinkling of snow as low as 1500 ft on the Carneddau somewhat heavier on higher cliffs and summits of C. Llewelyn, C. Dafydd, Penyrole-wen and Mynydd Perfedd. There was snow at 1200 ft in Cwm Idwal and a little on Yr Wyddfa. There were further wintry showers overnight and early on the 12th leaving sprinklings of snow mostly around the summits of Foel-grach and Carnedd Llewelyn. There was still a sprinkling of snow on the tops of C. Llewelyn and C. Dafydd on the morning of the 13th, remaining on C. Dafydd in the afternoon, with large old patches in gullies and N-facing cliffs. A snow-patch persisted below Ysgolion Duon about 2500 ft until the 28th while large snow-beds remained on the cliffs about 2800 ft between Foel-grach and Carnedd Llewelyn beyond the end of the month.


Snow-patch at Y Ffoes Ddyfn on the 20th June 2010. (c) Gordon Perkins. On the 2nd several large snow-beds were present around 2850 ft on cliffs between Foel-grach and Carnedd Llewelyn. On the 3rd at least 2 patches were seen from the Conwy Valley on the E-facing side of the Carneddau (not visible from my station). Though becoming smaller by the 8th two patches between Foel-grach and C. Llewelyn remained The remaining snow-patches on the Carneddau. . By the 11th the smaller patch had almost disappeared, but the larger was persisting well . An unconfirmed patch on Snowdon on the 15th was reported. Reduced in size to a bucket full the last patch on the Carneddau in view from Llansadwrn melted on the 21st, a remarkably late date in the current climate. Another patch unsighted from Llansadwrn, on the lower SSE-facing slopes of Carnedd Llewelyn just over the ridge in Y Ffoes Ddyfn 'The Deep Cut' at 2950 ft, was 60 ft long and 12 ft wide on the 20th (see photo left). Seen again on the 25th, reduced in size and fragmented with the largest still 30 ft long and 10 ft wide The larger of the snow-patches in The Deep Cut. , probably melted after 'warm' overnight rain on the 28/29th. These patches were probably the last surviving in Wales and England in 2010; snow persists much longer in the Highlands of Scotland with patches going at least into August.




Snowdonia snowline current histogram.