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 2003 - 04

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  • Snowline histogram


    The first cool weather of the autumn on 4th brought wintry showers across the summits where temperatures were between 1-2C early in the day. There were snow showers early on the 5th that whitened some slopes but soon melted. The weather turned colder again on the 19th and there were snow showers on most summits (including Carnedd Llewelyn and Yr Wyddfa) on the morning of the 20th. Overnight light snow fell across most high ground and was lying as low as 1500 ft on the morning of the 21st. Wet snow was lying as low as 1000 ft early on the morning of the 22nd but, except at the highest levels that remained below freezing, most soon melted. On the 23rd snow was lying above 2700 ft with a good cover around the summit of Yr Wyddfa, Crib Goch and Carnedd Llewelyn but soon became patchy. Several more days saw further ice precipitation around the summits with a few patches, on north facing slopes above 3000 ft, surviving to the end of the month.


    Last year (2002) saw no lying snow in November and the return of warm weather this year melted the few remaining snow patches on Carnedd Llewelyn, by the 5th, when temperatures on Yr Wyddfa summit reach 8C during the day. But on the 16th and 21st there were showers of ice precipitation, but little snow accumulated until the 22nd when slight amounts were seen on Carnedd Llewelyn and Yr Wyddfa. Slight snow accumulated on the Glyders and above the Idwal slabs on the 24th. By the 26th it was colder and, with the return of subzero temperatures on the summits, there was light snow cover generally around 2800 ft, and as low as 1000 ft for a time near Ogwen Cottage and the Nant Ffrancon Pass. After one of the coldest nights of the month snow was still lying thinly at 2700 ft on the 27th but thereafter retreated. At the end of the month temperatures reached several degrees above freezing on the summits. Only scattered patches remained in a few gullies, especially on the N side of Crib Goch, with only transient sprinklings seen from time to time after showers.


    Remnants of snow disappeared in milder weather at the beginning of the month. Apart from a few flurries around the summits it was the 15th before some lying snow was seen around the summits but this soon melted. It was not until the 20/21st that significant snow fell and lay generally at 1800 ft and down to 1200 ft including the Nant Ffrancon Pass and in Cwm Idwal. By the 22nd there was lying snow as low as 1000 ft but with temperatures rising again this too had melted by the 24th. Following heavy rain on 25/26th colder weather returned to give a sprinkling at 1600 ft and as low as 1200 ft in places. The 28th saw more snow and as low as 800 ft and by the 29th there were some moderate windblown accumulations above 1500 ft some cover lasting to the end of the month.


    It was not cold enough in Snowdonia for the heavy precipitation on the 31 December/1st of the month to fall as snow as it did elsewhere. As a result by the 2nd snow had become sparse above 2100 ft and had no continuous cover except around the summit of Yr Wyddfa. Snow persisted in similar amounts and altitudes until the 5th when warm sector air again led to rapid thawing. Snow patches, mainly in gullies, were persistent and seen on the morning of the 7th despite mild temperatures. Fresh snow was lying at 2000 ft on the 9th but was at 1200 ft in places including Cwm Idwal but again most soon melted in mild temperature. Deeper patches mostly in gullies persisting at least until the 11th. During the afternoon of the 12th it turned colder and ice precipitation was seen at 1600 GMT falling on summits at 2700 ft. On the 14th there was variable lying snow about 2200 ft but as low as 1500 ft in places. During the day there was moderate snow (8 cm) reported in parts South Wales and parts of S Snowdonia (2 cm). On the morning of the 15th the snowline on the Carneddau Mountains was 1600 ft. More snow fell overnight on the 16/17th and was lying generally at 2250 ft (down to 1650 ft) on the 17th. Some moderate accumulations in places were still lying on the morning of the 18th before the weather turned mild once again during the day melting most if it. Small patches of snow remained until the 25th when colder weather brought frequent snow showers on the 25th. By afternoon there was a good covering on Foel-fras, Carnedd Llewelyn and Crib Goch. On the morning of the 27th, with snow showers coming in off the Irish Sea on a northerly breeze, there was light snow at 2000 ft and was settling near the A5 at 1000 ft at Ogwen Cottage. Snow fell widely at low levels on the afternoon of the 28th as an active cold front moved S. On the morning of the 29th thin snow was lying sparsely in places as low as 400 ft with the general snowline on 1200 ft. By the end of the month rapidly rising temperatures and heavy rain cleared the snow.


    Cold weather returned on the 7th with wintry showers at low levels; fresh snow was seen above 2800 ft in the afternoon. On the morning of 8th there was thin snow at 2000 ft becoming slight to moderate in places above 1500 ft by the 9th. A return to mild weather led to rapid thawing and only traces were left on the Carneddau by the 11th, but there was a little more around Crib Goch. Occasional flurries on the 14th and 16/17th left sprinklings of snow on some summits. With temperatures again around freezing on the tops a sprinkling of snow was seen around Carnedd Llewelyn on the afternoon of the 18th. Snow showers on the 22nd left sprinklings around Drum, Foel-fras and Carnedd Llewelyn, but hardly any elsewhere, and with freezing temperatures on the summits was still there on the 23rd. On the 25th fresh snow was lying at 1500 ft and down to 1200 ft in the Nant Ffrancon and Llanberis Passes. In the afternoon wintry showers were sweeping across Anglesey and on to the mountains under cumulonimbus clouds. Snow pellets were frequent and there was a fall of conical shaped 10 mm diameter pellets in Llansadwrn at 1740 GMT. At 22 GMT snow showers were heavy and leading to moderate accumulations at higher levels. Further snow on the 26th from 0720 GMT to 1130 GMT led to up to 17 cm of dry snow across Anglesey and moderate to heavy accumulations in places on the mountains. There was snow down to sea level on Anglesey and parts of Gwynedd. The temperatures given by the Snowdon AWS at 09 GMT was -6.7C while the maximum in Llansadwrn during the day was only 0.9C. There was severe disruption to road traffic in North Wales during the morning but was hardly any better in the afternoon. Dry crisp snow was still lying on the mountain summits and at low levels on the morning of the 27th. After a sunny morning there were frequent snow showers across the summits. There was plenty of snow in freezing temperatures on the summits on the morning of the 28th, this lasting until the end of the month.

    Snow showers driven by a strong NE'ly wind (left to right) move across the Snowdonia Mountains on the afternoon of 27 February 2004. From the left Carneddau, Nant Ffrancon Pass with the summit of Tryfan, Mynedd Perfedd and Elidir Fach with Glyders behind, Llanberis Pass and Snowdon on the right.


    Snow was lying generally on the mountains at 600 ft on the 1st, but in places including the SE corner of Anglesey still as low as 98 ft on slopes with a northerly aspect. Most of Anglesey and slopes with a more southerly aspect were clear of snow. Temperatures on the summit of Yr Wyddfa were still well below freezing (-6.8C at 09 GMT). On the 2nd snow was still lying at 400 ft; on the 3rd with snow at 800 ft early in the day snow was falling around the summits (Yr Wyddfa AWS -1.5C at 09 GMT). By the end of the day a slow thaw had set in and by the 4th snow was much sparser (2500 ft) and patchy (1000 ft). On the 6th there were still plenty of snow patches, some larger snow beds and deep gully stretches, as low as 1000 ft. With freezing temperatures on the summits there were snow flurries during the morning. These remained largely unchanged, with addition of fresh snow on Snowdon and Carnedd Llewelyn on the 7th, as seen on the 8th. Snow cover remained unchanged, with occasional showers on the summits, until the 11th when there were intermittent slight falls during the day even at low levels. On the 12th a sprinkling of snow was lying as low as 600 ft but I had a report of it being near the shore at Abergwyngregin. The 13th saw some more snow showers depositing snow at 1000 ft on the Carneddau and near Lake Ogwen but subsequent rising temperatures and rain melted much of it by the 14th. Patches of snow persisted with occasional wintry showers to the 18th, but warm rain on the 18/19th led to further thawing of the remnants. On the 22nd there were just a few patches seen on the Carneddau and Snowdon before fresh light snow fell on Carnedd Dafydd during the afternoon. Temperatures on the summits kept below freezing in the succeeding days; the snow persisted and was still lying above 2800 ft on the morning of the 26th before there was much thawing. From the 27th patches persisted until the end of the month.

    Snow on 28 February 2004. View is looking SE across Llyn Padarn into the Llanberis Pass. Snow in the Llanberis Pass on 28 February 2004. View is looking W at the slopes up to Clogwyn. Mountain snow on 28 February 2004. Yr Wyddfa summit (3560 ft) and Crib-y-ddysgyl (3496 ft) are just obscured in cumulus cloud. Lliwedd is on the left and Crib Goch on the right.  Snow on the mountains on 28 February 2004.

    Snow cover over Wales with line of showers on trough in Cardigan Bay. NOAA 16 image at 1237 GMT on 27 February 2004. Snow cover on Wales, including SE Anglesey. Modis TERRA image at 1115 GMT on 1 March 2004. Snow SE Anglesey and North Wales. TERRA AQUA image at 1300 GMT on 1 March 2004.  Satellite images showing extent of snow cover in Wales between 27 February and 1 March 2004



    Snow was all but absent the first days of the month, but freezing temperatures returned on the 4th with precipitation falling as snow to lie above 1800 ft in the afternoon. Still lying on the morning of the 5th it soon thawed leaving only remnants above 3000 ft by the 7th, despite occasional wintry showers on some summits. Early on the 8th there was a light covering of fresh snow across most summits above 3000 ft but it soon melted. On the 12th there were small patches remaining on the flat top of Carnedd Llewelyn, but little elsewhere. With the weather turning colder again there were wintry showers on the summits on the 17th and wet snow fell and was lying down to 2000 ft at noon on the 18th. On the 19th there was snow lying thinly at 2800 ft generally and down to 2500 ft around Snowdon with recent fresh snow fallen. There was still some snow at 2600 ft on the 20th before warm southerly air melted most of it by the end of the day. The mountains were clear of snow to the end of the month.


    The last substantial snow on the mountains in May was in 1995 when there was snow on most summits until the middle of the month. To see any snow this year seemed unlikely, considering the warmth, until the 4th when it turned cold enough for ice precipitation above 2500 ft. Snow was likely to have been on some summits on the 5th, but low cloud prevented observation. On the afternoon of the 6th, when the cloud cleared, snow seen at 3100 ft on Carnedd Llewelyn and 2900 ft around Snowdon. No further snow was seen.

    Snowline will be back next season.

    Snowdonia snowline current histogram.

    You can view the snowline histograms for previous years here:

    Winter 2002-2003. Winter 2002-2003
    Winter 2001-2002. Winter 2001-2002
    Winter 2000-2001. Winter 2000-2001

    You can view complete snowline reports for previous years here:

    Winter 2002-2003. Winter 2002-2003
    Winter 2001-2002. Winter 2001-2002


    Observations are made as near to 0900 GMT as possible. I have a good view from Llansadwrn, weather permitting, across the Menai Strait, towards the Snowdonia Mountains. I can see the northern slopes of the mountain range from Moel Eilio (west of Snowdon), Snowdon summits (Yr Wyddfa and Crib Goch), the Carneddau and to Foel-fras and Drum on the eastern end near the Conwy Valley. With the aid of binoculars I make records of the lowest altitude of snow lying (>50% cover) and any patchy cover (<50%). The diagram is updated at least weekly, usually on Monday and Thursday during the season. Daily reports can be found in my weather diary.

    These pages are designed and written by Donald Perkins, copyright © 2003 - 2004

    Document dated 12 August 2003

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