Thundery wintry showers

nother warm dry March for most
With high pressure remaining dominant to the south of Britain it looks set to be another mild dry March except for western and northern Scotland.

However before the mild dry weather returns there will be a cloudy wet blip over the weekend of the 3rd/4th March. An Atlantic weather system will bring rain eastwards on the 3rd followed by brighter showery weather, the brighter weather not reaching East Anglia and the southeast until evening. A southerly tracking depression will then bring a cold, wet and windy day across England and Wales and southern Scotland on the 4th, with temperatures suppressed at 4 to 7C for most and gales in some coastal areas. There will also be snow on high ground across southern Scotland and Wales, with some sleet possible to low levels. As cold air digs in behind from the north, wet snow may occur more widely to low levels across southern England overnight 4th/5th.

After the cold wet episode high pressure will again establish to the south of Britain bringing mild westerlies, but eastern parts of England (especially East Anglia) are likely to have another cold wet day on the 5th, while other areas become dry and sunny, with a slight frost early in the day. During the 6th the dry sunny weather will transfer to southern areas while western and northern Scotland will become cloudy and wet, and it will turn milder. The 7th will see the rain belt spread south-eastwards across the country (though with only small rainfall amounts in the south) and brighter weather with wintry showers across the northern half of Scotland.

High pressure will be persistent to the south during the second week of March, bringing dry and generally sunny weather to most of England and south Wales, but in north Wales, north-west England and most of Scotland and Northern Ireland it is likely to be cloudy with rain at times. Eastern Scotland will most likely be dry but often cloudy. Temperatures will be consistently above the seasonal average, but never exceptionally so, reaching 10 to 13C by day across most regions. Frosts will be rare, though some central and southern parts of England may see slight frosts under clear skies.

The signals for mid to late March suggest high pressure extending further north. An interlude of chilly northerly and north-westerly winds is likely in the third week as part of the transition, with some short-lived snowfalls possible across Scotland and northern parts of England plus northern Ireland and north Wales, but in the south temperatures probably won't fall far below normal. The last third of March will probably be dry and settled with warm days and near-average temperatures by night as high pressure settles close to the British Isles.

Overview
March 2012 will be quite a mild March, I am predicting a Central England Temperature of 7.3C. Mean temperatures will be 0.5-1.0C above the 1981-2010 average in most regions, though note that they will be more like 1.5C above most earlier reference periods.

Despite a wet interlude on the 3rd-5th, March is unlikely to alleviate the water shortages in southern and eastern England. Rainfall will be close to average in western and northern Scotland but elsewhere shortages of 30 to 60% are expected, with the largest shortages occurring in south-east Scotland and south-west England.

Sunshine totals will be above normal in most regions for the sixth consecutive March. Slight shortages are expected across Northern Ireland and western Scotland (about 10 to 20% below average) but excesses of 10 to 30% will occur in most central and eastern parts of England and also in south-east Scotland.

Forecast issued by Ian Simpson (aka TWS) on the 3rd March 2012.

A large anticyclone over Russia has narrowly failed to bring exceptionally cold air across from the east, but nonetheless the UK lies on its periphery and is experiencing notably low temperatures.

During the 3rd and 4th Atlantic weather systems are set to push in from the west, and as these collide with the cold continental air we can expect some snowfalls. The 4th will see a band of rain, sleet and snow move across from the west, mostly falling as sleet or rain in Ireland, south and west Wales and south-west England, but falling widely as snow across the rest of England. There is still considerable uncertainty over where the snowiest areas will be. The cold air will hang on in south-eastern areas during the 5th-7th with the snow petering out. Further north and west the snow will be followed by sleet/rain on the western flank of the band, potentially leading to slushy and, subsequently, icy conditions. Some rain belts will also affect Ireland and northern and western Scotland from time to time.

It will remain mostly dry during the second week of February and start off dry, sunny and cold for most, especially cold towards the south-east. I expect milder air to push down from the north-west towards midmonth as the Russian high slowly declines and sinks south-eastwards, and our ridge of high pressure sinks south-westwards towards the Azores. This will bring cloudier conditions but with high pressure close by it will still be mostly dry, with the mildest temperatures likely to be located across eastern Scotland.

There are strong signals for a build of pressure over Greenland as we head towards late February. Therefore, I expect a couple of northerly outbreaks to occur, probably one shortly after midmonth and one during the last week, the latter being the more potent. Because pressure is likely to be persistently high to the north-west, we aren't talking those tame short-lived northerlies either- snowfall should be widespread, especially in northern and eastern districts, and a north-easterly type is possible towards the end of the month. However, it will not be as cold in south-eastern areas as during the first week of the month.

February 2012 will be quite a cold month, in contrast to January, though probably not exceptionally so. My prediction for the Central England Temperature is 3.5C, but it could well end up colder than that. Negative temperature anomalies, relative to the 1981-2010 reference period, will range from 0.5C in northern and eastern Scotland to about 2C in south-east England.

It will be a dry month almost everywhere. Precipitation will be close to average in northern and eastern parts of Scotland but will be 30-50% below average in most other regions, and over 50% below in parts of western and south-western England and much of Wales.

Scotland and Northern Ireland will have quite a cloudy February with sunshine shortages of 10-30%, but it will be a sunny month over much of England and Wales, sunniest in the south-west with excesses of 50% likely in Cornwall and Devon, with excesses of 10-30% in most other regions.