21st April - 13th May
I am expecting temperatures to average about 0.5-1.0C above the 1981-2010 average in most parts of the country, with the period 21st-27th April coming out slightly cooler than average but the other periods coming out warmer than average.
Rainfall totals are likely to be above average in southern parts of England (by up to 40%) but most other parts of the country are expected to have below-average rainfall, with eastern Scotland likely to be driest of all (up to 50% less rain than usual).
Sunshine totals for the period will be slightly below average in eastern and southern parts of England, and near the east coast of Scotland, but elsewhere they are likely to be above average, with south-west Scotland and Northern Ireland likely to be sunniest relative to normal with excesses of about 20-25%.
Monday 21st April - Sunday 27th April
This week will be more unsettled, but there is some uncertainty over how unsettled it will be. The majority of the forecast signals and model outputs suggest shallow low pressure dominating over and to the west of the British Isles, but pressure will often be high over Scandinavia which may promote mostly dry conditions in the north and east of Scotland, albeit with frequent low cloud near to the North Sea coast. Slow-moving rain belts are likely to be an issue, especially in central and southern parts of Britain.
Mostly cloudy skies and showery rain are likely to spread north-eastwards through the country on the 21st (Easter Monday). These will clear north-eastwards on the 22nd leaving brighter conditions and some well-scattered showers, but more rain belts are likely to head in between the 23rd and 25th, most especially in Wales and central and southern parts of England. High pressure is likely to become more prominent near the end of the period, especially in the north, and so quieter weather is more likely on the 26th and 27th, with some sunshine in the north-west of the country but plenty of cloud in the east and south.
Most parts of the country will be wetter and cloudier than average during this period, with temperatures close to or slightly below normal. The north and east of Scotland, however, will be drier than normal and, in a reversal of the previous week’s situation, north-west Scotland is the most likely region to come out both drier and sunnier than average.
Monday 28th April - Sunday 4th May
The most likely scenario early in this period is a north-south split with high pressure ridging across northern parts of the British Isles and relatively low pressure at times in the south. This will result in mostly dry, sunny and warm weather in western parts of the British Isles, and a large majority of Scotland and Northern Ireland in particular, but most of eastern England will be cloudy and conditions may be wetter than average in the south and south-east of England. Late in the period, pressure is likely to fall from the west, resulting in more changeable weather, with some rain belts heading eastwards through the country at intervals.
This period, on the whole, is likely to be cloudier and slightly cooler than average in the south and east of England, and wetter than average in the south, but elsewhere, most places will be warmer, drier and sunnier than average.
Monday 5th May - Tuesday 13th May
There is considerable uncertainty at this range, but the most probable scenario is that low pressure will be in charge of the country’s weather early in the period, but with high pressure ridging north-east from the Azores as we head through the second week of May. Thus, the changeable regime is likely to continue until around the 10th, with fronts moving eastwards through the country at intervals bringing rain belts, interspersed with some brighter, showery conditions, but then the weather is likely to turn quieter after the 10th, with western and southern parts of the country most favoured for some warm sunshine. In general, sunshine and rainfall totals will not deviate far from their respective long-term normals during this period, while temperatures are likely to be slightly above average overall.