Monday 13th April
Sunday once again brought a rash of showers crossing the area although the most intense downpours passed to the north and south of Marlborough, especially the last shower just before 22.00. Even so, a total of 5.8mm of precipitation was recorded making it the wettest day of April so far. Due to the build up of shower cloud and a brisk southerly breeze gusting to 22mph, temperatures were depressed with a maximum of 12.4C at 12.25 before the cloud increased, which was 1.8C below average. The clear sky overnight and still conditions, no breeze after 23.00, meant a cold night that saw the thermometer drop away to a minimum of -0.6C at 06.18. In fact the temperature dropped to freezing (-0.1) at 05.22 and back above (0C) at 06.18.
Monday revealed that thick fog had formed in the early hours limiting visibility to 200m at sunrise. The air and ground was very moist from the rainfall, which resulted in fog forming due to the air becoming saturated with the moisture, condensing as the temperature dropped. By 07.00 the sun had got to work and resulted in the visibility improving markedly that had cleared by 07.30. The unstable air will likely produce shower activity again today. As the ground and air warm up the air becomes lighter and rises where at a greater height it is cooler, at this point the moisture in the air condenses and showers arrive, that fade away late afternoon as the temperature drops, as on recent days. With the sky being clear for the first part of the night, another close to freezing early morning is likely on Tuesday.
There is a guide to planting that seeds are not likely to germinate until the soil temperature at a depth of 5cm is consistently at 10C or above. This month has only produced one morning at 08.00, the likely lowest point in the twenty-four hours, when that occurred, which was the 11th. The days ahead, from Tuesday onwards, are likely to bring that crossing point as both maxima and minima are likely to be just above the average whilst when we have sunshine, it is growing in strength. The peak solar radiation on Sunday was the highest this month with 953W/m2 at 13.15.
The week ahead will bring us a pattern of unsettled weather with predominantly sunshine and showers in the moist air stream from a southwest quadrant. The forecast surface charts indicate a series of low pressure systems arriving from the Atlantic, pushed on from the west by an active jet steam. Just to the east, high pressure over Scandinavia and to the southwest around the Azores, will resist the forward movement of depressions across the country, however, they will still send weather fronts across the UK with two warm fronts crossing on Tuesday and a cold front likely to arrive on Wednesday, producing the unsettled conditions.