Sunday, 24 May 2015

Weather guide Spring Bank Holiday Monday to Sunday 31st May 2015

Headline: Mostly dry with some sun to midweek, turning cool and unsettled with rain or showers

Last week's highlights

Wet last Sunday night and Monday morning, many parts of Wales had 20mm or more (wettest 30mm at Capel Curig) while parts of the Midlands received over 10mm (Hereford 14mm). Squally winds caused some structural damage and brought trees down in the Swansea area on Monday morning. Cool for much of last week especially on Wednesday when all locations failed to reach 14c, parts of WW coolest with max just 8.1c Capel Curig (persistent showers) and 10.4c Trawsgoed (only a few showers) and with a cold wind. Showery then on Wednesday with hail and thunder in places, parts of the Midlands, such as Coventry, caught a succession of hail showers through the day. Some coasts missed most the showers and had decent sunny spells, as at Milford Haven which had no measurable rain on Tuesday. Ground frost formed over the Welsh Marches and Vale of Evesham on Tuesday night as the showers died out, localised grass frost for some other parts of the Midlands as well.

Only a few showers on Wednesday, most of WW dry and bright, but still on the cool side everwhere but with the NW winds lessening. Another ground frost in places Wednesday night, lowest air temperatures Pembrey Sands and Llanwnnen min +1.7c. Thursday mostly dry and warmer with sunny periods, much of the Midlands above 18c, warmest Pershore and Coventry on 19.4c. Unfortunately with the wind off a still quite cold sea most of WW still pretty cool, decidedly so at Aberdaron near the tip of the Lleyn Peninsular max 12.3c, though Llanwnnen inland enough to attain the late May average at 16.4c. Some warm sunny intervals developed during Friday, although with light showers in places, max 20.4c Pershore and Hereford, 20.3c Llanwnnen, however most of WW did not better 18c and some coasts struggled yet again with onshore breezes and low cloud, Mumbles, Swansea at only max 13.0c the cool spot.

Contrasting fortunes Saturday, with WW away from Anglesey and Snowdonia having a rather warm sunny day, while most of the Midlands was rather cloudy with just a few sunny intervals, an exception being Herefordshire which was quite sunny and warm. Max temperatures Tirabad, Powys 19.8c, Hereford 18.9c, Pembrey Sands 18.5c,with Aberporth 13.4c coolest inspite of the sunshine, followed by Valley 15c, while the cloudier parts of the Midlands such as Coventry were around 16c. Coventry yet to break the 20c barrier this year which could end up the latest 'first 20c date' in the city's history, with June 1st 1983 to beat (please see the excellent )!

The week ahead

Plenty of dry if rather cloudy weather to the middle of the week, though some sunny spells, but then it turns cooler and unsettled quite appropriately to see out this rather cool and unsettled May! Sunday seeing a lot of cloud with a little rain or drizzle in places as as weakening front slowly crosses the country. Most of this dying out/ clears afternoon with some late sunny intervals for WW and the NW Midlands in particular, maxima Sunday 14c WW and 16c Midlands. Dry with clear intervals tonight. Bank Holiday Monday will be mostly dry, a light shower cannot be ruled out entirely however, with sunny intervals developing, but highs quite cool at between 13 and 17c.  Dry overnight too bar the odd spot of drizzle for WW.

The omnipresent Atlantic high to our WSW attempts to exert a ridge over the UK once more during Tuesday and Wednesday which will be largely dry as a result. Troublesome weak fronts keep tracking SE though in the NW flow bringing areas of cloud if little in the way of rain at all. Tuesday then and one such frontal sytem means a lot of cloud with spits of drizzle in places, hopeful though that sunny intervals develop afternoon. Maxima Tuesday generally 15 to 18c, but 20c is just about possible where better sunny spells occur, fairly light breezes from the NW. Clear spells and calming air during Tuesday night could lead to a grass frost in places. The ridge declines during Wednesday but still a mostly dry and bright day, highs again in the 15 to 20c bracket dependent on cloud/ sea breeze, etc. Rain fronts could well arrive into Wales during the evening with quite a wet night everywhere.

A low passes close to Scotland during Thursday which sees early rain clearing to sunny intervals and showers, some heavy with hail and thunder possible. Cool and windy too for Thursday, gale force NW gusts in places and poor maxima of  12 to 15c (worst over a very showery Snowdonia).  An unsettled mobile pattern likely come the end of the week, so although a transient ridge dries things out Thursday night into Friday, even with some sunshine for a time,  further rain fronts (perhaps even a small low system) look set to cross Wales and England eventually during the day, although perhaps not until late on.  Next weekend too continues in a similarly unsettled vein, bouts of rain and strong winds coming through, with drier brighter intervals between, and generally on the cool side. Let's see what Summer will bring?

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