The forecast challenge has begun as I have figures I am going to throw at next week. They are, London pushes 23C on Wednesday but as the warmth spreads across southern Britain, the cold regroups across north of the UK and will dive south late week. It’s pretty much a case of going from a positive to negative NAO within 3-4 days.

As posted late last night, the ECMWF is now going to my idea that the ridge should be stronger with warmer 850 temps mid next week with the help of warm air crossing the Atlantic under the nose of a strong jet stream. As you know, my thinking is that warmth pushing off North America gets pulled up by the jet, speeding it up and driving this across the Atlantic only to enhance sinking, boost heights and strengthen pressure within a developing ridge which will extend north from Iberia.

Here’s the ECMWF 500mb and 850mb temps for next Wed.

Wed 500mb

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Wed 850mb temps

Right now, while the warmth looks likely in the South of the UK, it’s in Northern Ireland and Scotland which looks to remain much cooler and unsettled but it wouldn’t surprise me if we see more northward progression of the Iberian ridge, allowing Scotland to get in on some warmth too, but even if we don’t, I believe southern England and Wales should see this brief warm surge before the other shoe drops yet again.

Between Wednesday’s potential warmth and the cold return, ridging slides east and allows a sharp frontal system boundary to swing across the UK and with a high pushing off Canada and heading northeast towards Greenland, this will force very cold air positioned well north of the UK to relocate further south and within reaching distance of low pressure off the NE Scotland by Friday. This setup will allow unusually cold air to sink south over the UK AGAIN by next Friday into the weekend.

London may go from low 20s Wednesday to a struggle to make 10C on Saturday. As for Scotland, Northern Ireland and northern England, highs may be back in 5-8C territory with hill snow. Some areas within the Highlands could get another covering of snow with highs stuck at 2-4C. Clear skies and light winds by night will widely allow temps to sink to between 0/-2C in towns to -4/-6C in rural areas.

Here’s the 500mb and 850 temps for next Saturday

Sat 500mb

Sat 850mb temps

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Tags: april cold spell, april uk cold, april uk forecast, uk cold