Well I’ve addressed the big pattern flip that’s coming but today I want to look at just how chilly it could get with this setup.

First of all, check this out….

This often happens in solar downturn years not in winter but spring and often marks the big shift to a longer term cooler and wetter pattern. This shift could be significant to the longer term pattern!

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In order to get the above, you need a nice strong blocking high up over Greenland and the high currently dominating UK skies will retrograde WNW to a Greenland/Davis Straits position this weekend. Now with a low developing and positioning to the east over the North Sea, well this opens us up to the arctic. It’s very easy to start shouting the ‘S’ word again but one crucial aspect must be considered. TIME OF YEAR!

Based on the charts and setup along with abnormally low thicknesses for late April, daytime maximums could be supressed at just 4-8C across the Northern UK while in the South it’s 9-12C. Nights will certainly be cold but wind and cloud would likely keep overnight minimums slightly above freezing.

Check out the different in 500mb heights below now and Monday off the GFS.

While the ECMWF is showing snow and cold, keep in mind that we have an August strength sun now and so I suspect LOW LEVEL SNOW is unlikely, it may mix with rain at best.

The latest ECMWF surface maps certainly are classic for snow here it’s very very tough when you get to late April. A few are jumping on this and I guess hyping this but like we’ve seen back during the winter, the ECMWF model is often overdone when it comes to snow. To support snow to low levels, you pretty much need 80-100% of the atmosphere above your head at or below freezing and during the day, at this time of year, well that’s near impossible. High ground snow is far more likely and not unusual.

This to me is definitely a high ground event including high level road routes. Any accumulation is relative and probably above 300 metres and I think the model sees this.

Here’s the GFS

No doubt, this will be a shock to the system, it’s going to far far colder than you’d expect for late April/early May but just a few years ago, I drove up to Braemar in early May where some high routes were closed due to snow but by the time I got up there late afternoon, there was hardly any snow left as it melted and that was high ground.

While some are shouting ‘heavy snow’ and to low levels, I would be cautious. History shows us that low level snow by the end of April can fall but is unlikely to stick. Maybe I’ll be eating my words this time next week…

As stated for some time, we’re about to enter a much cooler and wetter pattern.

GFS ensemble 5-day mean 500mb height anomalies

5-day mean 2m temps/anomalies

This shift is likely in response to the on going strat warming over the pole that we couldn’t get back during the winter.

This setup of strong surface heating (when sun’s out) and cold to very cold upper atmosphere means fast, frequent and often blustery ‘convective’ showers, much more typical of April. In this setup with upper troughs, expect heavy and frequent rain and hail showers.

Is this a shift which takes us to this for summer?

Cooler and wetter? with El Nino and warmer than normal waters in the Atlantic acting as a trigger?

See video for the discussion.

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