We are about to (assuming every simulation isn't just a pub run due to COVID) go into a very unusual cold spell. The week will start with high pressure and high diurnal temperature ranges with temps in the  mid teens by day and subzero by night. By the weekend, however, we will see a blast of cold air from the NE bringing colder uppers than we have seen all year.

For NErn areas this is not even marginal. Any showers will fall as snow and the snow will lie during the nights (although during the day expect sleet and slush). 

The cold snap lasts until at least Tuesday (although it may be more rain by then) with further extensive nightime frosts. And there is a possibility of a 2nd wave next week.

Finally high pressure watch is back! We broke the Wales record a few months back. This time we are likely to break the all time UK March record which is only 1044hpa (note the 1046 isobar).

The most interesting weather to watch from your house. Don't go out and enjoy it because you should be self isolating!

First cold snap showing partial thicknesses of about 127.5dm. To be sure of snow you need to be below about 129.5dm. Not even marginal. That's how cold it is on Sunday.

To be sure of snow we also need precipitation. Where is that coming from? It all looks very dry to me. Or is this setup conducive to streamers that are not showing on the models at this range?

Shower activity as the very cold air mass moves down over the North Sea: this shows convective cloud and precipitation at midday on Sunday.

Thanks. Fingers crossed.

* Pressure.

This is the kind of scenario you need to break an all time April maximun temperature record.

Heavy snow moving into a cold airmass.

Not forgetting the HP element of all this.

The March HP record is almost certain to fall (despite it occuring at the back end of the month)

In fact NI has an outside chance of getting to the all time record of 1051mb

The underrated aspect of all of this is the HP record.

A few months back there was a bit of uncertainty whether the record would fall (it did although only in Wales).

The record will fall this time (march all time).

AROME showing a few snow showers inland on Sunday morning.

The arome is really good when it comes to precip type, pretty poor though at getting shower activity right.

WRF 12z has pepped up the predicted shower activity a little. By Monday morning it's showing a slight covering over some eastern and central areas right down into Kent. Obviously areas with some elevation facing the NNE flow will do better as always, with rather more shower intensity and slightly lower temperatures.

Wow the HP is just insane. Records that could go.

Record / Threashold / Likelyhood

Highest March pressure ever / 1048.0 / Certain

First 1050hpa outside of Winter / 1050.0 / More than 50% Likely

NI all time record / 1051.0 / Probably around 30%

All time record / 1053.7 / Very unlikely

Could be if the lake effect is rather weak that the orogrophy over the pennines provides the lift needed to produce showers. You can get situations where the lake effect produces showers well inland and not at the coast because of this. Although when it happens the showers tend to be light although they also tend to merge into continuous precipitation.

We are literally hours (minutes?) away from breaking the all time march HP record.

Suprised this is getting no coverage!

And there we go.

Record fallen.

I have seen a report that pressure at Stornoway has reached 1048.2 mb. Has it now peaked or is there a possibility it may rise further?

Going to rise further. 1050+ is likely, and this will be the first time it has ever happened outside winter.

Aaaand. That record has now also fallen.

Some very beefy showers forming in southern North Sea which may affect the Kent coast around 9am.  Keep an eye out, may be the first (albeit very wet and sleety) snow Ive seen falling in 2 years.  Last time I can remember seeing snow falling IMBY was March 2018.  

In the NE the snow is quite dry and powdery. Should be easily cold enough for some wet snow in the SE. Those showers off the kent coast look incredibly beefy.

It's the same old thing down here, by the looks of it - the first band of showers is fizzling out as it approaches Kent. The second, heaver band looks a better prospect, but it's a long way out still.

Should any of the showers make it here, I'll let you know what they contain!

EDIT: And according to GFS, at least, it's -10C at 850 here... several degrees below the coldest recorded last winter and remarkably low for the time of year.

Light (a few flakes TBH) snow shower here a few minutes ago.

Reading 1048.1 mb here currently, while Malin Hd on the very north coast is reading 1050 mb, so the March record of 1047.1 mb recorded all the way back on the 13th back in 1900 is gone. All time highest reading in Ireland is 1051.9 mb, which I doubt will be broken this time around but there is a few hours of opportunity this morning before pressure starts to recede again in the afternoon. 

I will add, just for a bit of fun, that the end of March 1816 saw a strong high located in a similar position as the current one. Let's hope that we don't get to see a similar summer!