Well, I just about have a handle on the expected weather for the Jubilee Bank Holiday weekend. Do you feel lucky?

Thanks to Paul for the photograph…again.

Showers will continue this evening and the first part of the night – some heavy ones around. Drier later with limited clear spells, down to around 9’C.

Tuesday will see widespread heavy showers. Unlikely to stay dry, most places getting at least a few heavy/very heavy showers – hail and/or thunder possibly mixed in. Some sunny spells, though fairly limited, especially in the morning. Around 15’C. Some clear spells overnight, some cloud – especially later. Down to around 7’C.

Wednesday will see plenty more showers, some will be heavy with a small chance of thunder. Some sunshine at times and a small chance that you’ll miss the showers – though more likely you’ll get a few. Temperatures up a tad to 17’C. Mostly clear skies overnight, down to around 6’C.

So, the bank holiday weekend. For a few weeks I thought the more likely outcome would be a fine or more fine weekend, with some warm sunshine at times.

However, last week, the weather models were suggesting a fairly good chance of low pressure moving up from the west of Portugal/Spain, bringing at least some heavy showers for some of the long weekend.

Over the weekend that risk had reduced, and high pressure looked set to build in from the west from Thursday onwards – alas, the risk has once more increase of that low pressure making it close to the south of England, so though there is a huge amount of uncertainty for Saturday and Sunday with the potential for some heavy rain and/or showers.

I’ll attempt some details, but remember that details are uncertain, and become more so every day.

So for Thursday, the general picture is low pressure to the west of Portugal/Spain, with another one over Scandinavia – with high pressure trying to build over the UK.

It will be dry and it will start sunny. Some uncertainty on cloud amounts, it may stay mostly sunny but more likely quite a lot of cloud will bubble up from mid/late morning onwards, with more cloud than sunshine – but pleasant enough. Reaching around 20’C – should the less likely sunnier outcome occur, then maybe 22’C. Fairly clear overnight though some cloud, down to around 11’C.

Friday sees the low pressure edge a bit closer, so there will be a risk of a shower, but also warmer air will be dragged up too. Probably fairly sunny, some cloud but more sunshine than cloud overall, and temperatures somewhere in the range of 21’C to 24’C. A 20% chance of a heavy, possibly thundery shower later in the day, or into the evening. That smallish risk of a shower still there overnight.

By Saturday things are very uncertain – and depend on the position and development of the low pressure system trying to move up from Spain. I’d say the slightly more likely outcome is a fair day with some sunny spells and a small chance of a shower – likely less warm than Friday. However the slightly less likely outcome is that rain spreads up from the south, rather overcast and cool, possibly heavy and thundery rain/showers mixed in. Talking a roughly 60/40 split in terms of chances.

Sunday is similarly uncertain, with a similar split of 60/40 in terms of fine and warmish or wet and cool. Somewhat more likely to be the opposite of what Saturday was, but it could be the same.

Certainly possible that both days could be wet, or both days stay fine. Around a 30% chance that both Saturday and Sunday are fine, 20% chance that both are wet, 50% chance that one day is wet, one day is fine. Very rough percentages!

So, the uncertainty probably isn’t what you hoped for, but it is where we are. I can easily imagine Saturday/Sunday still being uncertain when I do my next forecast on Thursday – it is fine margins in terms of how that low pressure near Portugal/Spain behaves.

Suggestions for early next week is that an Atlantic low pressure system moves across either Monday or Tuesday, bringing some rain, followed by showers, but possibly followed by something drier and warmer later in the week.