18th June 2017
Festival Run Up
High Pressure building over the UK this weekend, this lasting into next week, and only slowly weakening before Wednesday, so a settled and dry run-up to the festival seemingly likely. However there is a slight risk of a thunderstorm on the Tuesday, but the likelihood is that they will stay further East over Eastern England.
This chart shows today’s 12Hz GFS run, with the projected rainfall and CAPE values (potential energy in this case for thundery activity.
After the gates open
A slight change in the pattern with the pattern brought forward around 12 hours from yesterday with the cold front previously forecast Early Thursday, now forecast Wednesday afternoon, with the High Pressure moving away quicker than suggested.
Wednesday 21st June – High Pressure is forecast to be centred to the East of the UK, and slightly further East than suggested yesterday. Winds are likely to be from the South, with a front edging in from the West later in the day, with some patchy rain for Glastonbury possible, but probably not amounting to that much. A very warm day is still expected with temps around 26c with some sunshine around the front. Some uncertainty as to the timing of the front now expected.
Thursday 22nd June – A westerly flow is now favoured with Low Pressure to the North and High pressure to the South, the pressure gradient is expected to be slack with light Westerly winds expected. It is now expected to be dry on the Thursday, on the proviso that the cold front moves across South Western areas some time on the Wednesday. A bright day with some sunshine is expected with temps 22-25c, so cooler than forecast yesterday.
Friday 23rd June – The westerly theme is set to continue, with lower pressure to the North of the UK and higher pressure to the South of the UK. At this stage, Friday looks like being a dry and bright day for Southern parts of the UK. There are some fronts over the UK but current timings suggest these will be over Northern parts of the UK for Friday. Temps are set to be in the range 19-21c and sunshine amounts are variable but probably on the low side.
Saturday 24th June and Sunday 25th June – The weather patterns sees High Pressure to the South west and Low Pressure to the North East, with North Westerly winds for South Western parts of the UK. This is likely to give a mix of sunshine and showers, but hopefully for the sheltered South Western areas, the showers will be scattered. Temps into the high teens on the Saturday, perhaps low 20s on the Sunday.
Two of the 4 GFS runs have total rainfall 2-5mm the other two 5-15mm, in both cases, the heaviest of the rain is forecast from Thundery showers on Tuesday afternoon.
What could go wrong
The Thunderstorms on Tuesday are potentially troublesome, currently it should remain mostly dry, but if there is a direct hit on Glastonbury, this could massively change ground conditions.
Also some of the fronts edging Eastwards over subsequent days may prove to be wetter than currently suggested.
Providing the thunderstorms on Tuesday miss Glastonbury, it looks a very warm day on the Wednesday, with only patchy rain expected when the cold front from passes through sometime Wednesday.
Thereafter a Westerly flow is set up but looking dry but cooler for Thursday and Friday, while the weekend may see some sunshine and showers.
So while the conditions are now not expected as yesterday, it is still probably looking pretty decent and mostly dry over the Glastonbury extended weekend.
Mud bath 0 Dustbowl 10
7 out of 10 throughout, while some rain is possible at times, it should not cause too many problems.
But it is Glastonbury so always take your wellies, but this year take your sun cream as well.