This evening's model runs have certainly thrown a spanner in the works for forecasters and certainty.
The GFS 06z was pointing more towards a hot scenario with high pressure gradually going from the west to east which would eventually bring in a southerly to southeasterly flow of air off Europe.
GFS 12z has come back to the scenario of its 0z run in that after a hot or warm weekend with the jet stream close by to the north of the UK and Ireland, the westerlies return but low pressure is still way to the north so not even of much influence. This is a clear example of a weak jet stream, the GFS being too progressive and its westerly bias is evident. When you look at the first chart below, you would think that the high pressure to the south would fully ridge up to us or push to the east like the 06z run showed. However, the 12z doesn't do this at all.
ECM 12z goes the high pressure route though at +192 hrs, it goes a bit "wonky" in weakening the high pressure along with looking like cool 850hPa temperatures coming down from the northwest but at the end, there is a thundery trough just to the southwest of Ireland with both countries in a hot plume of air.
UKMO 12z suggested a hot Sunday 22nd July.
CFSv2 suggests a hot end to July and start to August 2018 with plenty of further blocking areas of high pressure over us or to the east of us drawing in a warm southeasterly flow. Week 2 (23 to 29 July) is particularly hot on its latest run with temperature anomalies around 2-3c above average which for July is very hot indeed.
Different solutions are still being thrown around so none of this certain and is to be taken with a pinch of salt for now.