I think the problem for the forecasters is demonstrated by the Atlantic Pressure Chart:
Noon Saturday is T+60, and this shows an Occluded front right on our course across.
One side will be OK, the other cloudy and wet!
Met Office: Surface pressure forecast
Occluded front (or 'occlusion')
Occlusions form when the cold front of a depression catches up with the warm front, lifting the warm air between the fronts into a narrow wedge above the surface. Occluded fronts bring cloud and precipitation.
So, I guess we'll get what we get