XXX. May I ask how fast / slow you are going when this cloud 'comes upon you'?
Using a visibility requirement of 8km (approx 4 nm), you should be able to see that distance ahead, provided you are looking out the window. Even if you are travelling at 240kts, you would have at least 1 minute to realise that this cloud is approaching. That should be plenty of time for you to manv or liase with ATC to sort your clearance/tracking out.
If you are like most other VFR lighties and travelling at 100kts, then you will have even more time up your sleave.