In reply to barnesy1977:
Here are three possible options:
1) You play safe and wait for a better day / forecast
Absolutely valid to play safe
2) You go ahead with your walk regardless
In my opinion a less safe option but you might get lucky
3) You go ahead with a walk but make a judgement according to the weather and conditions you meet on the day.
This may mean planning and doing an easily navigable lower level walk if the weather / conditions are not good for Snowdon / your party. Or it could mean going ahead with the Llanberis Path route but making a judgement as you go ( depending on weather / conditions / condition of the party members ) as to whether / when you should turn around and retrace your steps.
The weather does not always match the forecast; it may be better, worse or the timing may be different. I also notice the forecast at the moment is to improve as the morning goes on and that the snow is only forecast at a very high level on the mountain. It may not snow, snow may be little and wet and may melt fast.
This third option will help you gain knowledge and experience, but does come with the proviso that you have the equipment required as Ruth pointed out such as waterproof jacket, trousers a map and possibly compass with the knowledge and skills of how to use them.