Once you get the hang of it, it is easy. To me there is 3 equations. First the percentage.

So if it says 40% chance of rain then what it means (1st equation) there is a 40 % chance of receiving 0.2 mm
of rain or more. 0.2 mm is the lowest BoM record.

Then the forecast may say 5 to 10 mms ( equations 2 &3)

Equation 2. 5mm. BoM are saying there is a 50% chance of receiving 5mm.
Equation 3. 10mm. Bom are stating that there is a 25% chance of receiving tham 10 mm of rain or even more.

So for tomorrow

.

That tell us there is a chance of a thunderstorm but if it eventuates it will be a dry storm or very little rain. Therefore with the wind there is a great risk of lightning causing bushfires.

For a full read of how to understand the forecast it is here.

http://www.bom.gov.au/NexGenFWS/rainfall-faq.shtml