about a week or so before harvesting a white powder begins to appair on the leaves of the plant,anybody knows what that is? and is it a good sign? or a bad sign?
That sure sounds like powdery mildew, which is a fungus. The spores are around, and when the plant ripens the trichomes seem to give a good growing area for the fungus. It could affect or ruin your crop. This close to harvest you should cut off any sign of it, carefully, and continue growing. Or in your judgement, harvest early and manicure the plant immediately, removing all affected parts.
If you're indoors, which I imagine since it's spring there, you'll need to fix this for future crops.