Forecasts rhymes with:
castes, casts, blasts, castes, casts, fasts, lambastes, last's, lasts, masts, nast's, pasts
Forecasts sounds like:
fabricates, first's, firsts, foreshadows, forest's, forests, forgets, forsythias, fractious, freightways, frigate's, frigates, frosts, fructose