( Snow ( ( can ( form ( if ( there ( is ( ( enough ( water vapor ) ) ( in ( ( the air ) ( for ( clouds ( to develop ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Snow)) (VP (MD can) (VP (VB form) (SBAR (IN if) (S (NP (EX there)) (VP (VBZ is) (NP (NP (JJ enough) (NN water) (NN vapor)) (PP (IN in) (NP (NP (DT the) (NN air)) (PP (IN for) (NP (NNS clouds) (S (VP (TO to) (VP (VB develop)))))))))))))) (. .)))
Snow can form if there is enough water vapor in the air for clouds to develop.
(ROOT (S (NP (NNP Water) (NN vapor)) (VP (MD must) (VP (VB lose) (NP (NN heat) (NN energy)) (SBAR (IN before) (S (NP (NNS clouds)) (VP (MD can) (VP (VB form))))))) (. .)))
Water vapor must lose heat energy before clouds can form.