Messi's contribution was a wonderful hat-trick - the third goal an impudent chip from the edge of the area.
Carles Puyol also got on the scoresheet with home defender Ezequiel Luna adding a late fifth with an unfortunate prod past his own goalkeeper.
Real Madrid beat Real Mallorca 2-0 to remian in second place.
Madrid had greater difficulty with the snow in the capital than they did with a toothless Mallorca side.
But despite the wintry conditions, Manuel Pellegrini's men strolled to victory with goals from Gonzalo Higuain - a sublime 25-yard curling effort - and Esteban Granero.
Valencia had a comfortable 3-1 win at Xerez to strengthen their hold on third position.
Xerez, who have now accumulated just seven points from 17 games, threatened a surprise when Carlos Calvo cancelled out Juan Mata's opener.
But Valencia upped their game to outplay their valiant, if limited, opponents. David Silva restored their lead and a fine solo effort from Carlos Marchena settled matters.
CLUB Pl W D L GD Pts Barcelona 17 13-4-0 +32 43 Real Madrid 17 13-2-2 +29 41 Valencia 17 10-5-2 +14 35 Deportivo 17 9-4-4 +4 31 Sevilla 17 9-3-5 +11 30 Mallorca 17 9-3-5 +10 30