City officials say severe weather which passed through Thursday may be at least partially responsible for a large sink hole in West Allis.  A water main break in the afternoon led to the creation of the 20-foot hole.  West Allis officials say it will take at least a day for fix the problem.  The sink hole was reported at about 4:00 p-m and crews worked all evening, then returned this morning.  Bitterly cold weather, followed by a warm spell, alsoplayed a role.  No private property was damaged by the sink hole and no injuries were reported.