Long-time precursors of order 5 times the global energy confinement time are observed for disrupting plasmas at the high-density limit on the Texas Experimental Tokamak. These precursors, occurring well in advance of any change in the plasma MHD activity, are reflected in the electron particle and heat transport along with the density fluctuation level. Enhanced microturbulence is proposed as the physical mechanism for the confinement degradation and subsequent disruption.