Results are reported from an improved measurement of $ u_mu rightarrow u_e$ transitions by the NOvA experiment. Using an exposure equivalent to $6.05times10^{20}$ protons-on-target 33 $ u_e$ candidates were observed with a background of $8.2pm0.8$ (syst.). Combined with the latest NOvA $ u_mu$ disappearance data and external constraints from reactor experiments on $sin^22theta_{13}$, the hypothesis of inverted mass hierarchy with $theta_{23}$ in the lower octant is disfavored at greater than $93%$ C.L. for all values of $delta_{CP}$.
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