We present results from a semicoherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the $mathcal{J}$-statistic, and by analysing data from Advanced LIGOs second observing run. In the frequency range searched, from $60$ to $650,mathrm{Hz}$, we find no evidence of gravitational radiation. At $194.6,mathrm{Hz}$, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of $h_0^{95%} = 3.47 times 10^{-25}$ when marginalising over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering.
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