Welsh's conjecture on real flow roots

Let $G$ be a bridgeless graph, and let $\Phi_G(Q)$ denote its flow polynomial. Welsh's conjecture. For any bridgeless graph $G$,

$$\Phi_G(Q)>0\qquad\text{for }Q\in(4,\infty).$$

The conjecture parallels the Birkhoff–Lewis result for chromatic roots, but the source reports an explicit counterexample, the generalized Petersen graph $G(16,6)$, whose flow polynomial has real roots near $4.0252205$ and $4.2331455$.