  We characterize the kinematic and magnetic properties of HI filaments located
in a high Galactic latitude region ($165^\circ < \alpha < 195^\circ$ and
$12^\circ < \delta < 24^\circ$). We extract three-dimensional filamentary
structures using \texttt{fil3d} from the Galactic Arecibo L-Band Feed Array HI
(GALFA-HI) survey 21-cm emission data. Our algorithm identifies coherent
emission structures in neighboring velocity channels. Based on the mean
velocity, we identify a population of local and intermediate velocity cloud
(IVC) filaments. We find the orientations of the local (but not the IVC) HI
filaments are aligned with the magnetic field orientations inferred from Planck
353 GHz polarized dust emission. We analyze position-velocity diagrams of the
velocity-coherent filaments, and find that only 15 percent of filaments
demonstrate significant major-axis velocity gradients with a median magnitude
of 0.5 km s$^{-1}$ pc$^{-1}$, assuming a fiducial filament distance of 100 pc.
We conclude that the typical diffuse HI filament does not exhibit a simple
velocity gradient. The reported filament properties constrain future
theoretical models of filament formation.
