You get to determine how often WXSIM (and WXSIMATE) run on your system. I run both at 2 hr intervals, so I don't see that mismatch.
The NWS seems to update forecasts at 6 hour intervals with the first in the morning being 'Today', then 'This Afternoon', then 'Tonight', then 'Overnight' .. the times for the change seem to happen about :15 minutes after the appointed hour (which I don't have the exact hours of change).
So.. my suggestion is to run WXSIM more often (like every 2 hours).