Part 135.213a states:Wait what?
Isn't legal per your GOM/FOM? As far as the FAR's are concerned FF is perfectly legal to obtain an IFR wx brief from. I'm guessing your FOM specifically lists company approved sources and FF isn't on that list....?
Whenever a person operating an aircraft under this part is required to use a weather report or forecast, that person shall use that of the U.S. National Weather Service, a source approved by the U.S. National Weather Service, or a source approved by the Administrator. However, for operations under VFR, the pilot in command may, if such a report is not available, use weather information based on that pilot's own observations or on those of other persons competent to supply appropriate observations.
This has been interpreted as either ADDS or 1800WXBRIEF (or DUATS, previously), or utilizing FSS. FF is a hybrid weather source, so not technically legal. HEMS Tool is also a hybrid product, so not legal to launch on, but legal to decline with. So if filing/flying IFR, a valid brief is required, which means either FSS or WXBRIEF briefing.
You can still file through FF, which I do all the time, although I'm finding the IAF doesn't seem to be getting to Center when I go home, or they're just ignoring it, which is very possible.
ETA, this doesn't mean I don't use FF privately. Just speaking to Part 135 ops.