>>>I have a suspicion as to why no one ever mentions dispatchers, but I don't think you'll like it.
That's a given in my profession, but also a given since we see so few PICs grace our office for visits (unlike our required jumpseat rides each year, and folks, we're talking about the west side of the Pond here, FAA Part 121 ops).
JMHO, but NWS TAF accuracy has suffered here in recent years, and it's not only dispatchers who sometimes can miss the clues.
I had a call from the PIC of a PHX-MCI flight once, asking (in not an all that nice tone) why I as carrying OKC as alternate and 50 minutes of contingency. (How wasteful!) The rest of the conversation when something like this...
Why are your carrying all this fuel?
There are thunderstorms that are..
(Interrupting me) there are no thunderstorms forecast for MCI...
Well I know nothing's forecasted but there's a line up to the northwest that...
(Interrupting me again) and the convective sigmets have that line NW moving from 27030 so it'll be north of MCI...
Well, the convective sigmet may say 27030 but looping the radar indicates more like 33030 on the movement, straight for MCI.
Well, let's use TUL instead of OKC since it'll be closer and less fuel to get there...
I'm using OKC because the orientation of the line is such that if the line grows to the SW (as they commonly do here), TUL has an excellent chance at being impacted at the same time as MCI, and OKC would be further west and behind all that. (OMA WX sucked, in case anyone was wondering, and STL was on the other side of the probable line that would be forming.)
He then wanted to talk to a Chief Pilot about my reducing the fuel, and while I said that I'd be happy to 3-way the CP in, I was telling him up front that I wasn't going to be coming off the OKC and :50. He went with it, and wasn't "happy" about it.
Enroute and abeam AMA, the NWS snaps to the 33030 movement of the line and thoughtfully amends MCI's TAF for TEMPO 1/4SM TSRA (GR too!). I pass the info along, and suggest that he pull it back to LRC since other aircraft were just starting to hold at ICT. He ended up only holding at ICT for :20 (TUL got clobbered too, as expected) and he had a clear shot from ICT to OKC the entire while.
I'm by no means saying that it happens one way as often as it does the other, but the point is that it can, and that it takes communication between PIC and dispatcher to come up with an optimum plan. One party, be it PIC or dispatcher, assuming that they have all the info to the exclusion of all other players, can be in for a nasty surprise, and one that would have very likely been avoidable.
Again, that's all west-Pond dispatcher/PIC stuff under Part 121--your country's regs may well vary...