sometimes there is another option ...
plan a route that avoids the area of severe weather, (severe TS walls over the Alps is a reasonably frequent example).
not always possible, but when it is, take the safest option and explain your extra fuel requirement and routing to ops, if not be prepared to sit it out until more information is available: don't get airborne and "hope" for the best.
Have seen lemming like behaviour on STAR's resulting in several lightning strikes to several planes within a few minutes , end result : several AOG pending engineering attention, when all they had to do was to request a routing to another STAR entry point.
If it is there, and you know it is there, try and deal with the problem at the planning/ briefing stage.