Answering the system-agnostic tag I present you Empire Weather
The simple charts provide a glossary for seeding descriptions, accounting for prevailing weather, and an instant weather option as well. All using a single d10.
Belated Update... h/t @ryanfaescotland
Eight years and counting. I saw a recent upvote, and Ryan's comment. Yes I'm still using this chart. As recent as last week in my current D&D 5e in Greyhawk campaign (entering its almost fourth year!)
Dave Graffram simply makes it direct and with a dash of spice to make it setting relevant. IRL I had the opportunity to take a mountain hike that started off partly sunny. In the first 10 minutes of the hike, thunder. The guide said something witty about bear caves and trees being lightning rods. 30 minutes later, a thunderous downpour that lasted for the entire hike. Unprepared, the entire group was soaked to the skin. The trails became treacherous: roots and rock, covered in rain soaked bark and mosses, provided no perch for shoes. The hot day turned cool in the cloud cover and rain, then humid after the downpour.
I made a comment to my players in the following session about these experiences providing a frame for describing weather in the game, and justifying a liberal use of the Exhaustion rule in overload travel.
Empowering a prophecy without railroading, using mechanics, is very much possible. The "stick" is not so useful here as is luring the player with the "carrot". There are a number of more-or-less successful games that do this with great success*, to the point that some use it as a central part of character development, so there's evidence in the wild that this is possible.
Substantial bribes
All the games I've observed doing this effectively offer a significant "bribe" that tempts players to choose to act in line with their fate. Such a bribe must be large enough to give the player a true dilemma – do I act with freedom to choose the "best" course of action for my character, or do I take the big mechanical boost and do what the prophecy says I must?
The bribe has to be big, unbalancing almost, in order to make it large enough to be the equal to how much a player values their freedom of choice. The extra that they're getting must be valuable enough to really make them consider it. In D&D terms, a +5 or more to all skill and hit rolls for the duration of the time where they are facing the direct consequences of their choice (the resulting battle, the escape from the crypt, etc.) might be suitable. Another effective carrot is the game's improvement currency: a large XP bonus (perhaps 10%, or more, of what they need to level) can be very tempting for a player.
This can be tweaked as you go, to. You don't have to tell them at the outset that every such moment is worth 1000 XP — instead, when they come to a pivotal moment in their fate, you can mark it as such by saying "…and if you choose X against your better judgement, it's worth N experience." You can offer variable carrots tailored to the importance of the choice, too, so that you give bigger bribes to properly balance the sides of the dilemma.
Free choice
It must always be a free choice. You might set the dilemma, but a player hugely values their freedom to choose.
By putting the choice into your player's hands, you make it more likely that they will fulfill parts of the prophecy/curse/fate and you don't railroad it. As long as you're always prepared to accept the player's true choice (don't up the bribe after they refuse, for example), they will feel it really is their free choice, and you'll get much more buy-in for when they do choose to accept the prophecy.
Not everyone likes talking mechanics
The one caveat is that some players who go for deep immersion will really dislike baldly discussing mechanics when they're trying to choose according to their character. There's no real good way around this without seriously annoying the player and undermining their buy-in. The compromise application of this idea is to not tell them that they have the choice – but when they do choose the path of prophecy, narrate how their sword swings truer (as you start appling a hit bonus to their rolls) or how a great weight of foreboding settles in their chest (as you give them bonus XP as an aside). This will create the association between bonuses and accepting their fate, without interrupting their internal narration and breaking their suspension of disbelief.
* One example is The Riddle of Steel. When you're acting in line with your Fate during a pivotal moment in the prophecy, you get a very large bonus to all your rolls during the fallout of the choice. Another is Dungeon World, where you can get into situations where if you do a thing that you normally wouldn't choose, you get to mark XP.
Best Answer
Ask more generally about their comfort boundaries
Tell the party that you have some ideas you think might be crossing the line, and ask them where they'd like the line to be drawn. In that context you might even give examples and include something similar to your idea as just one of several.
Throw in a scaled-down version as a test
Use the general concept that you're concerned about as the inspiration for a minor encounter/adventure, scaled down and probably depersonalized (NPCs being the targets rather than the PC in question). Then watch their reactions.
This can have the added narrative benefit of foreshadowing and parallelism if you do go on with the main idea.
Ask a mutual friend
Present the scenario to someone who knows the player in question well but isn't involved in the game, and ask them for their opinion.
This is not an excellent option: the friend's guess might be wrong, and it's sneaky, so might not be appropriate for your group's trust dynamic.
Don't underestimate your players
I'm often surprised by how much better our games are when the players are clued in to what their characters have no idea about. It gives the players opportunities to consciously up the stakes and place their PCs in dramatically tense situations.
I liken it to the film style where the audience is shown something dangerous before the heroes know it exists, to increase the narrative tension without giving the heroes a chance to prepare for the danger.