Can I use Zephyr Strike outside of combat to increase my running speed?

Question

The spell Zephyr Strike, from XGE, has the following text:

You move like the wind. Until the spell ends, your movement doesn’t provoke opportunity attacks. Once before the spell ends, you can give yourself advantage on one weapon attack roll on your turn. That attack deals an extra 1d8 force damage on a hit. Whether you hit or miss, your walking speed increases by 30 feet until the end of that turn.

Clearly this spell was written with combat in mind. I'm curious what support, if any, exists for using it outside of combat for the purpose of increasing a character's movement speed, for instance in a foot chase.

What I would like to happen: I cast Zephyr Strike, waive the attack, and immediately trigger the bonus 30 feet of speed (say, to 60 ft). Since Zephyr Strike's casting time is a bonus action, I then take the dash action, doubling my speed to 120 feet. I have this speed for 6 seconds.

My interpretation of the spell as written: The bonus to speed requires the player to take the attack action. The extra speed only lasts until the end of the turn. So to gain the speed benefit, a player must attack something, which uses their action and prevents the use of the dash action while under the effect of the spell.

Obviously the DM can rule however they want, but I'm curious what support the rules might have for my preferred outcome.

Answer 1

No

The text is clear that you must make a weapon attack on your turn to get the bonus speed. The only ways of making a weapon attack on your turn use the Attack action or Cast a Spell action (using the right kind of spell). As such, you do not have your action available to Dash.

There are some niche ways of triggering an opportunity attack using your Reaction but I’m pretty sure you would need to Cast a Spell to cause them. Of course, we could come up with highly specific and unlikely scenarios that would work: like having a friendly Bard Ready Dissonant Whispers on a creature adjacent to you to trigger after you cast Zepher Strike, giving you an Opportunity Attack using your Reaction on your turn.

If you have more than one Action (e.g. Action Surge) or can Dash as a Bonus Action (e.g Cunning Action) and wait until a latter turn, then sure.

Answer 2

It is only 60ft. By the wording of the spell, attack is what triggers speed increase and is not optional, so you will be able to up your speed only to 60ft/turn (no spare action for dash). I think rogue can dash with bonus action, so 120ft is still an option, if you're ok with running for 180ft/2 turns instead of 120ft/1 turn. Even then, spending all those actions to dash would net you the same result, so why bother?

Ask your DM if they allow it Attack is a requirement to get speed increase, but I don't see why your character can't gain extra speed without spending action to attack thin air.