Jeskai Ephemerate leans heavily on blue value engines like Murmuring Mystic, Mulldrifter, and Counterspell, so Red Elemental Blast both counters their key blue spells and can destroy a problematic blue permanent such as Murmuring Mystic before it snowballs into a wall of Bird tokens. Their Skred scales with snow permanents and can threaten our bigger creatures, but we out-size them with Bramble Wurm and Writhing Chrysalis regardless. Cutting lifegain for proactive blue disruption is the correct trade since this matchup is more about card advantage than racing damage.