May 20, 2019, was expected to have this general pattern, but with a few minor differences. A significant trough was ejecting across the desert Southwest, allowing a surface low to rapidly deepen across southeastern Colorado. Robust moisture was expected to already be in place during the morning hours, while a strong low-level jet trekked across the warm sector, allowing for impressive low-level shear to occur throughout the event.
The main difference between this event and significant events of the past was the initiation mechanism. Although storms were expected to form along the dryline, the most intense supercells were forecasted to initiate across the open warm sector by midafternoon. The reasoning behind this was that horizontal convective rolls would gradually deepen into thunderstorms, given the large amounts of instability and apparent lack of a cap (Galarneau at al. 2026). Since the forcing would be subtle and the storms would be in an environment with extreme low-level shear and large amounts of instability, multiple long-tracked violent tornadoes were expected.
