Flash Flood Warning issued September 15 at 6:49PM CDT until September 15 at 8:30PM CDT by NWS Lubbock TX

The warning came from Doppler radar and automated rain gauges picking up thunderstorms dumping heavy rain across the area. Forecasters said flash flooding was already happening at the time of the alert, with another inch possible on top of what had already fallen. That kind of rainfall rate turns underpasses and low-lying streets into standing water fast, especially anywhere drainage already struggles to keep up.

Small creeks, streams, highways and city streets topped the list of risk areas, the Weather Service said.

For anyone out Monday evening, that means checking a route before driving through a low spot instead of after. Water can rise over roads quicker than it looks, and an underpass that seems fine one minute can fill in the next.

Three inches of rain in under two hours is enough to turn a normal Monday commute into a stalled car on the evening news.