The Weather Prediction Center first issued a Level 2 out of 4 flash flood advisory for Monday, but has now extended the threat into Tuesday. A flood watch is now in effect for Monday.

"Life-threatening flash flooding" is ongoing in Kerr and Gillespie Counties -- including the areas of Kerrville, Comfort, Ingram, Hunt, Mountain Home, Waltonia, Harper, Kerrville-Schreiner Park and Cypress Creek -- according to the National Weather Service.

Residents living south of the San Saba River in San Saba County have been ordered to evacuate due to river surging.

The National Weather Service warned that the Guadalupe River could surge to nearly 15 feet—5 feet above flood stage—by Sunday afternoon.

Scholars and designers of early warning systems say that there are still huge gaps in our ability to predict flash floods and warn those at risk.

The Flood Watch in effect for parts of the southern Plains, including much of Oklahoma and Texas, was expanded southeast this morning to encompass areas that were hit hard by catastrophic and deadly flash flooding last weekend, including Kerr, Travis and Burnet Counties.

Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

Heads up if you're in the Hill Country or know someone who is. The threat for flash flooding in the areas devastated by last Friday's flooding have increased.