FROM THE NATIONAL WEATHER SERVICE:
Update Since Last Briefing:
Extended the Flash Flood Watch for Atascosa, Bandera, Bexar, Frio, Gillespie, Kendall, Kerr, and Medina until 7 AM Sunday
Key Messaging Points:
Rainfall amounts of 1-3 inches with isolated pockets near 7 inches are possible as rain bands move into the region over the next 24 hours. Highest flash flood risk east of I-37 and south of I-10 through mid-morningHeavier rain will occur within rainbands, but difficult to pinpoint where bands will develop later todayFlash flooding of low water crossings, underpasses, and urban areas possibleMinor to moderate flooding expected on Rio Grande, Nueces, Frio, and San Antonio Rivers.
Area of Concern:
Coastal Plains, San Antonio metro area, portions of the Hill Country, and Rio Grande Plains
Threats & Impacts:
Rainfall: Widespread 1-3" with locally higher amounts near 7" in the Flash Flood Watch area. Several locations may experience minor flooding with flood waters capable of causing small streams, creeks, canals, and ditches to become swollen and overflow in a few places, but with little to no property damage. Quick ponding of water occurs at underpasses, low-lying spots, and poor drainage areas. Storm drains and retention ponds become near-full and begin to overflow in a few places. Flood waters may prompt brief road closures.
Bands of heavy rain will move into the region from the south today associated with the remnants of the tropical disturbance over South Texas, with flash or river flooding possible for locations that see repeated rounds of rainfall. It is still difficult to pinpoint with any certainty where these bands will set up, but the highest flash flood risk through mid-morning appears to be for areas south of I-10 and east of I-37 where one of the aforementioned bands has already set up. Rain rates may peak in the 2-2.5"/hour range today which will cause minor or flash flooding issues in urban areas. Widespread 1-3" rainfall amounts with locally higher amounts near 7" will be possible in the Flash Flood Watch area.
The heavy rain threat will begin to shift into the Rio Grande Plains overnight as the tropical disturbance moves N/NW up the Rio Grande. The latest computer models indicated the potential for rain bands to linger as far east as the San Antonio metro tonight and have extended the Flash Flood Watch for Atascosa, Bandera, Bexar, Frio, Gillespie, Kendall, Kerr, and Medina Counties. The Flash Flood Watch for the Rio Grande counties may need to be extended later into Sunday based on trends. Rain chances will decrease from east to west Sunday afternoon as the tropical disturbance exits the region.