A flood watch is in effect for Collin County, putting Murphy, Wylie and Sachse in the path of heavy rain.
The National Weather Service in Fort Worth issued the watch at 4 p.m. Wednesday, Sept. 30, warning of 2 to 4 inches of rain through Thursday night. Isolated totals could reach 6 to 7 inches where storms stall over the same areas. The watch runs through Friday morning and covers counties along and west of Interstate 35, including Dallas, Tarrant, Denton, Collin, Ellis and Parker counties.
The rain is fueled by leftover tropical moisture from Hurricane Polo, which struck Mexico's Baja California Sur on Tuesday, Sept. 29, with 110-mph winds before weakening inland. That moisture is now merging with a separate Pacific low-pressure system, according to Marc Chenard, a senior branch forecaster at the U.S. Weather Prediction Center.
"Those two features combined will bring a pretty wide flood threat spread into the Plains," Chenard told Bloomberg, as Insurance Journal reported.
The Weather Prediction Center has placed a moderate risk of excessive rainfall, level 3 of 4, over parts of Texas including Dallas for Wednesday and Thursday.
Dry soil raises flash flood risk
The region is especially vulnerable. KRLD reported that DFW International Airport went 67 consecutive days without measurable rain from mid-July through Sept. 21, tying the second-longest dry streak on record. August recorded zero measurable rain at the official climate site.
That prolonged drought baked the soil hard. The NWS says rainfall will run off quickly rather than soak in, accelerating flash flood risk in low-lying areas, along creeks and streams, and at low-water crossings.
Severe weather possible Wednesday evening
The NWS Fort Worth office warned that storms Wednesday evening could turn severe, mainly near and west of I-35. Heavy rain and damaging winds are the primary threats, but forecasters said small hail and a brief tornado cannot be ruled out. Wind gusts could reach 35 mph.
Showers and storms are expected to continue Thursday and Friday, with the heaviest coverage through Thursday night before tapering from west to east on Friday.
State response
Gov. Greg Abbott activated additional emergency resources on Monday, Sept. 28, directing the State Emergency Operations Center to begin 24/7 operations. More than 1,900 state responders and over 1,500 pieces of equipment are available statewide, including swiftwater rescue teams, high-profile vehicles, Black Hawk helicopters and Texas National Guard personnel, according to the governor's office.
What Murphy, Wylie and Sachse residents should do
The NWS Fort Worth office urged residents to have multiple ways to receive warnings, because flash flooding can escalate quickly. Six inches of moving water can knock a person down. A foot of moving water can sweep away a vehicle.
The NWS urges residents not to drive through flooded roadways, even if the water appears shallow.
Residents can check real-time road conditions at DriveTexas.org, find severe weather preparedness information at TexasReady.gov and access flood data at TexasFlood.org.
