A flash flood warning means that flooding is imminent or occurring.
Flash Flood Warning including San Marcos TX, Kyle TX, Lockhart TX until 4:45 AM CDT pic.twitter.com/nK0xCV6SIp
— NWS San Antonio (@NWSSanAntonio) August 27, 2017
Update 6:58 a.m. Saturday: San Marcos, Hays County under tropical storm warning for the next 36 hours
Hays, Guadalupe and Comal Counties are now also under a tropical storm warning.
The National Weather Service says to expect very heavy rainfall over the next several days and tropical storm winds of 40-50 miles per hour with gusts up to 60 miles per hour.
557 AM: Flood Advisories are in effect for locations in the green polygons. pic.twitter.com/lN5MgKktq9
— NWS San Antonio (@NWSSanAntonio) August 26, 2017
Update 11:20 a.m. Friday: The National Weather Service has placed the city of San Marcos under a tropical storm warning for the next 36 hours in anticipation of Hurricane Harvey.
NWS said there is currently a moderate threat to life and property, with winds predicted at 25-35 miles per hour and gusts up to 45 miles per hour.
Hays County is also under a flash flood warning.
The moisture from Harvey is expected to bring widespread heavy rain and flooding to southeast Texas starting Friday and continuing through the weekend. Major flooding is possible.
Here's how you can get prepared for Hurricane Harvey.
Original post: Hays County under flash flood watch due to Tropical Storm Harvey starting Friday
The National Weather Service has issued a flash flood watch in Hays, Bastrop and Lee counties from Friday afternoon through Sunday morning.
NWS predicts "copious amounts of rain" starting Friday afternoon and lasting through at least Sunday morning as Tropical Storm Harvey moves onshore.
The earlist the storm could arrive in South Central Texas could be Friday afternoon.
The watch may be expanded past Sunday as meteorologists predict Harvey will linger in the area through the weekend, bringing more rainfall.
NWS said rainfall totals through early next week will average 8-15 inches with isolated higher totals possible.
George Hatt, a spokesperson with the city of San Marcos, said the city is monitoring weather conditions and readying first responders and on-call personnel for possible heavy rain or flooding. If needed, she said the city would activate its emergency operations center and coordinate closely with state and local agencies.
Citizens can sign up for emergency notifications at www.sanmarcostx.gov/alerts.
Kharley Smith, Hays County emergency management coordinator, said county personnel is on standby and has been in coordination with neighboring counties and the Texas Division of Emergency Management.
"At this point, we don't know exactly where Harvey will make landfall or how far inland heavy rains may cause issues," she said. "We are well-prepared for problems caused by weather as well as ready to take in evacuees from coastal areas if that becomes necessary."
The Texas Department of Transportation plans to have 20 maintenance crews on-site to help with cleanup following the storm.