Texas Governor Greg Abbott has declared a state of emergency in nine counties after record-breaking rainfall on April 18 caused unprecedented flooding in the Houston area. As of 17:00 UTC (12:00 CDT), April 19, 6 people have died as a result of severe flooding.
The rain was the result of a quasi-stationary front over eastern Texas, combined with a deep flow of moisture from the Gulf of Mexico.
This slow moving system from the Midwest to the Southern Plains will continue to generate numerous showers and thunderstorms over the next couple of days, NWS warned. Flash Flood Watch is extended to Wednesday morning, April 20.
Over 304 mm (12 inches) of precipitation was reported across parts of Houston by the late April 18 as heavy downpours affected the area.
Since the late April 17, rain gauges in some areas of Harris County measured water levels close to 508 mm (20 inches), while somewhat lower amounts were recorded in other parts of southeast Texas where numerous creeks overflowed their banks.
Houston Intercontinental Airport (HIA) recorded 252.9 mm (9.92 inches) of rain on April 18, 2016.
This rainfall broke the daily record of 207.3 mm (8.16 inches) set in 1976, which was also the highest daily total ever recorded in April. Monday's rainfall ranks as the 2nd highest one-day rainfall total ever recorded by IAH, falling just 10.66 mm (0.42 inches) off the record of 262.6 mm (10.34 inches) set on June 26, 1989 (records date back to June 1, 1969). Four of the Top 10 records measured by IAH have been set since 2001.
At least thousand homes were inundated, many of them for the first time and at least 450 high-water rescues have been performed.
Deputies from the Harris County Sheriff's Department livestock unit have conducted boat rescues of over 70 horses which got trapped in raging flood waters.
The majority of the deaths were attributed to driving through flooded areas, an act which has repeatedly been warned to be extremely dangerous. Sylvester Turner, the city's major, advised residents to remain at home wherever possible and stay alert until the weather system passes.
"When you get off the freeways and off the main thoroughfares, you could be in water 3 to 4.5 m (10 to 15 feet) deep. You do not want to trap yourself in these vehicles," said Jay Evans, the Fire Department spokesman.
According to Meteorologist Sean Sublette, the magnitude of this flood event could be similar to Tropical Storm "Allison," which inundated Houston and other parts of the Southeast in June 2001.
At the time, Allison was the costliest tropical storm in U.S. history, causing $9 billion in damage. Two-thirds of Harris County received over 254 mm (10 inches) of rain from that storm with up to 508 mm (20 inches) falling in northeast Houston.
NWS warned today that a cutoff upper-level low with an associated quasi-stationary front from the Midwest to the Southern Plains will continue to generate numerous showers and thunderstorms over the next couple of days. The possibility of flash flooding will extend northward into Oklahoma and portions of southern Kansas today.
Additionally, the mountain snow in Colorado and Wyoming will taper off as the position of the upper low and surface front shifts eastward. The system is forecast to begin a slow eastward movement by Wednesday afternoon and evening when showers and thunderstorms will begin to spread into portions of the Ohio and Tennessee valleys.
Featured image credit: Mark Katz (via YT)