Forecast: Flash floods possible as chances of heavy rain expected

(National Weather Service)

The National Weather Service in Brownsville has issued a flood watch for three Rio Grande Valley counties as storms are expected to threaten the region on Thanksgiving.

The flood watch will be in effect from Thursday morning until afternoon for Cameron, Hidalgo and Willacy counties. The NWS reports flash flooding by excessive rain is possible.

Cities included in the watch are Raymondville, Weslaco, Sarita, Laguna Vista, Edinburg, Port Mansfield, Pharr, Mission, Port Isabel, McAllen, South Padre Island, San Manuel, Laguna Heights, Falfurrias, Harlingen, and Brownsville.

A cold front is expected to arrive in the Valley on Thursday that will be accompanied by heavy showers and thunderstorms.

“We are looking at getting some significant rainfall…it’s going to be closer to coastline of where we think the main threat is going to be,” said Tim Speece, a senior forecaster with the NWS, on Wednesday. “We are thinking anywhere along and east of the I-69C corridor is where we are expecting the heaviest rainfall.”

Some areas of the Valley could receive up to 4 inches of rain during the long holiday weekend.

Although forecasters don’t anticipate there will be hail or strong winds, the main threat will be from the heavy rainfall. “It’s going to be rainfall, showers, moderate to heavy showers with embedded thunderstorms,” Speece said.

Residents living in Brownsville, Port Isabel, South Padre Island, Laguna Heights and Laguna Vista should especially monitor the weather on Thursday, Speece said, since “the highest rainfall amounts we are participating will be in Cameron County.”

Motorists planning to travel across the Valley on Thursday are encouraged to stay abreast of the weather forecast and to monitor the NWS’s social media pages for any alerts that may be issued.

“They should allow themselves plenty of extra time to get wherever they are headed to, don’t speed and if they start to enter into heavier rainfall it’s always a good idea to pull off the road and let the rainfall pass,” Speece said. “We would rather people get there late versus have an accident.”

The cold front is expected to arrive in the Valley sometime in the late afternoon or evening hours of Thursday. It will clear the Brownsville area a little after sunset.

“The time period that we are concerned about the most would be the afternoon and into the early evening hours,” Speece said.

Once the cold front passes through, there’s the possibility that rainfall will linger in the area into Friday. Rainfall chances for Saturday and Sunday will be low. The potential for severe weather is low.

It’s not common to have rain in the month of November since the Valley gets the bulk of its rainfall in September and October. “For it to last into the holidays and into November, that is usually not the case. We normally are not seeing heavy rainfall like this,” Speece said.

The rain was expected to begin Wednesday night when there’s a 30% chance of showers.

The rain chances increase to 60 to 90% on Thursday with 1 to 2 inches of rain possible.

The Thanksgiving Day temperatures will be around 81 degrees with the Thursday’s night’s temperatures dropping to the low 50s with a 70% of showers on Thursday night.

Friday’s highs will be around 62 degrees with a 40 percent chance of showers. The lows on Friday night will be around 52 degrees with a 20% chance of showers.