NWS cites ‘medium probability of heavy rainfall in Valley

1 month ago 108

The National Weather Service Brownsville/Rio Grande Valley station is forecasting a medium probability of heavy rainfall in the Mid- to Lower Rio Grande Valley on Saturday, with a marginal chance of heavy rain across across all of deep South Texas and the Valley.

Meteorologists based the forecast on a frontal boundary expected to arrive Friday night and stall across the region on Saturday, combining with copious amounts of moisture from the Gulf.

“The stalled boundary along with abundant moisture will lead to the development of heavy rain and thunderstorms across the region that could lead to localized flash flooding on Saturday,” the NWS said.

“Based on the current forecast, the heaviest rain will fall Saturday morning into Saturday afternoon. The axis of highest rainfall at this time looks to fall in the mid- to lower Rio Grande Valley, though this will be highly dependent on exactly where the frontal boundary stalls or if there are any training showers or thunderstorms.”

“Training” refers to thunderstorms that pass over the same geographical area in a series, one after another like cars in a train, a situation that can produce “tremendous rainfall over relatively small areas, leading to flash flooding,” according to the National Oceanic and Atmospheric Administration.

The NWS advised of a 40% probability that 4 inches of rain or more could fall on the Mid- to Lower Valley, in addition to a marginal chance for excessive rainfall across the entire region on Saturday with a 40% chance that heavy rainfall will lead to localized flash flooding.

“Gusty winds and lightning will also be possible with this activity,” meteorologists said.

There’s at least a 5% chance heavy rains will lead to flash flooding, according to the NWS.

Meteorologists say Brownsville and Harlingen are looking at an 80% chance of precipitation, generally 1 to 2 inches, on Saturday morning and afternoon, while Edinburg, McAllen and Weslaco are looking at an 85% chance. Rain chances for Sunday are 40-50% for the region, the NWS said.

The Saturday forecast comes on the heels of the NWS outlook for May-July, which predicts hotter than normal conditions coupled with high uncertainty about the potential for rain during the period, this weekend serving as an exception.

Meteorologists warned that downpours make driving very difficult because of near zero visibility, and that nuisance flooding in poorly drained areas can occur with heavier rain bands.

As a precaution, the NWS advised that residents remove debris from drainage ditches, clean-outs and canals, while drivers should plan alternate routes away from roads that typically flood with heavy rainfall. The NWS said it would continue to update its Saturday forecast.