Much Less than For Recent Flood
The National Weather Service Brownsville/Rio Grande Valley has reported the next rainfall event will not be anything like the persistent event of last week that created widespread flooding across the Rio Grande Valley.
A steadily moving upper level disturbance whose center reached the coast north of Tampico this morning will move through north east Mexico through Monday before dissipating in north central Mexico Monday night and early Tuesday. On the "backside" of the disturbance, a brief period of deep tropical moisture combined with sufficient lift will bring a cluster or band of showers/thunderstorms between late tonight and midday Monday, with another possible round Monday night into early Tuesday. The Monday round should come in through the Gulf and reach the Lower/Mid Valley - mainly along/east of US 281/IH 69C. The second round late Monday night/early Tuesday favors areas along/west of US 281/IH 69C.
Drier air will filter into the area Tuesday with sunshine returning; upper level subtropical high pressure will take over thereafter and continue through next weekend. A few sea breeze showers and perhaps a stray thunderstorm may stream northwest mainly in Cameron, Willacy, Kenedy, eastern Hidalgo, and eastern Brooks County from late morning through early afternoon Wednesday and Thursday with minimal impact; breezy, hot, rain-free weather is expected Friday through next Sunday.
This rain will be more an aggravation or nuisance than anything else.
While they cannot rule out local, quick hitting nuisance urban flooding, they do not expect widespread high water in poorly draining locations.
What to Watch For
0.25 to 0.75" is expected on average, favoring the Lower/Mid Valley from the pre-dawn hours through early afternoon Monday
Reasonable worse case scenario: Persistent bands drop 1 to 3 inches in local, not widespread, areas. Exactly which areas is impossible to determine now.
Another round will favor the upper Valley and Rio Grande Plains Monday night, but confidence on its occurrence is medium, and intensity is low.
Potential Impacts/Recommended Actions
With most areas having drained out/dried sufficiently over the weekend, additional flooding from the "reasonable worse case scenario" events (1 to 3 inches) would be of the 'nuisance' variety
This could result in 1 to 2 feet of water depth in poor draining locations
If there are any recent debris-clogged canals, pipes, clean-outs, etc. due to last week's flows, attempts to clear the debris should be made today (Sunday) as it would not take much for flooding to begin
Monday morning commuters should have alternate routes in mind today (Sunday), just in case minor flooding begins
There is no need to panic. Only to prepare for the potential for locally nuisance flooding for a much shorter time period - the typical guidance we give for spring, summer, and autumn thunderstorm cluster or thunderstorm band development.