Port Mansfield, TX to the Rio Grande River Marine Forecast
|Tonight...Southeast Winds 5 To 10 Knots. Seas 2 Feet Or Less. Slight Chance Of Showers And Thunderstorms After Midnight.|
|Wednesday...Southeast Winds Around 5 Knots Becoming East In The Afternoon. Seas 2 Feet Or Less. Slight Chance Of Showers And Thunderstorms Through The Day.|
|Wednesday Night...Southeast Winds 5 To 10 Knots. Seas 2 Feet Or Less.|
|Thursday...Southeast Winds Around 5 Knots Becoming East In The Afternoon. Seas 2 Feet Or Less.|
|Thursday Night...Southeast Winds 5 To 10 Knots. Seas 2 Feet Or Less.|
|Friday...Southeast Winds 5 To 10 Knots. Seas 2 Feet Or Less. Chance Of Showers And Thunderstorms.|
|Friday Night...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet.|
|Saturday...South Winds 5 To 10 Knots Becoming Southeast 10 To 15 Knots In The Afternoon. Seas 2 To 3 Feet.|
|Saturday Night...South Winds 10 To 15 Knots. Seas 2 To 3 Feet.|
|Sunday...South Winds 5 To 10 Knots Becoming Southeast 10 To 15 Knots In The Afternoon. Seas 2 To 3 Feet.|
|Sunday Night...South Winds 10 To 15 Knots. Seas 2 To 3 Feet.|
| Synopsis for Baffin Bay to Rio Grande out 60 nm: GMZ100|
339 PM CDT Tue Jul 27 2021
Favorable marine conditions will persist along the Lower Texas Coast through the next several days as high pressure remains situated across the eastern Gulf of Mexico. An upper level disturbance will slide across the western Gulf of Mexico today and will help initiate showers and thunderstorms across portions of the coastal waters through the week. These may lead to locally enhanced areas of higher winds and seas.
| Area Forecast Discussion|
National Weather Service Brownsville TX
233pm CDT Tuesday July 27 2021
Short Term - Now through Wednesday night
Latest GOES-16 IR/WV satellite imagery shows a nice counter-clockwise spin of clouds and convection just off the southern Texas/northeast Mexican coast. The spin is associated with a weak mid/upper-level inverted trough that is rounding the base of a potent ridge that is centered over the central CONUS. KBRO doppler radar shows convection pulsing just east of Boca Chica/SPI and one lone thunderstorm just west of Brownsville. Latest runs of CAMs don't really pick up this on-going convection, so will have to monitor trends over the next couple of hours to see if they are able to move onshore or if additional development occurs inland.
The aforementioned inverted trough will continue to retrograde westward and move onshore over northeast Mexico/Deep South Texas Wednesday morning. This will keep a slight chance of showers and thunderstorms in the forecast through the rest of the short-term period. Despite MOS guidance keeping Probability of Precipitation at or below 15% (with the exception of ECM) for tomorrow, decided to keep Probability of Precipitation around 20%, best chances occurring in the afternoon as daytime heating occurs and possibly enhances sea breeze activity. As mentioned in the previous AFD, PWATs (Precipitable Waters) will remain generally below 2.0 inches and therefore not expecting a washout with any convection that is able to get going. Otherwise, expect mostly clear to partly cloudy skies to continue. Temperatures will remain near seasonal average for late July, with tonight and Wednesday night's lows in the mid-upper 70s and highs tomorrow in the mid-upper 90s to lower 100s in Zapata and western Starr counties. Heat indices will range between 105 to 110 degrees along and west of I-69E tomorrow afternoon.
Long Term - Thursday through Tuesday
A broad 500mb high will be centered over the central US to begin the long term period. Deep South Texas will wind up along the southern periphery of the high, where a few weak midlevel disturbances will bring some low-end chances for showers and thunderstorms as they move westward on Thursday and Friday. Heading into the weekend, midlevel longwave troughing will set up over the eastern Pacific and the northeastern United States, helping to amplify the midlevel pattern amplitude while also pushing the ridge axis westward to set up over the Rockies. The 500mb ridge will be the primary influence on weather across the Rio Grande Valley this weekend and early next week with hot and dry conditions expected through next Tuesday. Temperatures will top out near-to-slightly-above normal through early next week, while surface moisture is expected to remain plentiful due to persistent southeasterly surface flow associated with surface high pressure over the Gulf. The combination of these will lead to heat indices routinely reaching 105-110 degrees across much of the CWA, with Heat Advisory conditions possible for Starr and Zapata counties through the end of the period.
Marine - Now through Wednesday night
Favorable marine conditions are expected to continue through Wednesday night with a weak pressure gradient in place. Wave heigheights will generally be 2 feet or less on the Gulf waters with light to moderate easterly or southeasterly winds. A weak mid-level trough will gradually move inland over Deep South Texas on Wednesday, keeping the chance for some isolated to scattered showers and thunderstorms across the waters tonight and through the day on Wednesday. SCEC and SCA (Small Craft Advisory) conditions are not expected.
Thursday through Sunday: High pressure will set in over the central and eastern Gulf of Mexico on Thursday and then be very slow to move through the end of the period. This will favor a weak surface pressure gradient over the Gulf leading to light to moderate southeast winds and low wave heights. Some showers and thunderstorms will be possible on Thursday and Friday which may lead to locally enhanced areas of winds and seas. Weak low pressure may develop over the Central Plains late Saturday into Sunday, which may tighten the pressure gradient just enough to push winds into low-end SCEC conditions, but this will be a fairly brief period of higher winds.
NOAA Brownsville TX Office: Watches - Warnings - Advisories