Port Mansfield, TX to the Rio Grande River Marine Forecast
|Today...Southeast Winds 5 To 10 Knots Increasing To 10 To 15 Knots In The Afternoon. Seas 2 Feet Or Less Building To 2 To 3 Feet In The Afternoon.|
|Tonight...South Winds 5 To 10 Knots. Seas 2 To 4 Feet. Patchy Fog After Midnight.|
|Thursday...South Winds 5 To 10 Knots Becoming Southeast 10 To 15 Knots In The Afternoon. Seas 2 To 3 Feet Subsiding To 2 Feet Or Less In The Afternoon. Slight Chance Of Showers And Thunderstorms In The Afternoon.|
|Thursday Night...East Winds 5 To 10 Knots Shifting Northeast After Midnight. Seas 2 To 4 Feet. Slight Chance Of Showers And Thunderstorms.|
|Friday...Northeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Slight Chance Of Showers And Thunderstorms.|
|Friday Night...Southeast Winds 10 To 15 Knots. Seas 4 To 6 Feet With Occasional Seas Up To 7 Feet.|
|Saturday...Southeast Winds 10 To 15 Knots. Seas 3 To 5 Feet.|
|Saturday Night...Southeast Winds 5 To 10 Knots Shifting Southwest After Midnight. Seas 3 To 5 Feet. Slight Chance Of Showers And Thunderstorms.|
|Sunday...Northwest Winds 5 To 10 Knots Shifting North In The Afternoon. Seas 3 To 5 Feet.|
|Sunday Night...East Winds 5 To 10 Knots Shifting South After Midnight. Seas 4 To 6 Feet With Occasional Seas Up To 7 Feet.|
Synopsis for Baffin Bay to Rio Grande out 60 nm: GMZ100|
341 AM CDT Wed Apr 8 2020
Marine conditions will remain generally favorable this week as high pressure maintains a weak pressure gradient across the lower Texas coast. Patchy fog may develop across the Laguna Madre and nearshore coastal waters early Thursday morning. Winds and seas will increase slightly behind a weak cold front that is expected to move through Saturday night into Sunday. Adverse conditions are not expected through the forecast period at this time, but small craft may need to exercise caution this weekend with the frontal passage.
Area Forecast Discussion|
National Weather Service Brownsville TX
439am CDT Wednesday April 8 2020
Short Term - Now through Thursday
Deep South Texas and the Rio Grande Valley will continue to be under a southwesterly flow aloft as the mid-level ridge remains over the Gulf of Mexico. With the approach of a deep 500 mb cutoff low from the west, the ridge over the Gulf will begin to flatten, and a mid-level vorticity maximum will pass over Central/South Texas this afternoon. Forecast soundings show moderate to high instability across the extreme western portion of deep South Texas, especially across Zapata county where CAPE values exceed 2500 J/kg with little to no cap this afternoon. Heading towards the coast, the cap increases, so slight rain/thunderstorm chances will be confined primarily to Zapata County this afternoon/evening. The Storm Prediction Center has included this area in a Marginal Risk for isolated severe thunderstorms today, with the biggest threat being large hail, but strong wind gusts could be possible. Temperatures will reach the low to mid 90s this afternoon, aiding in the increased instability, with light to moderate southeast surface winds. Tonight, rain chances continue out west, with the potential for patchy fog for the coastal counties and offshore towards the early morning hours. Lows tonight will generally be in the lower to mid 70s.
Another, stronger mid-level vorticity maximum will pass over Central/South Texas ahead of the 500 mb low, in conjunction with an approaching cold front on Thursday. This front is expected to stall just north of deep South Texas, but the northern ranchlands could still see a prefrontal wind shift. The Storm Prediction Center has included areas of deep South Texas west of I-69C in a Slight Risk for severe weather, with the rest of deep South Texas and the Rio Grande Valley in a Marginal Risk. With temperatures reaching the lower to mid 90s again on Thursday with southeasterly surface winds bringing in ample low level moisture, instability will increase with a minimal cap in the afternoon on Thursday. The primary threat will once again be large hail, but strong wing gusts are still possible. The positioning and timing of the approaching cold front will play a big role in initiating convection, so will continue to monitor these trends.
Long Term - Thursday Night through Tuesday
The forecast period starts with a bang. Per the Day 2 Convective Outlook issued by the Storm Prediction Center, the entire BRO CWFA is under a Marginal to Slight Risk of severe weather Thursday night until around sunrise Friday morning. Since this is a relatively new development, will not include the mention of strong to severe thunderstorms in the official forecast, but will include it in the forthcoming Hazardous Weather Outlook and allow successive shifts to monitor trends. Additionally, the Day 3 Convective Outlook places a Marginal Risk of severe weather for roughly the western third of the BRO CWFA for Friday until sunrise Saturday morning. Overall, the entire forecast period will be unsettled courtesy of the severe weather threat and the passage of a trio of cold fronts, which will produce a rollercoaster effect of daytime high and overnight low temperatures.
Marine - Now through Thursday
With a surface ridge over the eastern Gulf of Mexico, expect generally favorable marine conditions through the short term with light to moderate southeasterly winds and wave heigheights of 1 to 3 feet across the lower Texas coastal waters. Patchy fog will be possible Thursday morning, primarily for the Laguna Madre and nearshore waters out 20 nm.
Thursday Night through Tuesday: Less than ideal marine conditions are expected through a majority of the period due to the passage of a trio of cold fronts. Small Craft Exercise Caution and/or Small Craft Advisory are likely Friday night through Tuesday due to winds and/or seas.
NOAA Brownsville TX Office: Watches - Warnings - Advisories