Marine Weather Net

Port Mansfield, TX to the Rio Grande River 20 - 60 NM Marine Forecast


10 - 15


10 - 15


10 - 15


10 - 15

The Marine Weather Forecast In Detail:
GMZ170 Forecast Issued: 938 AM CDT Sat Aug 08 2020

Today...Southeast Winds 10 To 15 Knots Diminishing To 5 To 10 Knots In The Afternoon. Seas 2 To 4 Feet. Isolated Thunderstorms In The Morning. Scattered Showers Through The Day. Scattered Thunderstorms In The Afternoon.
Tonight...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Isolated Showers After Midnight.
Sunday...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Isolated Showers In The Morning.
Sunday Night...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Slight Chance Of Showers And Thunderstorms After Midnight.
Monday...Southeast Winds 5 To 10 Knots Increasing To 10 To 15 Knots In The Afternoon. Seas 2 To 4 Feet. Slight Chance Of Showers And Thunderstorms In The Morning.
Monday Night...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Slight Chance Of Showers And Thunderstorms After Midnight.
Tuesday...Southeast Winds 5 To 10 Knots Increasing To 10 To 15 Knots In The Afternoon. Seas 2 To 4 Feet. Slight Chance Of Showers And Thunderstorms.
Tuesday Night...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet.
Wednesday...Southeast Winds 5 To 10 Knots Increasing To 10 To 15 Knots In The Afternoon. Seas 2 To 3 Feet.
Wednesday Night...Southeast Winds 10 To 15 Knots. Seas 2 To 3 Feet.
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Synopsis for Baffin Bay to Rio Grande out 60 nm: GMZ100
938 AM CDT Sat Aug 8 2020

High pressure centered over the northeastern Gulf of Mexico, with ridging extending westward, will drive light to moderate southeasterly winds and generally low seas through the middle of next week. A weak upper level disturbance will also bring scattered showers and thunderstorms to the coastal waters today.
Area Forecast Discussion
...UPDATED National Weather Service Brownsville TX
631am CDT Sat August 8 2020

Short Term - Today Through Sunday
nly cosmetic adjustments to the forecast were needed for the short-term. Still expecting today to have the best chances of rain for the next week or so. Spotty nocturnal showers (though not really showing the elongated nature of "streamers") already showing up on KBRO radar. Well-advertised, though modest, mid-upper level inverted trough shows up well on GOES- 16 water-vapor imagery. Model progs indicate H5 temps of around -5C by this afternoon, which would represent ~2.5C of cooling from the value observed on last evening's 00Z KBRO sounding. This will be enough to enhance the shower coverage generated by the sea-breeze over that observed over the past couple days. Some thunder is also expected, particularly during the middle part of the day, as the sea- breeze marches inland and outflow boundaries from the first storms possibly collide. Raised PoP's by 5% between 15-21Z, more into the middle range of scattered category. Brief heavy downpours are possible, as precipitable water values peak at ~2.0".

For temperatures, we are now into the climatologically hottest portion of the year, and again have not strayed far from persistence. Most folks will see highs in the mid-90s, with readings again nearing 100F in the Falcon Lake/Zapata vicinity. McAllen should be a couple degrees lower than climo, actually, presumably due to some of the wetter ground in that area, but still around 96-97F.

Yet another warm and muggy one for Saturday night. Model guidance, across the board, really shuts down rain chances after 00Z with the loss of daytime heating. A lower-grade sea-breeze convective regime continues Sunday, with more isolated coverage anticipated, as the weak mid-level disturbance weakens and moves inland. Both NAM and GFS indicate some drying of the column, with PW falling below normal (to ~1.5"), so any showers should not be particularly heavy. Thicknesses change little for Sunday, as mid-level high center migrates from north-central Texas toward the ArkLaTex nexus. Temps perhaps tick up a degree with more sunshine expected. Heat indices reach 103-108F, but nothing out of the ordinary for early-mid August.

Long Term - Sunday Night through Friday
Only subtle changes made to the forecast for next work week. The dominant feature remains the broad and southwestern U.S. high pressure ridge which stretches from west to east from the New Mexico/Arizona border region into Chihuahua/Sonora on east into much of Texas. While the ridge is close to the traditional "La Canicula" (Dog Days) position...which is typically southeast New Mexico and west Texas into Chihuahua and Coahuila Mexico...the axis remains more north to south rather than northwest to southeast. This positioning will continue to open the door to east/northeast flow aloft across the Texas and northeast Mexican coast, which *may* be enough to nudge deeper moisture into the lower Rio Grande Valley and northeast Mexico through Tuesday. ECMWF (European Centre for Medium-Range Weather Forecasts) and to a lesser degree GFS hint at the northern edge of a very weak inverted trough (aloft) could enhance rain chances Monday...but confidence just isn't there to make wholesale adjustments so have kept status quo (20 percent, shifting from near the coast to a little inland during the day) for rain chances.

Moisture looks to be trimmed Wednesday And Thursday
and that combined with continued soil moisture drying should be enough to remove mentionable rain chances. Did keep very minor chances on Thursday but these too could be removed in due time. By next Friday...models continue to hint at an inverted trough sliding west toward the coast but it's not all that much at this maintained the slightly larger area but still low mentionable (20 percent) rain chances for now.

Made no changes to temperature forecast at this time. Would not surprise if Tuesday to Friday maximums need to be raised a degree as drying ground and atmosphere support seasonal averages (, particularly in Hidalgo County where the (still) wet soils have kept afternoon temperatures closer to the mid than upper 90s this week. Even so...not seeing triple digit readings in the Hidalgo/Cameron/Willacy County just yet next week. About the only change was to tweak up afternoon and early evening southeast winds as mixing and gradient should increase the fresh breeze factor when the sea breeze enhances it. Bottom line? It's August and it will continue to feel like it.

MARINE: (Today through Sunday...Boaters should be aware of scattered showers and thunderstorms today, but otherwise, winds and seas should remain favorable. High-pressure ridge extending across the Gulf of Mexico will continue to provide a light-to- moderate SE onshore flow. Gulf seas, currently only about 2 ft., per TABS-K buoy, build just slightly to around 3 ft. by tonight due to a modest fetch of SE flow persisting.

Sunday Night through Wednesday Night: What you see is what you get...diurnal shifts from land to sea and back again but little more than freshening afternoon winds on Laguna Madre and evening winds over at least the nearshore waters. Could nudge toward caution levels at favored diurnal times but for now have capped speeds at 15 knots during these times...with lighter winds (5 to 10 knots) late night through around noon each day. The more persistent southeast flow will slowly build seas...but moderate levels (3 to 4 feet) are all that's expected now.

NOAA Brownsville TX Office: Watches - Warnings - Advisories
TX...None. GM...None.