Sunrise 6:41 AM   Sunset 8:11 PM Moonrise 2:15 PM   Moonset 2:18 AM

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GMZ130 Laguna Madre From The Port Of Brownsville To The Arroyo Colorado- Laguna Madre From The Arroyo Colorado To 5 Nm North Of Port Mansfield Tx- Laguna Madre From 5 Nm North Of Port Mansfield To Baffin Bay Tx- 411 Am Cdt Fri May 17 2024
Today - East winds 5 to 10 knots becoming northeast this afternoon. Light chop on the bay. Patchy fog this morning. Hazy. A slight chance of Thunderstorms this morning. A chance of showers. A chance of Thunderstorms this afternoon. Tonight - East winds 5 to 10 knots. Light chop on the bay. A slight chance of showers and Thunderstorms after midnight. Saturday - Northeast winds around 5 knots increasing to 5 to 10 knots in the afternoon. Smooth on the bay becoming light chop in the afternoon. Saturday night - East winds 5 to 10 knots. Light chop on the bay. Sunday - East winds 5 to 10 knots. Light chop on the bay. Sunday night - Southeast winds around 10 knots. Light chop on the bay. Monday - Southeast winds 10 to 15 knots. A moderate chop on the bay. Monday night - Southeast winds 10 to 15 knots. A moderate chop on the bay. Tuesday - Southeast winds 10 to 15 knots increasing to 15 to 20 knots in the afternoon. A moderate chop on the bay becoming choppy in the afternoon. Tuesday night - Southeast winds 15 to 20 knots becoming south 10 to 15 knots after midnight. Choppy on the bay becoming a moderate chop after midnight.
winds and waves higher in and near Thunderstorms.

GMZ100 411 Am Cdt Fri May 17 2024
Synopsis - Light to moderate easterly winds will prevail for much of the period. There is a slight chance for showers and Thunderstorms for the northern portions of the laguna madre and nearshore (0-20 nm) gulf water this morning, which will expand south and eastward throughout the day with additional chances later this afternoon/evening, as a stationary boundary meanders over the area into Saturday.

FXUS64 KBRO 170910 AFDBRO

Area Forecast Discussion National Weather Service Brownsville TX 410 AM CDT Fri May 17 2024

New SHORT TERM, LONG TERM, MARINE

SHORT TERM
(Today through Saturday)
Issued at 407 AM CDT Fri May 17 2024

Key Messages:

* Low to medium (20-50%) chance for showers and thunderstorms today (greatest chance Northern Ranchlands)

* All of Deep South Texas including the Rio Grande Valley is under a Marginal (Level 1 out of 5) Threat for Severe Thunderstorms today

* Saturday will mark the beginning of another stretch of very warm and hot conditions

The main forecast concern for Deep South Texas and the Rio Grande Valley will be the potential for showers and thunderstorms today and again later this afternoon/evening. A stalled out cold frontal boundary over the Northern Ranchlands and a shortwave overhead will be the focus of showers and thunderstorms potentially developing over the local forecast area today. Currently, there is a low to medium chance ranging from 20-50% for showers and thunderstorms today with the lower chances along the Rio Grande Valley and the higher chances over the Northern Ranchlands (in closer proximity to the aforementioned frontal boundary).

With the local forecast area placed on/near the right entrance region of an 80-100 kt jet overhead, Showalter values indicating a moderately to very unstable atmosphere, MLCAPE values between 500- 1,000 J/kg, MUCAPE values between 1,000-3,000 J/kg, and decent mid- level lapse rates of around 7C/km, there is enough large scale forcing and instability in place for storms to develop.
Additionally, with 0-6km bulk shear values between 50-60 kts, any storms that develop will have the potential for becoming strong to severe with the capabilities of some hail and/or damaging winds.
Given the overall atmospheric dynamics and synoptic pattern in place, all of Deep South Texas and the Rio Grande Valley run the risk of isolated severe weather today. The Storm Prediction Center (SPC) in Norman, OK has placed the entire area under a "Marginal (Level 1 out of 5) Risk" for severe weather today. Again, the main threats will be isolated damaging wind gusts and hail. Finally, any storms that do form will also have the capabilities of producing heavy rainfall with PWAT values between 1.75-2.30 inches (1 to 3 STDEVs above normal).

Otherwise, expect for today to be mostly cloudy, warm, humid, and hazy. High temperatures are expected to range between 90-95F this afternoon (cooler near/along the coast due to continued onshore flow out of the east-northeast).

The storm threat comes to an end later this evening/tonight as the frontal boundary lifts northward and high pressure begins to strengthen. Tonight will once again be another warm and muggy night.
Given the copious amounts of low level moisture in place, some patchy mist/fog is also possible once again tonight as well. Low temperatures are expected to be in the 70s most places with similar dewpoint values (narrow dewpoint depressions).

After a day of relatively cooler temperatures, Saturday will begin another stretch of very warm to hot days as forecast models and ensembles show ridging strengthening and 500 mb geopotential heights increasing over the region. During the day on Saturday, the northern fringe of a 591 dam heat dome will encompass most, if not all of the area. Additionally, the 1000-500 mb thickness values increase over the area as well with values returning to around 580 dam. This implies 850 mb temperatures reaching the lower 20s (degree Celsius)
which will translate to surface temperatures in the mid 90s to near lower 100s on Saturday across Deep South Texas and the Rio Grande Valley. This coupled with dewpoints in the 70s will result in heat indices ranging between 103-111F on Saturday (just below Heat Advisory criteria).

LONG TERM
(Saturday night through Thursday)
Issued at 407 AM CDT Fri May 17 2024

Mid-level ridging will build over Texas through the period leading to warming temperatures with triple digits across the Rio Grande Plains on Sunday afternoon with mid to upper 90s across the rest of the area, except for the 80s near the coast. The triple digits will expand eastward through the week, reaching the I-69c/US 77 corridor by Tuesday. High humidity combined with the hot temperatures will lead to "feels like" temperatures exceeding 110 degrees in many areas and Heat Advisories will likely be needed Monday through Friday. Overnight temperatures each night will remain warm with lows falling into the upper 70s to low 80s. The NWS HeatRisk tool highlights a major risk of heat-related impacts for those that are not properly hydrated or do not have effective cooling in place through the week. The combination of lack of moisture and subsidence will generally maintain rain-free conditions across Deep South Texas through the long term.

AVIATION
(06Z TAFS)
Issued at 1246 AM CDT Fri May 17 2024

Through 06z Sunday....MVFR conditions were taking place at the TAF sites under a SCT-BKN deck of stratus clouds with ceilings between 1,000-1,500 feet AGL and haze which is restricting visibilities down to 4-6 statute miles. Much of the TAF period including the next 6-9 hours will continue to experience MVFR cigs and/or visibilities. There could be times especially during the day today where VFR conditions are seen.

There is a non-zero, low grade probability of showers and thunderstorms to develop this morning and then again this afternoon/evening as a frontal boundary approaches. Opted to keep headlines out of the TAFs given the continued uncertainty with the likelihood and coverage of storms. If confidence for storm chances increase in the hours ahead, will make amendments in the form of a TEMPO or Prob30 to the TAFs to reflect the increase confidence.

Winds are currently out of the southeast at 5-10 kts. An outflow boundary from earlier convection to our north could shift winds out of the east-northeast towards daybreak. Otherwise, expect for light and variable winds during the morning hours. During the afternoon hours today, expect for winds to become east-northeasterly between 5- 10 kts.

MARINE
Issued at 407 AM CDT Fri May 17 2024

Today through Saturday: Light to moderate winds will yield low to moderate seas today through Saturday. While marine conditions are mostly favorable today through Saturday, there remains a "Moderate Risk" for rip currents along the are beaches through Saturday.

Saturday night through Thursday: Light to moderate winds with moderate seas of generally 3 to 5 ft will persist through late in the week. A slighlty enhanced pressure gradient each afternoon, especially next week, could lead to periods of Small Craft Caution.

PRELIMINARY POINT TEMPS/POPS
BROWNSVILLE 92 78 94 78 / 20 20 10 0 HARLINGEN 92 75 95 75 / 30 20 10 0 MCALLEN 94 77 98 78 / 40 20 10 0 RIO GRANDE CITY 92 74 99 76 / 40 20 0 0 SOUTH PADRE ISLAND 85 80 85 80 / 20 30 10 0 BAYVIEW/PORT ISABEL 88 77 90 78 / 30 20 10 0

BRO WATCHES/WARNINGS/ADVISORIES
TX...None.
GM...None.

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Matamoros
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Fri -- 02:18 AM CST     Moonset
Fri -- 04:55 AM CST     0.34 feet Low Tide
Fri -- 05:42 AM CST     Sunrise
Fri -- 12:02 PM CST     0.85 feet High Tide
Fri -- 02:15 PM CST     Moonrise
Fri -- 06:13 PM CST     0.40 feet Low Tide
Fri -- 07:10 PM CST     Sunset
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Matamoros, Tamaulipas, Mexico, Tide feet

Port Isabel
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Fri -- 03:17 AM CDT     Moonset
Fri -- 05:45 AM CDT     0.49 feet Low Tide
Fri -- 06:41 AM CDT     Sunrise
Fri -- 12:53 PM CDT     1.05 feet High Tide
Fri -- 03:13 PM CDT     Moonrise
Fri -- 07:52 PM CDT     0.65 feet Low Tide
Fri -- 08:09 PM CDT     Sunset
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Port Isabel, Texas, Tide feet

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