822 FXUS64 KBRO 071122 AAA AFDBROArea Forecast Discussion...UPDATED National Weather Service Brownsville TX 622 AM CDT Sun Sep 7 2025
...New AVIATION...
.DISCUSSION... Issued at 1025 PM CDT Sat Sep 6 2025
The main focus for this forecast period continues to be the elevated chances for rain continuing through the early part of next week. Current model guidance does show that there is a large plume of moisture that will make its way into Deep South Texas and the Rio Grande Valley tomorrow. This will allow for PWATs to be around 2 inches through the early part of the week. The values of these PWATs would be in the 90th percentile. Meanwhile, a frontal boundary is expected to stall out to the north of the region. With southeasterly to easterly flow on the surface, there will be plenty of low-level moisture in the region to foster the development of showers and thunderstorms over the region.
There are several factors to this rainfall event that bring a lot of uncertainty to the forecast. Notably, how far south the front comes down will be a major factor as the further south the front comes down the greater chances for rain would be for the region. However, if the front stays further north, the chances for rain could drop for the area. Another factor will be how the seabreeze and any outflow boundaries affect the development of showers and thunderstorms. The interactions of the seabreeze and the outflow boundaries are expected to be the main drivers for the development of showers and thunderstorms with this event. Given the amount of uncertainty in the forecast, it is hard to say which locations are likely to be impacted the most at this time. With so much uncertainty in the forecast, a blend of the NBM, CONSALL, and ECMWF were used to lower PoPs and to reduce some of the bias that is in the NBM blends. Any sort of persistent rain over any area could lead to some localized flooding especially for places in low-lying areas and other flood prone regions. It should also be noted that given the high amount of moisture in the environment, it is possible for some of these showers and thunderstorms to produce a high amount of rainfall in an area in a very short time, that could also lead to some localized flooding as well. With all these factors combined, WPC maintains a marginal risk (level 1 of 4) for excessive rainfall for Deep South Texas and the Rio Grande Valley.
As for the temperatures in the forecast period, the highs for today and tomorrow are expected to mostly be in the triple digits for the region with areas along the coast could be in the upper 90s. However, moving into the weekend and the rest of the forecast period, temperatures are expected to decrease a bit due to the cloud coverage over the area. Limiting the highs to mid to upper 90s for the area. Low temperatures are expected to mostly remain in the 70s for the forecast period as well.
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.AVIATION... (12Z TAFS) Issued at 618 AM CDT Sun Sep 7 2025
Only minor adjustments needed to the previous issuance of TAFs. A TEMPO for convection remains based on the HRRR model guidance. Overall, VFR is anticipated through the next 24 hours.
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.MARINE... Issued at 1025 PM CDT Sat Sep 6 2025
Mostly favorable marine conditions are expected for the forecast period with light to moderate southeasterly to easterly winds and low to moderate seas. Showers and thunderstorms are expected to be more likely through the early part of next week. A frontal boundary is expected to stall out towards the north of the Lower Texas Coast. Depending on how far north the front stalls out, will impact the chances for rain.
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.PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 91 78 90 77 / 60 60 60 40 HARLINGEN 92 74 92 73 / 70 60 70 30 MCALLEN 94 77 93 76 / 70 70 60 20 RIO GRANDE CITY 93 74 93 73 / 70 70 60 20 SOUTH PADRE ISLAND 88 80 87 81 / 70 70 70 40 BAYVIEW/PORT ISABEL 90 77 90 76 / 70 70 60 30
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.BRO WATCHES/WARNINGS/ADVISORIES...None.
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NWS BRO Office Area Forecast Discussion