FXUS64 KBRO 192319 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 619 PM CDT Tue Aug 19 2025 ...New AVIATION... .DISCUSSION... Issued at 133 PM CDT Tue Aug 19 2025 Rest of Today...Hot temperatures and daily chances of showers continue into this weekend. A MCS to our north this afternoon is working its way south- southwestward and, if it is able to sustain itself, can bring showers and thunderstorms to northern and western parts of the CWA. WPC has placed northern portions of Kenedy and Brooks counties in a Marginal Risk (level 1 of 4) of excessive rainfall, and rainfall rates up to 1-2" per hour are possible. Satellite- derived PWATs in coastal counties of 1.9-2" supports this (inland counties ranging from 1.6-1.8"). Hi-res guidance shows a large spread of how well this system will be able to maintain itself through the afternoon, but the primary timeframe for anticipated showers is this afternoon into later this evening - 9 PM or so. Despite uncertainty of coverage, I've bumped up PoPs to 40% in northern and western portions of the CWA this afternoon/evening. Along with the MCS, showers and thunderstorms along the sea breeze boundary have started to develop south of the Rio Grande River, and may continue to force further isolated showers and thunderstorms through the afternoon along and east of US 281/I-69C. Mesoscale interactions between outflow of the MCS and sea breeze are possible into this evening as the two intersect. Any showers and storms that form are capable of bringing briefly heavy rainfall leading to localized flooding and ponding, gusty winds 40 mph (up to 50 possible), and lightning. Wednesday onward...Diurnally driven rain chances with the sea breeze continue through midweek. As ridging over the Desert Southwest translates west, mid-level disturbances will provide instability and forcing to increase rain chances further. From Wednesday into the weekend, moderate rain chances across the CWA persist, however, details in precisely when and where scattered to isolated showers and thunderstorms will form are too mesoscale to pinpoint at this time. The greatest chances are late this week - Thursday to Friday - up to 60% in northern ranchlands, and 30-40% in the RGV. Thursday, Northern Zapata county is in a Marginal Risk of excessive rainfall (level 1 of 4). With increased rain chances comes increased cloud cover, at least for the latter half of the week. While muggy conditions have no intention of slowing down, lack of solar heating during the day will keep "Feels Like" temperatures in the afternoons a few degrees cooler than we've seen for the last couple weeks. Despite being below Heat Advisory criteria, it is imperative to continue practicing heat safety. For more information on heat safety, visit: weather.gov/heatsafety && .AVIATION... (00Z TAFS) Issued at 617 PM CDT Tue Aug 19 2025 VFR conditions are expected to generally prevail through the TAF period with easterly winds and another round of convection possible late Wednesday morning into Wednesday afternoon, especially near the sea breeze. && .MARINE... Issued at 1236 PM CDT Tue Aug 19 2025 A meek pressure gradient will allow for slight seas and gentle winds out of the south-southeast, becoming moderate in the afternoons and evenings with land-sea breeze. There is a chance of isolated to scattered showers and thunderstorms every day through the weekend, primarily Wednesday through Sunday. Conditions will be degraded in any storms over the waters, with gusty winds, lightning, and heavy rainfall. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 79 94 78 96 / 20 30 10 20 HARLINGEN 74 96 73 98 / 20 30 10 20 MCALLEN 78 99 77 101 / 20 4010 30 RIO GRANDE CITY 77 99 75 101 / 30 40 20 30 SOUTH PADRE ISLAND 80 88 80 88 / 20 20 10 10 BAYVIEW/PORT ISABEL 77 91 76 93 / 20 30 10 20 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...69-HK LONG TERM....69-HK AVIATION...56-Hallman