Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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963 FXUS64 KBRO 221917 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 217 PM CDT Sun Sep 22 2024 ...New SHORT TERM, LONG TERM, MARINE... .SHORT TERM... (Tonight through Monday night) Issued at 214 PM CDT Sun Sep 22 2024 Mid-level ridge continues to a major player in the short term forecast for Deep South Texas and the Rio Grande Valley through the short term forecast period. As the ridge will start to drift off towards the east more by Monday, a weak mid-level trough will start to move into the eastern part of Texas. With daytime heating and a small increase in PWAT values, there is a slightly greater chance for isolated showers and thunderstorms to occur over the eastern most counties along with the sea breeze during the afternoon tomorrow. As for the temperatures, highs are expect to be generally in the low to mid 90s. The heat indices are expected to be around 105, which is below the criteria for a Special Weather Statement for elevated heat indices and Heat Advisory. The low temperatures are expected to be in the 70s. && .LONG TERM... (Tuesday through next Sunday) Issued at 214 PM CDT Sun Sep 22 2024 Deep mid-level troughing over the North Central Plains, the right (east) side of an omega block over the Western CONUS, will stand in counterpoint to modest, east to west elongated ridging over the Gulf and South Texas at the beginning of the long term (Tue). A tropical system will concurrently be taking shape over the NW Caribbean (see the marine discussion below for more detail). Deep South Texas and the Gulf of Mexico will see mainly seasonal but nonetheless somewhat unsettled weather during the initial phase of the long term. Convection over the Gulf of Mexico will be a staple, but daytime sea breezes will feed off ample available moisture and will spread over the CWA with isolated to scattered showers and tstorms Tuesday through Wednesday and early Thursday. Efficient precipitation processes may result at times in brief heavy rainfall, with the threat of mainly isolated, nuisance type flooding. We forecast modest accumulation below flash flood guidance through Thursday. The mid-level low will drop south into the Southern High Plains by Wednesday and Thursday, pulling drier air across West Texas toward the lower RGV behind a cool front. The front may be strong enough to push through the CWA to the Gulf Thursday afternoon, all but ending any significant rain chances for the remainder of the long term. Meanwhile, the mid-level low itself and the northward moving tropical system appear to do a dance with each other Friday and Saturday, interacting and somehow combining over the lower to mid Mississippi Valley. That scenario leaves deep South Texas more or less out of the main action and takes us to the end of the current long term. Through the early long term, temperatures will trend slightly above normal with a good mix of clouds and sun and light to moderate winds. High temps will be mainly in the lower to mid 90s with lows in the lower to mid 70s. By Wednesday (the best day for rain) east to southeast winds will start to back to north and northeast as they will be influenced by low pressure to the north instead of Gulf high pressure. Some drying will occur on Thursday, followed by fewer clouds next Friday through Sunday as the drying continues. Overnight low temps starting Thursday night will trend down slightly - toward more normal values due to the drier air. Rip current risk may increase mid to late week as larger, longer period swells make their way west across the Gulf toward the lower Texas coast. && .AVIATION... (18Z TAFS) Issued at 1244 PM CDT Sun Sep 22 2024 VFR conditions are expected to continue through the TAF cycle at all TAF sites. Skies are expected to range between mostly sunny to partly cloudy. Light easterly to southeasterly winds are expected to persist through the TAF cycle as well. While some showers and thunderstorms could develop with the sea breeze during the afternoon hours, confidence was not high enough to include in the TAF package. && .MARINE... Issued at 214 PM CDT Sun Sep 22 2024 Tonight through Monday Night...Favorable marine conditions are expected to persist through Monday night. Light to moderate onshore flow and low to moderate seas will continue through the period. Isolated showers and thunderstorms are possible and could result in locally elevated winds and seas. Tuesday through Friday night...we expect light to moderate east to southeast winds and low to moderate seas through Tuesday night. East to southeast winds will back to north and northeast on Wednesday and will subsequently become moderate to fresh over the Gulf of Mexico waters on Thursday. Small craft should exercise caution to low end small craft advisory conditions will be possible on Thursday through Friday night on the Gulf, mainly from building seas. Isolated to scattered showers and thunderstorms will develop from time to time through Thursday or Thursday night. A broad area of low pressure is over the NW Caribbean Sea and adjacent parts of Central America. Environmental conditions appear favorable for gradual development of this system during the next several days. A tropical depression will likely form while the system moves slowly north across the northwestern Caribbean Sea and Gulf of Mexico through the end of the week. There is a high chance (80%) of tropical cyclone formation in the next seven days. Regardless of development, winds and seas will start increasing across the SE Gulf early this week. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 77 91 77 90 / 0 30 30 60 HARLINGEN 74 92 74 92 / 0 30 10 60 MCALLEN 77 96 77 96 / 10 20 10 40 RIO GRANDE CITY 75 95 74 94 / 0 10 10 30 SOUTH PADRE ISLAND 81 88 80 87 / 10 30 40 50 BAYVIEW/PORT ISABEL 77 89 77 89 / 0 30 20 50 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...64-Katz LONG TERM....54-BHM AVIATION...64-Katz