FXUS64 KBRO 091823 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 123 PM CDT Thu Jul 9 2026 ...New DISCUSSION, MARINE... .KEY MESSAGES... Updated at 105 PM CDT Thu Jul 9 2026 - Low (15-30%) chances of rain this afternoon and late tonight increase to a low to medium (30-60%) chance by tomorrow afternoon from possible rounds of showers and thunderstorms. - High moisture content could result in heavy rain into tomorrow and a few areas may receive up to an inch or more, most likely along/east of US-281/I-69 E. - Afternoon heat indices of around 100-105 F and minor heat risks (level 1 of 4) this afternoon warm and escalate to 105-110 F with a mostly moderate heat risk (level 2 of 4) tomorrow into the middle of next week. - A medium risk of rip currents continues through tomorrow afternoon. && .DISCUSSION... Issued at 105 PM CDT Thu Jul 9 2026 The combination of weak troughing aloft over northeastern Mexico and an influx of deep and tropical moisture via southeasterly winds, gusting to 20-25 mph, bring the potential for several rounds of isolated to scattered, possibly numerous, showers and thunderstorms today into tomorrow. Due to the disorganized nature of convection from weak forcing, forecast confidence over the next 24-48 hours is medium at best and is likely to change. However, our latest forecast holds a low (15-30%) chance of rain along the seabreeze boundary moving from the Lower to Middle RGV throughout this afternoon and early evening hours from the initial onslaught of significantly enhanced moisture currently developing showers and thunderstorms just offshore. As PWAT values of 2.0+ in. spread to most of deep south Texas tonight through tomorrow night, a low to medium (20-40%) chance of rain late tonight along/east of I-69 E increases to a low to medium (30-60%) chance and expands westward to the I-69 C/US-281 corridor by tomorrow afternoon, with the higher chances over eastern portions of the Northern Ranchlands. Given such high moisture content, there exists the potential for heavy rain. By Saturday morning, we expect nearly half of locations along/east of US-281 to receive at least 0.20-0.30 of an inch of rain by Saturday morning, most concentrated across along/near the coast as well as portions of the Middle RGV, where we anticipate generally between a half inch to an inch of rainfall. Despite the potential for extended periods of cloud cover reducing diurnal instability just a bit, heavy rain developing or training could lead to isolated 1-3+ inches, most likely within the areas mentioned, especially late tonight into tomorrow afternoon when PWAT values could peak as high as 2.75 in. Global models are in agreement that the westward expansion of a high pressure aloft over the Gulf is likely to cut down on chances of rain on Saturday, with a low (15-30%) chance along the afternoon seabreeze across the Northern Ranchlands, decreasing to a 15-20% chance on Sunday and Monday afternoons. Yet, pulses of deep moist air streaming in off the Gulf could still result in more isolated pockets of heavy rain. Another area of weak upper level troughing could return a low chance (15-30%) of showers and thunderstorms along the afternoon seabreeze by the middle to later parts of next week. Increasing cloud cover holds high temperatures in the low/mid 90s today and tomorrow. Meanwhile, increasing moisture content warms and escalates afternoon heat indices from around 100-105 F with a minor heat risk today to near 105-110 F with mainly or all moderate heat risks tomorrow into next Tuesday. Following, drier air and increasing cloud cover may result in minor to moderate heat risks as afternoon indices peak close to 100-110 F. && .AVIATION... (18Z TAFS) Issued at 1222 PM CDT Thu Jul 9 2026 An area of convection just offshore the Lower Texas coast has resulted in VCTS reported at KBRO at this time, though the closest detected lightning has been around 45+ SM to the east. PROB30s have been introduced to the 18Z TAF cycle as the moisture over the Gulf begins to work its way inland via the seabreeze boundary; ongoing cloud cover could result in VCSH for KBRO and KHRL later this afternoon and into the early evening hours, yet abundant sunshine and enhanced inland instability may lead to VCTS at KMFE. Chances of rain decrease into the later evening and early night hours tonight before increasing back to a low chance late tonight and into tomorrow afternoon for KBRO and KHRL as showers and thunderstorms develop. Southeasterly winds of around 10-15 knots, with gusts up to around 20-25 knots this afternoon decrease back to gentle tonight into midday tomorrow as VFR conditions prevail, though brief periods of reduced instability are possible from potential heavy rain within showers and thunderstorms that develop. && .MARINE... Issued at 105 PM CDT Thu Jul 9 2026 Gentle to moderate southeasterly winds and slight to moderate (2-5 ft) seas continue through the next 7 days along with potential brief periods of Small Craft Exercise Caution headlines. Chances of rain incise to as much as a low to medium (20-50%) tonight through tomorrow afternoon as rounds of showers and thunderstorms continue. Low (15-30%) chances of rain follow tomorrow night into next Monday and may return by the middle of next week. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 78 92 81 94 / 40 40 10 10 HARLINGEN 75 93 78 95 / 30 40 10 20 MCALLEN 78 96 81 98 / 10 30 10 10 RIO GRANDE CITY 76 96 79 99 / 10 20 10 20 SOUTH PADRE ISLAND 80 87 82 88 / 50 40 20 10 BAYVIEW/PORT ISABEL 77 90 80 92 / 40 40 20 10 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...65-Irish LONG TERM....65-Irish AVIATION...65-Irish