755 FXUS64 KBRO 211941 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 241 PM CDT Sat Aug 21 2021 .SHORT TERM (Tonight through Sunday Night): Spotty showers, with an occasional rumble of thunder, have developed since late morning over much of the area. These have been somewhat lesser in coverage than forecast, however, as any moisture surge from distant TC Grace has been largely suppressed to our south by a 592-dam high at 500mb anchored over south-central Texas. Hence, sunshine has allowed heat indices to climb into the 105-110F range once again, though this is certainly not unusual for mid-late August. Have downgraded the Coastal Flood Advisory to a Coastal Flood Statement valid until 7 PM CDT; see earlier AFD update for details. Elected to keep the High Surf Advisory (through at least 7 PM) and Rip Current Statement (through at least 7 AM Sunday) going, with nearby buoys reporting 10-12 second period swell and reports of strong rips near the South Padre Island Jetties this morning. Precip chances should end by early evening with the loss of daytime heating. Another warm, humid night is in store. Some guidance hinting at minor visibility reductions, to 4-6 miles, over interior portions of Hidalgo/Brooks/Jim Hogg counties, but confidence in this is pretty low at this time. High pressure aloft remains in control for Sunday, with high temperatures similar to today's readings, or perhaps a degree or two higher. Some mixing of drier air aloft should yield afternoon dewpoints ranging from the low-mid 60s over Zapata to the lower 70s in Brownsville. This would act to keep heat indices below Heat Advisory criterion (of 111F) again, though it will feel rather hot out in the sun. Little change for Sunday night, though model guidance (particularly the NAM) hints at a slight deepening of moisture over the southern coastal waters and lower RGV, which could lead to a nighttime shower or two, most likely after midnight. .LONG TERM (Monday through Saturday): A ridge of high pressure will continue to dominate over the region for start of the long term. While this will lead to subsidence across the region, weak perturbations on the southern side of the ridge will allow a slight chance of showers and thunderstorms to affect mainly coastal counties through Tuesday. As this ridge begins to break down on Wednesday, chances for precipitation increases across the CWA through Saturday, especially each afternoon. Forecast guidance shows PWATS under 2 inches so rain amounts should remain fairly light. Temperatures will remain seasonal through Tuesday but with the increase chances for showers/thunderstorms and cloud cover Wednesday through Saturday temperatures will likely remain just below normal but heat indices will still reach 103 to 110 most afternoons. && .MARINE(Now through Sunday Night): Swells originating from then Hurricane Grace's trek across the Bay of Campeche still keeping seas stubbornly hazardous on the Gulf waters, with the Small Craft Advisory in effect until 1 AM Sunday. Latest report from Buoy 42020, as of 1840 UTC/1:40 PM CDT, is 7 ft. swells (8 ft. combined seas) with a dominant period of 11 sec. TABS-K, further south, is at 10 ft. seas with similar period. Seas should gradually subside to sub-hazardous levels by the pre-dawn hours of Sunday, with improving trend continuing through Sunday night with moderate SE winds and seas down to ~4 ft. by 1200 UTC Monday due to modest surface high pressure taking control over the Gulf. Monday through Thursday...Generally favorable marine conditions are expected to prevail as the swell from Grace subsides through the period. Winds will remain light to moderate out of the east or southeast and wave heights will be around 2 to 4 feet on the Gulf. Showers and thunderstorms are possible through the period that could lead to localized increased winds and elevated seas. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 78 92 78 92 / 10 10 20 20 BROWNSVILLE 79 96 79 95 / 10 10 20 20 HARLINGEN 76 96 77 95 / 10 10 10 10 MCALLEN 76 98 76 98 / 0 10 0 10 RIO GRANDE CITY 76 101 75 101 / 10 10 0 10 SOUTH PADRE ISLAND 83 88 82 89 / 10 10 20 20 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Sunday morning for TXZ256-257-351. High Surf Advisory until 7 PM CDT this evening for TXZ256-257- 351. GM...Small Craft Advisory until 1 AM CDT Sunday for GMZ150-155-170- 175. && $$ This product is also available on the web at: https://weather.gov/rgv 53-Schroeder/Short Term 68-McGinnis/Long Term