270 FXUS64 KBRO 042013 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 313 PM CDT Sun Aug 4 2019 ...The Heat Builds This Week as the Dog Days of August Intensify... .SHORT TERM (Tonight through Monday Night): Another hot summer day across the region out there with surface high pressure generally in control of our weather. Although the high is in control, sea breeze activity has yet again developed generally right along the I69E corridor from Cameron to Kenedy Counties. PWAT values in this area are between 1.5- 2" so a brief heavier shower or two is not impossible, but certainly the exception rather than the rule. Think this activity could get as far west of I69C but, CAMs or more specifically the ARW want to keep the better rain chances across the coastal counties for now. Blended HRRR/ARW with globals through the near term period. A warm/humid night is expected, but as stated high pressure is mostly in control so after diurnal heating think that overall rain chances drop significantly, especially the further inland you go. Monday looks very similar to today, however, a bit drier air may nose into the region. This will lead fewer showers/convection so decided to drop POPs for much of the inland areas. Did keep some mention in the coastal counties where there is a nonzero prob for precip. Beyond this there is very little change in the short term period. Synoptics are very similar to days prior with the dominant high pressure across the Desert Southwest. Hot conditions continue with mostly light winds through the forecast period. .LONG TERM (Tuesday through Sunday): The story continues to be the classic position and intensity of the "La Canicula" 500 mb ridge, which re-centers over southern/western New Mexico through Chihuahua state (Mexico) Tuesday...then eases into southwest Texas through Coahuila state Thursday. The ridge center then stretches east and southeast into south and central Texas...bringing even drier (and perhaps a touch hotter) air with it, including across the Rio Grande Valley. As the upper ridge stretches southeast, a slightly stronger surface high in the central/eastern Gulf will develop with it while the thermal trough ("heat low") intensifies a bit each afternoon/evening in the lee of the Sierra Madre. This will return the summer version of the Valley Wind Machine (moderate and gusty southeast winds by day and fresh evening/overnight breezes) beginning Wednesday and continuing through the weekend. Increasing sunshine and lowering dewpoints especially west of US 77 will bring even higher temperatures but allow humidity to fall a bit, which should keep heat index values in check in the 105 to 110 range most afternoon...hot but not to the point of heat advisory (111 or higher) issuances. Actual temperatures will continue to climb the ladder, likely peaking Thursday through Sunday with triple digits in all areas except mainly east of US 77. Upper 100s (107/108) are possible across the upper Valley and Rio Grande Plains during this time. For the beach, expect some level of upwelling to develop later in the week and into the weekend but intensity of the surf temperature drop remains to be seen. Either way, cooler waters against the hotter than average land should cut winds 10 to 20 mph (lower) at the beach than in the "wind machine" areas each day. One more issue to be aware of late this week is the potential for elevated fire danger across the Jim Hogg/Starr/Zapata and perhaps Brooks County area beginning as early as Thursday and becoming more pronounced Friday through the weekend. 20 foot winds should reach 15 to 20 mph with higher gusts all three days in these areas and there is a possibility for afternoon humidity to fall into the teens which could push values toward Red Flag Warning conditions. && .MARINE: (Today through Monday): Favorable marine conditions expected through the short term with generally less than 2 ft wave heights expected. Winds should also be generally less than 10 knots, which will limit overall wave heights. Can't rule out a stray shower or T'storm, however, this looks to be the exception rather than the rule. (Tuesday through Friday Night)...The gradually building gradient will increase overnight winds on the Gulf and afternoon winds on the Bay...with caution conditions (15 to 20 knots and gusty) likely arriving Wednesday and persisting through the end of the week. Seas in the Gulf will become moderate due to the nighttime winds (and initial daytime winds over pre-upwelled water) and winds could reach caution overnight across the Gulf beginning Wednesday night, dropping back with diurnal trends to 10 to 15 knots by day. Wavewatch is a bit slow to respond seas...so 4 feet could arrive a bit sooner than forecast but should occur at some point between Wednesday night and Friday. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 80 93 81 95 / 10 20 20 10 BROWNSVILLE 80 96 80 97 / 10 20 20 10 HARLINGEN 79 98 78 100 / 10 20 10 10 MCALLEN 80 100 81 102 / 10 20 10 10 RIO GRANDE CITY 79 102 80 103 / 10 10 10 10 SOUTH PADRE ISLAND 82 89 83 90 / 20 20 20 10 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV Short Term...55/RF Long Term...52/BSG Marine...55/52 Graphic Update/Addition...52/BSG