FXUS64 KHGX 202312 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 612 PM CDT Mon Jul 20 2026 ...New AVIATION... .KEY MESSAGES... - Hot conditions persist through the week with the hottest days Tuesday and Wednesday. - A Heat Advisory is in effect from 11 AM - 8 PM Tuesday. - NHC is monitoring the development of Tropical Depression Two, currently in the northeast Gulf. While forecast uncertainty remains fairly high, residents should monitor the latest forecasts and evolution of this system. - Corresponding rain and temperature forecasts for the local area are subject to changes later in the week and highly dependent on the tropics. && .DISCUSSION... Issued at 225 PM CDT Mon Jul 20 2026 Hot and humid conditions continue this afternoon as high pressure remains anchored over the region. Water vapor and visible satellite imagery depict a prevailing drier airmass and broad subsidence dominant across the area. Afternoon temperatures will climb into the mid 90s. When combined with sfc dewpoints in the 70s, heat indices will reach up to 107F, close to advisory levels. Be sure to practice heat safety if spending extended periods outdoors! The main weather story for the first half of the week continues to be the heat. A robust ridge of high pressure will remain anchored across the central and western CONUS, providing sufficient subsidence locally to keep highs on a steady upward trend. Some inland locations will likely see their first 100-degree day of the year by Tuesday or Wednesday. Simultaneously, low to mid-level moisture filtering inland from the Gulf will keep humidity levels elevated. The combination of hot and humid conditions will push peak heat index values into the 107 to 112F range Tuesday and Wednesday. A Heat Advisory has been issued for all of southeast Texas for Tuesday from 11 AM - 8 PM. Wednesday is shaping up to be even hotter (likely due to the approaching tropical system over the Gulf). Therefore, advisories will likely be extended in future forecast updates. Heading into Thursday - Saturday, attention turns toward the Gulf regarding the evolution of Tropical Depression (TD)Two. The mid to upper level ridge positioned to our northwest will serve as the primary steering focus, nudging the system on a general westward to west-northwestward track toward the northwestern Gulf. However, environmental factors including dry air entrainment and shear could influence the system's track and intensity. Please, see the Tropical discussion below for further details on this system and potential impacts for Southeast Texas. Forecast beyond Saturday remains sensitive to the final track and strength of TD Two. Well-above normal temperatures will be possible. Will continue to monitor for heat headlines through the weekend. JM && .AVIATION... (00Z TAF Issuance) Issued at 611 PM CDT Mon Jul 20 2026 VFR conditions and light winds will prevail. Winds will transition from the ssw this evening, to the wsw overnight into early afternoon, then back to the sw/ssw late in the day). There was some patchy fog around earlier this morning, but fcst soundings show a bit drier llvl conditions...so other than some rural locations mainly west of I-45, most terminals shouldn't see significant vsby drops. 47 && .MARINE... Issued at 225 PM CDT Mon Jul 20 2026 Surface high pressure will continue to bring light to occasionally moderate west to southwest winds and low seas across the Upper TX coast. Mariners should continue to monitor weather conditions, especially toward the end of the week as Tropical Depression Two moves westward along the northern Gulf. This system is forecast to strengthen into a tropical storm later today as it approaches southeast Louisiana, before weakening again into a tropical depression as it moves toward the Upper Texas coast Thursday and Friday. While forecast confidence remains low, given high uncertainty in track and intensity; significant impacts are not anticipated across our coastal waters. However, Small Craft Advisories could potentially be issued during this period with elevated winds and seas up to 6 ft (offshore). JM && .TROPICAL... Issued at 329 PM CDT Mon Jul 20 2026 As of 3 PM CDT, Tropical Depression Two continues to meander slowly northwestward in the northeastern Gulf. The system has become better organized relative to yesterday, featuring an increase in banding features as well as an uptick in deep convection near, though not completely collocated, with the center. Moderate upper-level shear and dry air continue to limit the rate of further organization. However, these conditions are not expected to prevent strengthening. Therefore, the depression is forecast to become a tropical storm later tonight or tomorrow as it continues its slow, northwestward drift. By Wednesday, a building ridge is expected to steer the system westward, placing it on a trajectory towards southeast Texas. The primary meteorological question for our area will be whether or not the system can survive the atmospheric and geographical hurdles that lie ahead of it. For starters, the system is expected to track near or over southern Louisiana, limiting its intensification due to land interaction. In addition, the building ridge will increasingly supply north to northeasterly wind shear. This would tend to decouple the mid-level circulation from the lower levels, weakening the system as it approaches southeast Texas. There's also the current entrainment of dry air, which coupled with the shear is resulting in an exposed center that is not collocated with the deep convection. Due to these environmental factors, the National Hurricane Center is predicting that the system will weaken back to a depression as it approaches southeast Texas towards the end of the week. That being said, we continue to strongly advise the public to monitor the forecast in case trends change. Self && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 72 98 78 100 / 0 0 0 0 Houston (IAH) 75 100 80 102 / 0 0 0 10 Galveston (GLS) 79 94 81 95 / 0 0 0 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Heat Advisory from 11 AM to 8 PM CDT Tuesday for TXZ163-164- 176>179-195>200-210>214-226-227-235>238-300-313-335>338- 436>439. GM...None. && $$ DISCUSSION...JM AVIATION...47 MARINE...JM