FXUS64 KHGX 271852 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 152 PM CDT Sun Sep 27 2026 ...New DISCUSSION, AVIATION, MARINE... .KEY MESSAGES... - Pattern change will occur mid-week this week, with increasing potential for showers and thunderstorms - Slight risk of excessive rainfall for portions of SE Texas on Wednesday and all of SE Texas on Thursday && .DISCUSSION... Issued at 1230 PM CDT Sun Sep 27 2026 The axis of the mid-upper level ridge will continue to shift east during the Monday, as remnants of Polo merge with an amplified trough moving in from the California area. Over the next couple of days a series of weak impulses aloft will move through and interact with the warm air advection from the Gulf, resulting in isolated showers and storms along the coast and Gulf Waters Monday and Tuesday. The aforementioned trough will slow down upon arrival into Texas, by which point the remnants of Polo are expected to have become engulfed within the overall flow. Polo's remnants will bring an extra surge of tropical moisture into the region as it merges with the trough. At the same time, southeasterly flow in the lower levels will pull in moisture from the Gulf. As a result, PWAT values will increase into the 2.3-2.5" range (>99th percentile for this time of year). The amount of rainfall southeast Texas will experience will depend heavily on: 1) Where the trough axis sets up 2) How much the trough slows down once it arrives in Texas Right now it looks like a battle between pressure systems...to start, as the trough arrives in Texas, a second area of low pressure looks to develop over the Gulf of America, impacting the flow of the westernmost trough (slowing the progression). By Thursday, high pressure off the east CONUS expands over the Southeastern CONUS, pushing the low pressure in the Gulf southward and pushing against the trough over Texas (continuing to slow the progression). Models begin to diverge on what happens Thursday through the weekend. GFS remains more progressive and the trough becomes absorbed into what is currently TD 18-E in the Pacific. ECMWF remains the slower solution and keeps the Pacific tropical system offshore, allowing the trough over Texas to hang around through most of the weekend. So what does this mean for Southeast Texas? Right now we are seeing increasing potential for showers and thunderstorms for the latter half of the week, with heavy rainfall potential also increasing. Ensemble guidance has consistently shown 99th percentile range for moisture. Probabilistic guidance has been steadily increasing the chance of most of the area seeing at least an inch of rainfall (60-80% chance this forecast period) and there has been a slight uptick in the chance of some locations within the overall area seeing greater than 2" of rainfall (30-45%). The thing we will want to keep an eye on over the next couple of days is how the trough evolves, where the axis sets up, and if the aforementioned pressure systems over the eastern CONUS/Gulf strengthen or weaken. If the axis shifts more east than what is currently forecast and the system slows down/stalls, that would certainly increase the QPF for southeast Texas, as well as the potential for flash flooding. Currently, WPC has most of the area in a slight risk for excessive rainfall for Wednesday, and for the entire area on Thursday. QPF for Wednesday through the weekend is around 3-5". I would like to point out, again, to not focus on exact amounts, and instead on potential impacts. This forecast continues to evolve, and will likely continue to evolve over the coming days, especially when Hi-Res guidance comes in. As far as temperatures are concerned, highs will be in the 90s for a few more days, with rainfall expected to bring highs down into the 80s during the latter part of the week. Lows will be in the 70s through the week. A frontal boundary is projected to move through the area during the day Saturday, bringing drier air and slightly cooler temperatures. Highs Saturday and Sunday are forecast to be in the low to mid 80s. Bailey && .AVIATION... (18Z TAF Issuance) Issued at 1230 PM CDT Sun Sep 27 2026 VFR conditions persist for the entire forecast period. Any popcorn convection or showers are anticipated to remain confined to the east of GLS and off shore. The light SE continues before relaxing overnight. Low-lying areas around CXO have the chance around sunrise for BR to develop and briefly reduce VIS to MVFR. This clears as winds pick back up, once again, out the SE. The main difference for tomorrow will be the increased winds and gusts periodically in the afternoon/evening. CMW && .MARINE... Issued at 1230 PM CDT Sun Sep 27 2026 Light east to southeast winds and low seas will prevail today. Unsettled weather is expected as early as Tuesday and continuing through the weekend. This will be the result of a disturbance moving through the Plains and ejecting a frontal boundary into Southeast Texas. Periods of showers and thunderstorms will peak Thursday and Friday, with elevated winds and building seas up to 8 feet. Small Craft Advisories will likely be in effect after midweek Bailey && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 97 73 96 72 / 0 0 0 0 Houston (IAH) 94 76 94 76 / 10 0 10 0 Galveston (GLS) 88 82 88 82 / 20 0 20 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...Bailey AVIATION...CMW MARINE...Bailey