FXUS64 KHGX 171030 CCA AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 530 AM CDT Wed Jun 17 2026 ...New AVIATION... .KEY MESSAGES... - Tropical Storm Watches remain in effect along portions of the Upper Texas Coast with Tropical Storm Warnings in effect for portions of the Gulf waters. - Heavy rainfall amounts of 2-4" with localized higher totals may lead to additional flash flooding through early this evening across southern and coastal portions of the forecast area. - Coastal flooding remains possible through Wednesday evening, with greatest potential around times of high tide overnight tonight through early Wednesday morning. - Hazardous heat will build across southeast Texas late this week into early next week. Those planning outdoor activities should prepare for dangerous heat indices. && .DISCUSSION... Issued at 127 AM CDT Wed Jun 17 2026 Satellite imagery shows the center associated with Potential Tropical Cyclone 1 emerging over the northwestern Gulf early this morning. Most convective bands remain displaced to the east and northeast of the center given the effects of shear over the tropical disturbance. This system is forecast to lift northeastward along the Texas coast and adjacent northwestern Gulf through Wednesday afternoon before eventually tracking toward the vicinity of the Texas/Louisiana border by Wednesday evening. Heavy rainfall and a potential for flash flooding will remain the primary impact of concern over portions of southeast Texas, especially near and along the coast where additional widespread rainfall amounts of 2-4 inches with localized totals in excess of 5+ inches will remain possible. More information on the hydrologic situation is included in an additional section below. Coastal flooding will also impact the immediate coast through Wednesday evening as onshore flow strengthens ahead of the approaching system. A Coastal Flood Warning remains in effect for Bolivar Peninsula, with a Coastal Flood Advisory from Galveston Island to the Brazoria and Matagorda Islands. The best potential for coastal flooding will be from late tonight into Wednesday morning/early Wednesday afternoon around times of high tide. No changes were made to Tropical Watches/ Warnings as of the 10 PM NHC Advisory. Tropical Storm Warnings remain in effect from the Coastal Waters from High Island to Freeport TX out 20 NM and waters from Freeport to Matagorda Ship Channel 20-60 nm out and from High Island to Freeport TX 20-60 nm out where confidence of winds up to 35 kt with gusts potentially over 40 kt was highest. A Tropical Storm Watch remains in effect for Galveston Bay as well as Galveston Island, Coastal Galveston County, Bolivar Peninsula, Chambers, Coastal Brazoria, and the Brazoria Islands where tropical storm force conditions may be briefly possible through late Wednesday. A very low tornado threat remains highlighted along the immediate coast through Wednesday with a Marginal Risk from SPC. Rain chances will quickly end from west to east this evening/tonight as the system lifts northeast away from our region. Focus will then shift toward building heat through the latter part of the week and into the weekend and early next week as temperatures warm back into the lower to mid 90s F (32-36 degrees C) with very high humidity contributing to heat index (feels like) temperatures reaching into the 105-112 degrees F (41 to 44 degrees C) range Thursday through early next week. While we are not expecting to meet Heat Advisory criteria today, there could be heat index readings as high as 100-106 F (38 to 41 degrees C) this afternoon. Hazardous heat products will likely become needed as early as Thursday. Those planning outdoor activities should be prepared for the heat and high humidity. Remember to stay hydrated (water or beverages with electrolytes), take frequent breaks in the shade or a cool place, and limit strenuous activities if planning to spend time outdoors. Isolated to scattered afternoon and evening showers and thunderstorms will be possible each day Thursday-Saturday but a building ridge may further limit convective development late this weekend into early next week. && .AVIATION... (12Z TAF Issuance) Issued at 530 AM CDT Wed Jun 17 2026 Moderate to heavy rain is spreading onshore this morning with the heaviest rain affecting HOU and GLS this morning with IFR conditions. Elsewhere, showers will spread inland with MVFR to IFR ceilings this morning. Later today, as the low pressure in the Gulf moves away from the area, rain and showers will taper off. IFR ceilings are expected to improve to MVFR to VFR. Winds will stay gusty along the coast at GLL through the day with decreasing winds at IAH and HOU this afternoon. && .MARINE... Issued at 127 AM CDT Wed Jun 17 2026 Numerous to widespread showers and thunderstorms will continue to develop over the marine area tonight into Wednesday as Potential Tropical Cyclone 1 approaches. A few waterspouts will remain possible. Onshore winds increase overnight into Wednesday morning as the system moves into the marine area, followed by moderate to strong westerly flow behind the departing system Wednesday afternoon and evening. Seas build to 6-11 feet tonight into Wednesday ahead of the approaching tropical system and remain elevated through Wednesday and remain elevated between 5-8 feet Wednesday night into Thursday. Seas still look to drop to below 6 feet by Friday. && .HYDROLOGY... Issued at 127 AM CDT Wed Jun 17 2026 Pockets of 4-6+" of rainfall occurred across portions of Southeast Texas on Tuesday, most notably over northwestern Harris County into southern Montgomery County where widespread street flooding was observed. This rainfall along with rainfall from previous days has left the grounds fairly saturated. This would allow for a quicker transition of additional rainfall to runoff. This increases the potential for street flooding, especially along the coast where the rainfall threat persists through this afternoon as PTC One skirts along the Upper Texas coastline. Latest high-resolution model guidance still reflects a tight rainfall gradient with the highest totals remaining closer to the coast. As a result, the Flood Watch has been trimmed down to include mostly counties along and south of I-10. One exception is Montgomery County...keeping them in the Flood Watch for now since the very saturated soils leaves the southern portion of the county vulnerable to additional rounds of flooding if they were to receive even less than an inch of rainfall this morning. Additional widespread totals of 2-4" with isolated higher amounts are anticipated with the highest totals along the coast. The end time of the Flood Watch has also been trimmed to now end on Wednesday afternoon as the forecast for Thursday has trended drier in the wake of PTC One. Be sure to remain weather aware and have multiple ways to receive alerts. A few river gauges remain in minor flood stage early this morning: Menard Creek at Rye (RYET2), San Bernard River at Boling (BOLT2), and Tres Palacios River at Midfield (MTPT2). The San Bernard River at Sweeny (OCNT2) is currently cresting just below minor flood stage. Remember that you can monitor updated river forecasts via the NWS NWPS webpage (https://water.noaa.gov/). Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 89 77 94 80 / 10 0 0 0 Houston (IAH) 88 78 94 81 / 50 10 10 0 Galveston (GLS) 88 84 90 84 / 80 30 20 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Tropical Storm Watch for TXZ214-337-338-437>439. Flood Watch from this evening through Thursday morning for TXZ164-177>179-197-198-210>212. Flood Watch through Thursday morning for TXZ199-200-213-214-226- 227-235>238-300-313-335>338-436>439. Coastal Flood Advisory until 7 PM CDT this evening for TXZ436>438. Coastal Flood Warning until 7 PM CDT this evening for TXZ439. GM...Small Craft Advisory until 9 AM CDT Thursday for GMZ330. Tropical Storm Watch for GMZ335-350. Tropical Storm Warning for GMZ355-370-375. && $$ DISCUSSION...CLL AVIATION...WFO TAE MARINE...CLL