Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
944 FXUS64 KHGX 190524 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1224 AM CDT Tue Aug 19 2025 ...New KEY MESSAGES, DISCUSSION, MARINE... .KEY MESSAGES... Issued at 1222 AM CDT Tue Aug 19 2025 - Isolated to scattered showers and storms overnight will continue to develop across portions of Southeast TX through the day. A few storms will be capable of producing gusty winds and locally heavy rain. - Hot and humid conditions remain with a daily risk of showers and thunderstorms. - There is potential for locally heavy rainfall after midweek with a marginal risk for excessive rainfall for multiple days. && .DISCUSSION... Issued at 1222 AM CDT Tue Aug 19 2025 The region remains under the influence of a weak sfc ridging. However, the main 500 mb high ridge that has been a fixture over the area will continue to shift further westward across the SW CONUS today. This westward shift will allow for deepening troughiness in our area, providing a more favorable environment for lift and precipitation. Therefore, a passage of a series of shortwave troughs can be expected today and Wednesday. Per IR satellite imagery and radar, the first of these shortwaves is currently moving across Liberty and Chambers counties. As these storms move into our more stable environment (lapse rates around 6 C/kg or less), they are expected to be less likely to remain strong overnight. The situation could be a bit different after daybreak. With the combination of mid to upper-level forcing from the shortwave, daytime heating, and ample moisture (PWs nearing 2.1 inches), thunderstorm activity is expected to increase in intensity and coverage through the day. The best chances for rain/storms will be after sunrise, with the highest probability for areas along and south of I-10 after mid-late morning. A similar scenario is anticipated on Wednesday as the parade of mid-level shortwaves continues. A few strong storms will be possible today and Wednesday with gusty winds and brief heavy rain as the primary hazards. A pattern change is expected with the arrival of a weak/slow-moving cold front. A cold front in August generally brings less hot conditions and rain/storm chances. This is what we can expect on Thursday and Friday. Models continue to bring an uptick in moisture along the surface convergence boundary with precipitable water values at or above 2.0 inches, leading to increasing rain and storm chances. In fact, a few of these cells could produce pockets of heavy rainfall, resulting in minor street flooding. Confidence in exact rainfall totals and the location of the heaviest rain is still moderate. For now, expected increasing rain/storm chances Wednesday into Friday along and ahead of the boundary. WPC placed our region under a Marginal Risk of excessive rainfall for Wednesday through Friday. The front washes out and/or becomes stationary along the coast during the weekend. Therefore, will continue with daily rain and storm chances, with the best probabilities in the afternoon. In terms of temperatures, the heat continues. Despite increasing troughiness aloft, 850 mb temperatures show values into the 19 to 23 degC range, suggesting surface highs in the mid to upper 90s each day. Given increasing rain and storm chances with the FROPA, highs could potentially be in the low to mid 90s Thursday and Friday. Confidence is low to moderate, as it will depend on the time of arrival of the front. The main key points here are that the heat continues and combined with increased humidity levels, heat indices could reach the 105 to 107F in some areas. Don`t forget to practice heat safety! JM && .AVIATION... (00Z TAF Issuance) Issued at 606 PM CDT Mon Aug 18 2025 Afternoon showers/storms should taper off this evening. VFR conditions largely dominate throughout the night, though isolated patchy fog could develop during the early morning hours of Tuesday. During this period, another round of showers could push across the region (northeast to southwest). If these showers/storms are strong/widespread enough, then it could stabilize conditions, leading to lower rain chances that afternoon. If not, then we`ll probably see more activity during the afternoon hours. Otherwise VFR conditions prevail with light N/NE winds shifting E/SE throughout the day. 03 && .MARINE... Issued at 1222 AM CDT Tue Aug 19 2025 Generally, light winds and low seas will persist through most of the work-week along with daily rain and storm chances. The effect of landbreeze and seabreeze will continue to bring offshore winds late night into early mornings, before gradually shifting onshore in the afternoon and evening. A weak summer cold front will attempt to move through the coastal waters Thursday into Friday. Scattered rain/storms and a brief period of offshore winds expected with the FROPA. Gusty winds and brief reduced visibility can be expected near/around any strong storms. JM && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 76 98 75 94 / 10 50 40 70 Houston (IAH) 79 97 78 94 / 10 60 40 70 Galveston (GLS) 82 93 81 92 / 20 40 40 60 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...JM AVIATION...03 MARINE...JM