Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
790 FXUS64 KHGX 181726 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1226 PM CDT Mon Aug 18 2025 ...New AVIATION... .KEY MESSAGES... Issued at 1155 AM CDT Mon Aug 18 2025 - Hot and humid conditions through midweek with heat indices near advisory criteria at times...be sure to practice heat safety! - Daily chances for showers and storms continue throughout the week with increased rain chances after midweek. - There is potential for locally heavy rainfall after midweek with a marginal risk for excessive rainfall for multiple days. && .DISCUSSION... Issued at 1155 AM CDT Mon Aug 18 2025 It`s very fitting that today is National Fajita Day since we`re feeling the sizzle from the mid-August heat. I think these temperatures would be A LOT more bearable if it came with sides of tortillas, guacamole, and cheese. If you walk outside you can just feel how steamy it is with high temperatures topping out mostly in the upper 90s. The humidity adds some extra spice to the grill (yeah I`m still thinking about those fajitas), which leads to heat indices well into the triple digits. Dew points mixing out into the low 70s later this afternoon should prevent widespread advisory-level heat indices (108+F). Now there will be some locations that will see heat indices at or above 108F this afternoon. However, since these values are not expected to be that widespread or occur for an extended period of time, a Heat Advisory is not in effect. Regardless of that though, you should still practice heat safety especially if you`ll be outdoors for an extended period of time. There will be opportunities for a brief cooldown due to isolated to scattered showers and storms this afternoon. Rain chances are higher today as the mid-level high is gradually nudging northwestward, which places us in position to get passing shortwaves moving in from the northeast. Speaking of shortwaves, a rather robust one looks to move in early Tuesday morning...the timing of it isn`t the best but it could still lead to a cluster of showers/storms. If those manage to develop we`ll need to monitor gusty winds if any of those storms manages to become strong. 500mb heights will be on a gradual decreasing trend going into midweek as the mid-level high retreats northwestward, but with 850mb temperatures remaining near or above the 90th percentile we`ll still manage to squeeze out high temperatures in the mid to upper 90s. Heat indices will still reach into the triple digits and flirt with the advisory threshold in some locations. After midweek is when things become a bit more interesting...a summer cold front?! Now don`t get too excited and go looking in the back of your closet for jackets, it`s still August! Since the center of the mid-level high will be over the Four Corners region, a trough will be able to slide down into the southern/southeastern CONUS with an associated frontal boundary. Moisture convergence along the boundary will lead to PW values surging above the 90th percentile towards the end of the work week. There will be multiple factors at play here in terms of how much rain we see and exactly where the rain will fall each day, but just know that rain chances increase towards end of the work week. Additionally, some of that rainfall could be locally heavy. Areas north of I-10 are already outlined in a marginal risk (level 1 out of 4) of excessive rainfall on Wednesday...and that expands to all of Southeast Texas on Thursday and Friday. Daily shower/storm chances stick around going into the weekend. As a result of the increasing rain chances, temperatures will be on a decreasing trend after midweek. We`ll trade out the highs in the mid to upper 90s for highs in the low to mid 90s towards the end of the work week. Until then though, it`s gonna be hot, so be sure to continue to practice heat safety especially if you`ll be outdoors for an extended period of time: know the signs of heat- related illnesses, stay hydrated, take frequent breaks from the heat, wear sunscreen, and ALWAYS LOOK before you LOCK your vehicle. Don`t forget about your pets as well! If the ground is too hot for the palm of your hand, then it is too hot for their paws. Batiste && .AVIATION... (18Z TAF Issuance) Issued at 1225 PM CDT Mon Aug 18 2025 VFR and generally light and somewhat variable winds (more onshore than other directions today, more NEerly than other directions tomorrow) put focus on SHRA/TSRA potential. Keep PROB30s at most sites this afternoon, but guidance is really gung ho on TSRA around Houston metro between 21Z and 01Z, with suite of short range models suggesting a peak of 70 percent TSRA probability over Harris County at 23Z. Have stepped the metro terminals up to TEMPO to reflect that. Tonight, a quick and weak disturbance will bring another chance for SHRA or maybe even a stroke of lightning or two, so another round of PROB30 -SHRA from 10-14Z or so. With the subtle change in winds for tomorrow, am holding off on any mention of SHRA/TSRA tomorrow afternoon, as that round may be a bit subdued. && .MARINE... Issued at 1155 AM CDT Mon Aug 18 2025 Light winds and low seas will prevail throughout the forecast period, but the wind direction will fluctuate due to the landbreeze/seabreeze daily. Expect offshore winds during the late night to morning hours becoming onshore in the afternoon to evening hours. Daily chances for showers and storms will persist throughout the week with rain chances increasing after midweek. Winds and seas could be locally higher in and near any of the stronger storms. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 76 98 76 98 / 10 50 10 50 Houston (IAH) 79 97 79 97 / 40 70 10 50 Galveston (GLS) 82 92 82 93 / 50 70 20 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...Batiste AVIATION...Luchs MARINE...Batiste