Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
556 FXUS64 KHGX 200535 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1235 AM CDT Wed Aug 20 2025 ...New DISCUSSION, MARINE... .KEY MESSAGES... Issued at 1228 AM CDT Wed Aug 20 2025 - Hot and humid conditions continue today with scattered to isolated storms. - A weak boundary approaching from the north should increase shower/storm coverage on Thursday & Friday with locally heavy rainfall possible. - Rain chances lower over the weekend, but we should continue to see some diurnal storms into next week, especially near the coast during the afternoon. && .DISCUSSION... Issued at 1228 AM CDT Wed Aug 20 2025 Today will see a similar pattern weather-wise as we remain on the southeastern edge of a mid/upper level ridge. Additional shortwave impulses will round the peripheral of the ridge to pass over SE Texas from the north, which should tap into the abundant moisture to produce some showers/thunderstorms. CAM guidance has faced difficulty with depicting convection these last few days, though the broad consensus between models puts greater storm coverage & rain chances around/north of the I-10 corridor. Should see much of this activity during the afternoon period, coinciding with daytime heating, though again take all this with a grain of salt, as it seems the 00z CAMs have done a poor job initializing activity upstream in Oklahoma. This environment still features high precipitation efficiency, thus there is a chance that a few storms could produce some stronger downpours with locally heavy rainfall. Thursday and Friday sees a more noticeable pattern change with the introduction of a weak boundary, which should push into SE Texas on Thursday and eventually stall out near the coast (though I wouldn`t get very attached to an exact timing right now based the shaky CAM performance). Pooling moisture, the influx of additional lift provided from the boundary and shortwave impulses moving over the areas should enable greater coverage for showers/thunderstorms through Friday. High precipitation efficiency will still enable storms to produce strong downpours and possibly locally heavy rainfall on these days especially. WPC currently has SE Texas under a Marginal (level 1/4) Risk of Excessive rainfall on Thursday. The 00z CAMs seem rather sparse with convection for Thursday, though again I`d be skeptical to take this as truth this far our given the current runs struggles to capture ongoing activity. Friday isn`t outlooked yet, but reasonably could see a Marginal risk as well depending on how the mesoscale environment evolves, though the moisture axis should generally fall south of the I-10 corridor by this point. Ridging is poised to strengthen over the Desert Southwest this weekend, which should broadly reduce PoPs (with the main moisture axis shifting further offshore) and pull up temperatures once again. However, daily chances for showers/storms should continue into next week, especially as a broad upper level low/trough over the Great Lakes/Quebec/Ontario is poised to push another frontal boundary & round of shortwaves towards our area early next week. Greater model spread emerges at this point of the forecast, though the broad strokes remain the same as predominantly hot weather with daily thunderstorm chances persist. 03 && .AVIATION... (00Z TAF Issuance) Issued at 626 PM CDT Tue Aug 19 2025 Showers with a few thunderstorms will continue to move/weaken southwest, away from terminals early this evening. Then, a tranquil night is expected with mostly clear skies, before another round of showers and storms arrives on Wednesday. This activity is expected to develop from north to south during the day, with the best chances after midday. Gusty/erratic winds, small hail and reduced visibility due to localized heavy rain are possible with the strongest storms. Overall, light and variable winds will prevail through most of the period. Patchy fog, mostly low-lying fog cannot be ruled out around CXO and SGR terminals by early Wednesday morning. JM && .MARINE... Issued at 1228 AM CDT Wed Aug 20 2025 Conditions will be fairly calm with 1-3 ft seas and seabreeze- landbreeze driven winds around 5-10 knots (offshore/northwesterly early in the morning, then onshore/southeasterly in the afternoon). Isolated to scattered showers and storms will be a daily possibility, primarily during the daytime hours. Coverage of showers/storms should be greatest on Thursday and Friday as a weak boundary pushes into the area. Rain chances later decrease over the weekend. Locally higher winds and seas are expected near any thunderstorms that develop. 03 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 98 75 95 74 / 30 40 60 30 Houston (IAH) 97 77 92 77 / 40 40 80 50 Galveston (GLS) 93 80 91 81 / 30 60 70 70 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...03 AVIATION...JM MARINE...03