Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
304 FXUS64 KHGX 311151 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 651 AM CDT Sun Aug 31 2025 ...New AVIATION... .KEY MESSAGES... Issued at 1243 AM CDT Sun Aug 31 2025 - An environment supportive of localized heavy rain continues through the weekend. A slight risk of excessive rain (threat level 2 of 4) is in place Sunday, with most of the area seeing a marginal risk for excessive rain (threat level 1 of 4) on Labor Day. - After the holiday, expect rain chances to decrease as drier air filters into the region. Potential for showers and storms may start to work back in late in the week. - High temperatures should remain relatively near seasonal averages; a bit cooler where it rains, a bit warmer where it does not. At night, lows should gradually slide through the 70s towards the upper 60s inland as the drier air filters in. && .DISCUSSION... Issued at 1243 AM CDT Sun Aug 31 2025 If you were a fan of Saturday`s weather around the area, I got some real good news for you about the rest of the holiday weekend, because it`s going to largely be a lot more of the same for the next couple of days. And it`s certainly got its perks, as some folks up around the Pineywoods and east of the Houston metro had temperatures stay in the lower half of the 80s. Of course, the price of that was plenty of showers and storms, which isn`t necessarily ideal for a holiday weekend. Given our, uh...reputation...with holidays though, getting away with a single flood advisory for some heavy street ponding for some inside the Beltway isn`t that bad. Sunday...looks like more of the same. We will continue to have some of the ingredients for heavy rain - a stalled boundary with precipitable water around the 90th percentile, and an upper ridge that has retreated enough that multiple shortwave troughs will be making their way through the pattern in the northwest flow overhead. Soundings indicate a skinny CAPE profile, with sufficient instability for stronger storms in a moisture-laden atmosphere. But...not all of the holes in the swiss cheese model of disasters appear to be lining up, which should mitigate a more widespread heavy rain threat, and keep concerns limited to where/if locally heavy rain falls over a vulnerable spot (low- lying, poor drainage, etc). For instance, Corfidi vectors aren`t terribly alarming - they aren`t really favorably large, but also aren`t indicative of very slow movement and/or backbuilding. We`d instead need other mesoscale features to keep storms from moving, similar to what we saw over the Houston core earlier in the day. Additionally, the low-level moisture transport is somewhat shallow. 925 mb moisture transport vectors are pretty solidly onshore and working at pumping moisture into Southeast Texas, but there`s virtually no moisture transport at 850 mb, instead looking more steady state. Ultimately, there`s certainly some concern for localized flooding issues emerging, and there is a slight risk for excessive rain (threat level 2 of 4) across the area tomorrow as we have a second day with scattered to numerous storms expected to pop up across the area. HREF probabilities for 1 inch per hour rain rates do appear as a speckling of low signal across the area, but perhaps more west of the Brazos and right on the coast than other places. Again, an indication that there`s some support for big rainers there, but no strong signal for any given spot. There was some consideration given to issuing a flood watch, but without the confidence for impacts to a specific area, we`re opting to hold off...for now. Should a better alignment of concerning factors begin to emerge, we could always opt to issue one on a shorter fuse. Monday...more or less run it back. The stalled front does look like it should drift a little farther south, and that will shift low level flow more northeasterly, at least farther inland. This will start to filter in some drier air, but we should still be in a fairly moist environment with continued vort maxes traversing the northwest flow aloft. With a bit of the edge taken off, WPC stepped things back to a marginal risk for excessive rain (threat level 1 of 4) for all but our northernmost reaches, which will be most likely to see the tap turn off as moisture levels start to back down. The rest of the week...doesn`t seem to have quite as much to say about it. Rain potential will back down into the middle of the week, with the initial front pushing off into the Gulf, and a reinforcing front solidly establishing the lack of rain potential arriving late on Tuesday (or early Wednesday?). I don`t think Tuesday is entirely dry, and perhaps not even following days, but whatever rain there is should be pretty scarce. Of course, we can also anticipate daytime temperatures to go up with that as well. While cloudy, stormy Sunday/Monday see highs mostly in the 80s or around 90 at most, we`ll see highs drift back up into the 90s for once the drier air moves in. BUT! the drier air will help the humidity situation be less oppressive, and allow for a bit more cooling at night thanks to the lower temperature floor the decreased dewpoints set! By Wednesday night, I`m forecasting lows in the 60s for all but those right on the Gulf or in the Houston urban heat island. This likely does not mean cool nights for me, but I`m happy for y`all that get them. Now, for the last few nights, you`ve caught me on here trying to be cautiously optimistic about a late week front. And...honestly...a lot of the things that I`ve been pinning my hope on are still there. Anomalously high U winds at 500 mb with anomalously low V winds, 850 temps at or below the 10th percentile pushing as deep as the Red River Valley and parts of North Texas late in the week... I`m not asking for much here, just some days with highs closer to 80 than 90! And yet...the NBM remains stubbornly warm into the weekend, with widespread highs around 90. Even worse, cooler Euro Ensemble 850 temps have pulled back farther north, closer to what NAEFS has been showing. It`s got a forecaster wondering if he`s been wishcasting. And...maybe I am. I do note that LREF`s primary cluster does show a stronger upper trough than the grand mean, and even though it doesn`t appear to have noticeably cooler surface temps anymore, I`d rather a stronger upper trough supporting an incoming front than a weaker one (please do not look at any of the other clusters, which are at best slower and at worst stronger than the grand ensemble mean). So, after all that, I continue to stick near the deterministic NBM numbers, with a slight hedge to the cooler side. I continue to think that the error of the NBM`s forecast will continue to be towards the side of lower temps, but there is not yet enough evidence out there to push me to decisively push the forecast that way, and that error ultimately may not be very large, even if it occurs. && .AVIATION... (12Z TAF Issuance) Issued at 627 AM CDT Sun Aug 31 2025 SGR at MVFR due to CIGs and all other sites at VFR. TSRA/SHRA making their way down from the north and inland from the Gulf this morning. Expect activity to continue through the morning, increasing in coverage this afternoon. Some storms could produce strong wind gusts and locally heavy rainfall as well as reduce VSBYs to MVFR/IFR levels. Winds will generally be light and variable through the period with the exception of winds associated with TSRA. Activity should come to an end this evening with VFR CIGs and light variable winds overnight. && .MARINE... Issued at 1243 AM CDT Sun Aug 31 2025 A stalled frontal boundary will continue to bring scattered showers and thunderstorms to the region through the holiday weekend. Some of the stronger storms will be capable of producing locally heavy rainfall. Winds outside of storms will generally be light and variable. However, locally stronger winds in the vicinity of thunderstorms should be expected. Additionally, the environment will continue to be supportive of isolated waterspouts, and we may see more on top of those observed during the day on Saturday. While rain chances should dwindle inland, daily isolated to scattered showers and storms may persist over the Gulf. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 83 72 87 71 / 80 40 50 10 Houston (IAH) 85 75 89 74 / 60 30 50 20 Galveston (GLS) 87 79 87 79 / 50 50 70 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...Luchs AVIATION...Adams MARINE...Luchs