textproduct: Houston/Galveston

KEY MESSAGES

- Gusty onshore winds are occurring today, making for some rough marine conditions on area bays and coastal Gulf waters, where a small craft advisory is in effect.

- The onshore winds are also building a pool of moisture ahead of a cold front tonight. Light scattered showers are already cropping up, but rain chances will peak later tonight. There is a marginal risk for a severe storm and/or heavy downpours - roughly a 5-15 percent chance.

- An even chillier airmass comes in following the weekend front, opening December on a cold note. We can expect to see the return of nights with temperatures reaching lows around or just below freezing to a portion of the area, most likely north of the Houston metro.

DISCUSSION

Issued at 149 PM CST Sat Nov 29 2025

After spending several days speculating and hypothesizing about how this frontal passage is going to play out, we are very nearly to it actually happening! This time yesterday, I was noting that we were still dry, but with strong onshore flow, you could already see the signs of deepening moisture...and that was with a precipitable water range of 0.4 to 0.8 inches. Now, we've built up to a range of 1.2 to 1.4 inches, or roughly 150 percent of normal.

With that moisture, we're already starting to see some scattered showers around the area, thanks to some assistance from a weak pre-frontal trough interacting with the subtlest of upper shortwave troughs moving through (genuinely, I don't think I could pick it out on WV imagery without getting model analysis telling me it was there!).

Looking ahead through the rest of the night, and the big push of moisture is really going to be the thing that stands out to me for the environment ahead. The best upper support for precipitation is far, far, far to our north - responsible for helping out with snow falling on college football games in the Upper Midwest this afternoon. Over us...I can at least see signs of some cyclonic flow over North Texas that will help support activity through tonight, but even that is quite subtle as flow aloft remains virtually zonal. But hey, at least I can spot it in the satellite imagery without the rainfall and models telling me something has to be there?

Despite the lack of "dynamic" support, we do still have lots of moisture by late November standards, and a front that should still be well shoved through by strong high pressure behind it. So...for all the pooh-poohing I've done of the current setup, I'm still quite confident that we'll see numerous showers and some thunderstorms flare up ahead of and along the front as it moves in tonight. I'm also growing more confident in the stance we've been taking this week on these storms is all around a pretty solid one still. There are some things that stand out to me as supportive of a noticeable impact: well above average moisture; a focus for sustained convection from the front; a big, looping hodograph at low levels. Indeed, the 12Z HREF this morning painted some isolated 5-7" totals over parts of Harris County.

At the same time, I see some big limiting factors for an organized severe/heavy rain threat: moisture that while above average, is not extreme; a progressive nature to the rainfall; background drought and low bayou levels; poor upper support for storms; shear and instability parameters that are more "eh, I guess that's enough" than "wow, look at that".

Ultimately, I would be entirely unsurprised with an isolated strong to severe storm, and some localized minor flooding should one of the bigger rainers happen over the wrong spot. Shear and instability are enough that we could get a little mini-supercell in this mess that makes a run for severe thresholds or even may produce a brief, relatively weak tornado. And at the same time, the limitations on the environment keep the threat for any given specific spot fairly low, as these will be the threats from only the very strongest of the night's storms. For many of us, we'll be dealing with sub-severe storms and rain that, if anything, is probably welcome.

If I were going to highlight a spot to have some more concern, I'd pick poor-drainage spots in the urban core of Harris County. Should we see those 5-7" maxes materialize, *and* if the bulk of that comes rapidly in an hour or two from a particularly strong storm, that could cause some localized issues. Rain rates are really going to be the key here - to cause problems, we'll need a storm that can really fully realize every bit of the available moisture.

There was some discussion with WPC about introducing a small slight risk area for excessive rain over the Houston metro for this precise outcome. And...had we been in the warm season where 150 percent of normal PWATs could easily support multiple inch per hour rain rates, I think we would have done it. For tonight, though, the ultimate determination was that the probability would fall just shy of that 15 percent threshold to bump up a risk category. But we're close. If you're going to be out and about very late tonight and/or very early this morning in Houston, be particularly alert around those locations you know take on water before anywhere else. If there's a problem anywhere, it'll be there.

After tonight, things look to chill out...but more in the literal sense. Another shot of cold air surges in behind this front, and we can likely expect temperatures back down around where they were for our one (1) cold stretch we've had this fall. On the one hand, that is chilly and it'll be time to pull those hoodies and jackets back out. On the other hand, it has me feeling a little better about ruling out the coldest potential scenarios I'd brought up the past couple of days. Where the NBM's 13th percentile lows brought temps right around freezing across all of Southeast Texas, now even here it keeps freezing temps north of the metro, and creeping down into the rural areas well west of the metro. The urban core and the coast, while still chilly, look increasingly unlikely to get all the way to freezing.

What's most likely still is what we'd discussed previously as the most probable outcome - a couple chilly days and nights to start the week, with freezing temps mostly confined to well north of Houston. And then...with a pretty progressive pattern holding, we'll look for our next round of rain. That looks to be as early as Monday with another upper disturbance rolling through, potentially spinning up a very weak coastal trough. This would also help stave off the coldest scenarios, but at a price - it'd still be chilly, so be on the lookout for a raw, chilly, wet Monday. Real good "staying inside with soup or chili" kinda day. After that moves off, we get a short stretch of fair weather and a bit more warmth, but the cycle keeps on moving, so onshore flow returning Wednesday will begin us on the moisture return train back to another shot at rain and storms towards the end of the week.

AVIATION

(18Z TAF Issuance) Issued at 1135 AM CST Sat Nov 29 2025

A somewhat convoluted TAF forecast for the next 24 hours as passing showers move over Southeast TX during the day today, followed by an increase in showers showers and thunderstorms tonight into early Sun as a cold front moves across the region. Strong storms will be capable of producing strong VRB winds, lightning, llvl shear, and reduced vis/cigs leading to IFR-MVFR conditions. Showers will gradually taper off a few hours after the frontal passage during the morning hours. S winds at 10-15KT with gusts of around 20KT expect this afternoon, then relax to 5-10KT. In the wake of the front Sun morning, expect N-NW winds at around 15KTS with gusts of around 25KTS. Coastal locations may see gusts of around 30 KTS. IFR-MVFR cigs may prevail into the early afternoon hours for several sites.

Cotto

MARINE

Issued at 149 PM CST Sat Nov 29 2025

Moderate to strong southeast winds and elevated seas continue today. Small Craft Advisories are in effect across all area waters this afternoon. The rough conditions should modestly improve through the evening as a cold front approaches the region. However, the front will also have associated showers and thunderstorms, expected to reach the bays very late tonight, then push over the Gulf waters early Sunday morning. Some of the storms could be on the strong side. Moderate to strong north winds can be expected in the wake of the front, and a new round of small craft advisories may be needed. Another upper level disturbance will move through Sunday night and Monday bringing another round of rain and embedded thunderstorms.

At the coast, stronger onshore winds will push tidal levels above astronomical norms, but for now appear to stay below 3 feet above MLLW, which should largely preclude any coastal flooding issues. The strength of the onshore winds will be more effective in generating dangerous rip currents at Gulf-facing beaches, and a rip current statement is in place for that danger.

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 74 41 49 41 / 90 80 10 30 Houston (IAH) 76 49 54 44 / 40 70 30 40 Galveston (GLS) 76 58 63 51 / 10 70 60 40

HGX WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk through Sunday morning for Txz436>439.

GM...Small Craft Advisory until 6 PM CST this evening for Gmz350-335- 350-355.

Small Craft Advisory until 9 PM CST this evening for Gmz350-375.