textproduct: Houston/Galveston

KEY MESSAGES

- Periods of showers and thunderstorms are expected through early Sunday. Locally heavy rain will be possible and could lead to instances of flash flooding.

- A Flood Watch remains in effect for portions of Southeast Texas through Friday evening.

- Daytime temperatures are expected to drop to more seasonal levels in response to rain and increased cloud cover.

- Cold front pushes through early next week bringing drier air and slightly cooler temperatures.

DISCUSSION

Issued at 1242 AM CDT Fri Oct 2 2026

If you recall in last night's discussion, we talked about how the boundary had an 80ish mile range of where it could set up. Even that buffer wasn't large enough as the boundary ended up making it further south into Jackson County and stretching northeastward through Fort Bend/Harris Counties and up into the Piney Woods region. The late afternoon high-res model guidance was indicating the potential for 6-8+" along this boundary as it stalled overnight, which prompted the southward/eastward expansion of the Flood Watch. WoFS initialized very well and was accurate in its depiction of where the boundary would stall. Keep in mind that PW values are still near or above the MAX percentile (~2.3") and there continues to be lift from both the boundary and embedded shortwaves...and divergence aloft from being near the right entrance region of a jet streak. Plenty of instability remains as well (MLCAPE: 1000-1500 j/kg).

Speaking of the WoFS (and the latest HRRR) runs, they both indicate periods of moderate to occasionally heavy rain continuing through the 4-5am timeframe right along the boundary followed by gradual dissipation through the rest of the morning. The issue is that areas along the boundary have already received 4-7+" or rainfall as of late Thursday night (~12am-ish). The rainfall rates have been mostly manageable this evening, but the potential for localized heavy rainfall (rain rates of 3-4"/hr) continues through early Friday morning and could lead to instances of street flooding in urban areas. The dry soils should keep rural areas from seeing flooding issues unless heavy rains fall for an extended period of time...which isn't out of the realm of possibilities in this environment. A Flood Watch remains in effect for portions of Southeast TX through this evening.

Be sure to check the latest Excessive Rainfall Outlook graphics on either our webpage or WPC's webpage, but as of late Thursday night, the moderate risk (level 3 of 4) was expanded further eastward to include most of the Brazos Valley and the Piney Woods with a slight risk (level 2 of 4) elsewhere. With convection being rather sparse throughout the late morning into the early afternoon, the flood threat will be limited to areas that received the bulk of the rainfall Thursday night (generally along and west of I-45. Most of this area is in a marginal to slight risk in the ERO. Scattered showers and storms look to develop in the afternoon hours once daytime heating gets going, but keep in mind that we'll still have the frontal boundary somewhere in the vicinity. It gets pretty washed out (that pun was not intended), so it's tough to tell exactly where it'll be on Friday afternoon. Cloud cover up north will help keep temperatures in the low to mid 80s for highs. Further south, there will be enough breaks in the clouds to get temperatures to peak in the upper 80s to low 90s.

Before we get into the discussion about the heavy rain potential that comes over the weekend, I briefly want to discuss the synoptic environment. By Friday morning, an upper level low will cutoff from the tail-end of an upper level trough over west TX. The upper low is expected to remain nearly stationary before getting embedded in the flow aloft later this weekend. While this is occuring, a coastal low/trough in the western Gulf will be gradually lifting northward. Areas south of I-10 and the Gulf waters will be placed in the middle of the moisture axis from the upper trough/low (and associated frontal boundary) and the coastal trough/low. So, this puts our attention on our coastal areas over the weekend as this two features interact.

The aforementioned frontal boundary will be somewhere in the vicinity of Southeast TX over the weekend. As we talked about before, it's very hard to tell exactly where it'll be as the winds become easterly from south to north with the approach of the coastal trough/low on Saturday. With PW values remaining near the MAX percentile, the nearby frontal boundary, and embedded shortwaves, this brings us to our next potential for heavy rainfall late Saturday into Sunday mainly along the coast.

This is the result of moisture converging along the front and the coastal trough/low drifting northward through the northwestern Gulf. Two sources of moisture coming together will essentially act as a sponge wringing itself out. The question for now is does that occur close enough to the coast to bring heavy rain/flooding concerns. The answer to that remains uncertain. Rainfall totals south of I-10 are generally anticipated to be in the 2-4" range Saturday through early next week. However, just a few miles off the coast is ~6+" rainfall totals. The majority of this rainfall will occur late Saturday into Sunday as the coastal low/trough approaches the coast. It's worth noting that there's some deterministic guidance that forms a surface low while others keep an open trough...it remains to be seen which of these plays out. Either way, areas south of I-10 will have the highest rain chances...especially right along the coast. Resultingly, WPC has marginal to slight risk for Saturday and Sunday with the main risk being for the coastal counties. Keep in mind that this is a scenario where most of the rainfall may end up occuring just off of the coast...a ~10-20 mile margin of error will make a big difference here.

Not gonna lie...things have been fairly busy this evening with ongoing rainfall and I'm technically in active hydro warning operations as I type this, so the rest of the AFD is copy pasta from last night's since next week's forecast remains on track. Work smarter, not harder! :)

Elevated moisture persists along the coast going into early next week, and then...IT HAPPENS! I wish I could do a balloon drop with confetti but I'm limited to just text, so just use your imagination when I say this next sentence. A cold front is expected to push through Southeast TX early next week and usher in drier and cooler conditions! (*cue the confetti*)

An upper level trough is expected to dip down into the northern/northeastern CONUS. A cold front will push through the eastern CONUS with a 1026-1028mb surface high in its wake. It looks like we'll get the tail-end of this front around the Monday/Tuesday timeframe. This won't be a substantial cooldown by any means, but it will be a noticeable one. The probability for low temperatures below 70 degrees for the city of Houston goes from 0% through the weekend to ~60% for most of next week after Monday. This may end up being a "False Fall" (slightly cooler temperatures followed by a return to above normal temperatures), but I'm gonna enjoy every second of seasonal temperatures! I got so distracted talking about the temperatures that I forgot to mention that the drier air means that rain chances are mostly gone except right along the coast behind the front since that one too looks to linger just offshore.

Batiste

AVIATION

(12Z TAF Issuance) Issued at 703 AM CDT Fri Oct 2 2026

Winds are light and variable, turning to the NE and strengthening this afternoon around 10 kts. The boundary which provided heavy rain and lowered flight conditions yesterday is dissipating this morning before daytime heating reignites afternoon rain chances. These storms are still moisture-rich, meaning locally heavy downpours are possible and gusts could be elevated around these storms. Ceilings are mostly FEW-SCT between 2000-3000 ft but these could fill in to MVFR as storms develop this afternoon, and even lower intermittently to IFR. Storms should die out between 00Z - 02Z Saturday and winds drop to light and variable, except along the coast and bays where they remain around 10 kts. Speaking of, we're watching for SH/TS to develop along the coast late tonight and linger inland throughout the day Saturday, likely providing lowered flight CIGs and VIS.

BSM

MARINE

Issued at 1242 AM CDT Fri Oct 2 2026

Scattered to numerous showers with isolated thunderstorms will continue today as a slow-moving disturbance moves over southeast Texas. Rain and storm chances will continue through the weekend, peaking early next week with the frontal passage and surface coastal trough along the middle TX coast. Overall, moderate onshore winds and building seas (3 to 5 ft) will persist through the weekend. Elevated winds and seas around 7 ft, occasionally higher will be possible Monday and Tuesday with the FROPA. A Small Craft Advisory will likely be needed late Tuesday or Wednesday. In terms of beach conditions, will continue to monitor water levels, which will peak around 3.0 - 3.3 ft MLLW, particularly during times of high tide through at least Sunday.

JM

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 83 70 84 69 / 70 40 80 60 Houston (IAH) 89 75 87 74 / 60 30 80 60 Galveston (GLS) 89 80 86 78 / 50 60 90 90

HGX WATCHES/WARNINGS/ADVISORIES

TX...Flood Watch until 7 PM CDT this evening for TXZ177-195>199- 210>213-226-227-235-313-335.

GM...None.