FXUS64 KHGX 011104 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 604 AM CDT Thu Oct 1 2026 ...New AVIATION... .KEY MESSAGES... - Periods of showers and thunderstorms are expected each day, peaking today through early Sunday. Locally heavy rain will be possible and could lead to instances of flash flooding. - The heavy rainfall threat shifts from the Brazos Valley on Thursday/Friday to the coast on Saturday/Sunday. - 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. && .DISCUSSION... Issued at 1216 AM CDT Thu Oct 1 2026 If you wanted to be woken up when September ended, then this is your wake up call. There's a lot you missed out on, but you won't want to miss out on being informed for what's to come to kick off October with the potential for heavy rainfall/flooding across portions of Southeast TX over the next few days. With that in mind, we'll break things up into two sections again. We'll focus on the Brazos Valley portion of it first (Thursday/Friday), then on the coastal heavy rain/flooding potential that comes over the weekend. This'll be another long read...I believe the 5th or 6th novel in the Southeast TX forecast series...you've been readily warned! Let's begin! ------------ Heavy Rain Event #1 {Brazos Valley - Thursday/Friday}: Let's start with what's currently going on. An upper level trough with an embedded upper low is currently situated right over NM. This is as good of a spot as any to mention that the remnants of Polo have been fully merged with the trough and if you take a gander at mid or upper-level water vapor imagery, it's pretty clear where the moisture axis is. The associated surface low is right around the OK/KS border with a cold front extending down through the TX panhandle...the latter of these features will be a key character in both of these heavy rain events. A 30-40 kt nocturnal LLJ will develop overnight and extend southwest to northeast from central TX to eastern OK. This keeps the main region of lift to our west/northwest coinciding with the slow-moving cold front that gradually pushes southeastward through the northern/central parts of TX. So, the heavy rainfall axis tonight through Thursday morning will be relegated to along the front and stretching a bit further southwestward into portions of the Hill Country (thanks to divergence aloft). While we still have the LLJ fresh in our minds, let's briefly talk about the overnight winds. Winds aloft in our area will mainly be in the 25-35 kt range, but we'll be de-coupled (as we usually are at night). Areas along the coast will not be though, which means some of these winds will be able to mix down to the surface. Coastal areas around Matagorda Bay will likely see the highest gusts overnight, which may occasionally peak around 30 mph through early Thursday morning. Sustained winds may briefly reach 25 mph at times, but it's a small enough area that may see these elevated winds to not warrant the issuance of a Wind Advisory. Going into Thursday, PW values will begin to peak above the MAX percentile (~2.3") for portions of the Brazos Valley and the Piney Woods. This is when we'll be closely monitoring the progression of the frontal boundary along with any embedded shortwaves. The aforementioned LLJ will be gradually decaying through the early afternoon hours, but we'll remain in an area of divergence aloft till it completely subsides. Pairing that with a shortwave will result in a slow moving line of showers/storms that looks to push through portions of the Brazos Valley in the afternoon. Discrete showers/storms are definitely in play south of this line, so those of us in the southern half of the CWA have a chance at getting some rain as well. I probably should've mentioned that I'm basing the previous paragraph and this one on the 00Z CAMs...Cam forgetting to mention the CAMs...there's some irony in there somewhere. Anyway, once the initial line of convection dissipates in the late afternoon, another round of convection develops overnight into Friday morning. This is where things are still a little unclear, but let's talk about what we do know. Model guidance is still onboard with an upper low cutting off over west TX from the upper level trough by early Friday morning. The placement of this low and its associated band of shortwaves will play a huge role in where this second round of convection occurs. Training convection appears to be likely, so this is where the flooding threat takes shape. Oh and the location of the front is also important here too for frontogenetic forcing reasons. Based on model guidance, this heavy rain axis could be anywhere from northwest of Burleson/Brazos Counties to down in Colorado/Austin counties stretching northeastward. That's roughly an 80ish mile difference, so you can see why this is an incredibly frustrating forecast. All that being said, the potential is there for heavy rainfall/flooding Thursday night into Friday. The greatest potential remains to our northwest though. Most of the 00Z high-res guidance keeps the bulk of the heavy rainfall to our northwest. While there are a couple of solutions that bring higher rainfall totals (4+") to portions of the Brazos Valley, there is too much uncertainty to warrant the issuance of a Flood Watch. Additionally, we've been pretty dry lately, so the grounds can take on quite a bit of rain before we'd need to worry about runoff. This wouldn't be the case for urban areas if prolonged periods of heavy rainfall were to occur (*looks over at Aggieland*). While the potential is definitely there, the confidence is not...so no Flood Watch. The flooding threat is NOT zero though. Please don't let that be your takeaway. Rainfall rates could still easily peak above 3-4"/hr in the heaviest downpours. These rainfall rates for an extended period of time could quickly lead to issues, especially in urban areas and areas with poor drainage. WPC has maintained a marginal to slight risk of excessive rainfall Thursday through Sunday for portions of Southeast TX. A moderate risk (level 3 of 4) has been expanded to portions of Burleson and Brazos Counties for Thursday into early Friday [this is true as of late Wednesday night]. The most widespread risk (where all of Southeast TX is outlined) is on Thursday and Friday with the flood risk shifting to the coast over the weekend. See the latest Excessive Rainfall Outlook graphics on either our webpage or WPC's webpage for specifics for your particular location. In terms of rainfall totals, we are still anticipating 2-4" for the Brazos Valley/Piney Woods and 0.5-2" elsewhere through Friday afternoon. Locally higher totals are certainly possible especially in portions of the Brazos Valley. There is enough moisture and lift in place for scattered afternoon convection across the area on Friday. Our attention then turns to coastal areas over the weekend as the frontal boundary gradually pushes through the region. ------------ It's time to stand up for the seventh inning stretch! Unfortunately there's no more baseball left to be played in Houston, but at least you don't have to worry about me singing. I will remind you though to visit www.weather.gov/houston to stay up to date on the latest local forecasts for Southeast TX, but also be sure to visit www.wpc.ncep.noaa.gov to stay up to date on the latest Excessive Rainfall Outlooks and to see their very detailed discussions! ------------ Heavy Rain Event #2 {Coastal Areas Saturday/Sunday}: The aforementioned frontal boundary gradually pushes through Friday, but is expected to linger near the coast going into the weekend. With PW values remaining near the MAX percentile, a nearby front, 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 a 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 for now is...maybe? 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. Once we get in the range of high-res guidance, the picture should become a bit more clear on how this event will play out. I wouldn't be entirely surprised for us to end up with higher rainfall totals along the coast versus in the Brazos Valley, but the reverse result could also easily occur. 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 could make a big difference here. 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 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. Our wishcast has made it into the forecast now! Look at us go y'all! 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. I should probably also mention that temperatures on Thursday will top out in the low 90s followed by the 80s the rest of the way thanks to the increased rain chances and the aforementioned frontal passage early next week. Batiste && .AVIATION... (12Z TAF Issuance) Issued at 603 AM CDT Thu Oct 1 2026 Scattered showers/storms expected across the region today, but timing & coverage around any individual terminal is problematic so broadbrushed PROB30s for most areas. Exception would be across NW parts of the area (CLL area) who should see increasing precipitation coverage later in the day...and probably a more organized line of convection track in from the west. Heavy downpours, reduced vsby/cigs, and some gusty winds are very possible there late this afternoon into the evening. Guidance suggests coverage shrinking and weakening during the late evening and overnight. Outside any tstm activity, VFR conditions should prevail. 47 && .MARINE... Issued at 1216 AM CDT Thu Oct 1 2026 Moderate southeasterly winds and gradually building seas (peaking in the 5-7 ft range) will persist through late Thursday. A Small Craft Advisory is in effect for the bays and Gulf waters through at least Thursday morning, but caution flags may be needed following this through Thursday night. Water levels beginning tonight/early Thursday morning week peak around or just above 3.0-3.3 ft MLLW during high tide over the next few days, so not enough for coastal flooding hazards but high enough for mariners to take note. Daily chances of showers/storms continue especially during the overnight to early morning hours over the Gulf. Expect rain chances to increase starting on Thursday as an upper level disturbance pushes into TX along with a slow-moving frontal boundary. Rain chances look to peak over the weekend along the coast and the Gulf as a frontal boundary and a coastal weather system interact. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 93 73 84 70 / 70 90 90 70 Houston (IAH) 92 77 89 74 / 60 50 80 30 Galveston (GLS) 90 82 89 80 / 30 40 60 80 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through this evening for TXZ436>439. GM...Small Craft Advisory until 10 AM CDT this morning for GMZ330-335. Small Craft Advisory until 1 PM CDT this afternoon for GMZ350- 355-370-375. && $$ DISCUSSION...Batiste AVIATION...47 MARINE...Batiste