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020
FXUS64 KHGX 010516
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1216 AM CDT Thu Oct 1 2026

...New DISCUSSION, AVIATION, MARINE...

.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...
(06Z TAF Issuance)
Issued at 1216 AM CDT Thu Oct 1 2026

Gusty winds remain for northern TAF sites. Otherwise, SE winds
continue to decrease to the 8-10 kt range overnight. Early tomorrow
morning, an MVFR level cloud deck will likely impact KCLL and KUTS,
and could reach KCXO as well. Expect MVFR CIGS at FL020-030
beginning at around 14Z at KCLL, then moving eastward through the
early morning hours. A boundary pushes east into our region,
increasing chances for showers and thunderstorms tomorrow afternoon.
Storms will be numerous in nature. Showers may start as early as
14Z, with the peak of thunderstorm activity being in the afternoon
hours. Because of the excess moisture available to these storms, any
showers/storms that do develop may be capable of producing heavy
downpours, limiting VIS at terminals. Intermittent MVFR CIGs may
develop with these storms, with low-end VFR CIGs prevailing. SE
winds increase back to the 10-15 kt range, gusting to 20 kts near
storms. Thunderstorm activity looks to start tapering off towards
the evening, though isolated SHRA activity is expected to persist
well into the overnight hours for tomorrow. Looking ahead of this
TAF package, a second line of storms is expected to develop early on
Friday morning. Again, these storms may be capable of producing
heavy rainfall. Another PROB30 group will likely be included in the
following TAF package.

MLG

&&

.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 /  80  90  90  70
Houston (IAH)  92  77  89  74 /  70  50  80  30
Galveston (GLS)  90  82  89  80 /  40  40  60  80

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until noon CDT today for TXZ436>439.

GM...Small Craft Advisory until 10 AM CDT this morning for GMZ330-335-
     350-355-370-375.

     Small Craft Should Exercise Caution from 10 AM CDT this morning
     through Friday morning for GMZ330-335-350-355-370-375.

&&

$$

DISCUSSION...Batiste
AVIATION...MLG
MARINE...Batiste

NWS HGX Office Area Forecast Discussion