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National Weather Service Forecast Discussion

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197
FXUS64 KHGX 020545
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1245 AM CDT Fri Oct 2 2026

...New KEY MESSAGES, DISCUSSION, AVIATION, MARINE...

.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...
(06Z TAF Issuance)
Issued at 1242 AM CDT Fri Oct 2 2026

The boundary has pushed east into the region, and is starting to
stall. It is still oriented from NE to SW, and the heaviest rainfall
is generally at the leading edge of the boundary. Light to moderate
rainfall is expected with occasional heavier downpours for most TAF
sites. This rainfall will last well into the overnight hours. MVFR
level CIGS prevail at many sites, though they are mostly SCT in
nature. In those brief heavier downpours, CIGs could fill in to meet
MVFR thresholds. Several METARs have reported FEW005-010. These
lower clouds are not expected to fill in, though some sites may
experience brief IFR CIGs tonight. Winds have decreased and become
VRB this evening, though some storms at the leading edge of the line
are producing outflow boundaries. A brief gust can`t be ruled out.

It`s looking like there will be a break in the rain tomorrow
morning, where storms become much more isolated in nature. By this
point, winds turn out the NE and CIGs remain low-end VFR. Tomorrow
afternoon, storm chances and coverage increase once again. Similar
to today, these storms will be in a moisture rich environment, and
will therefore be capable of producing heavy downpours. Winds
increase and remain out of the NE. Shower/storm activity is expected
to decrease by tomorrow evening, though showers may linger into the
evening near the coast.

MLG

&&

.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)  70  84  69  82 /  40  80  60  60
Houston (IAH)  75  87  74  83 /  30  80  60  60
Galveston (GLS)  80  86  78  85 /  60  90  90  90

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through this evening for TXZ177-195>199-210>213-226-
     227-235-313-335.

GM...Small Craft Should Exercise Caution until 7 AM CDT this morning
     for GMZ330-335-350-355-370-375.

&&

$$

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

NWS HGX Office Area Forecast Discussion