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National Weather Service Forecast Discussion

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796
FXUS64 KHGX 231115
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
615 AM CDT Sat May 23 2026

...New AVIATION...

.KEY MESSAGES...

- Flood Watch remains in effect for most of SE Texas.

- Showers and thunderstorms are expected today. Some may be strong
at times. Locally heavy rainfall is possible leading to the
potential of flash flooding. Additional intermittent periods of
rain/storms are anticipated Sunday and Monday for parts of the area.

- Mariners should remain weather aware this holiday weekend. Be
prepared for higher winds/seas in and near storms and allow yourself
plenty of extra time to return to shore before hazardous weather
threatens.

&&

.DISCUSSION...
Issued at 1241 AM CDT Sat May 23 2026

Upper low near Baja will make its way eastward this weekend. In
advance, there will be multiple disturbances in the flow aloft to
trigger shower/thunderstorm activity across the region. Guidance in
these type of patterns is typically less than stellar in terms of
specifics (timing, location, rain amounts, etc) and given the spread
in incoming 00z model guidance, satellite, & radar trends...that
generally holds true in this situation too.

There is considerable uncertainty how everything unfolds today. We
currently have a string of eastward moving, n-s oriented, shortwaves
stretching from the eastern Panhandle to the Hill Country to about
the Big Bend area. Another, stronger looking, disturbance emerging
west of Cabo tracking northeastward into nctl Mexico. In the low
levels, if one squints hard enough, there is a little bit of speed
convergence setting up along the upper Tx coast and some  pooling
1.6-1.9" PW`s. I think with the approach of the shortwave(s) and
heating after sunrise, shra/tstms should blossom as the day
progresses. Suspect everything will eventually be run on the
mesoscale with boundary interactions, cold pools, etc....

In terms of the Flood Watch, considering the overall uncertainty, I
don`t think I could add any value with making adjustments. Generally
speaking, model qpf`s have been on a downward trend for a few
days...now mostly forecasting 1-3" amounts (mostly south of a
Livingston-Columbus line. However, some of the incoming 00z guidance
is still advertising some VERY localized 4-7" amounts. NSSL WRF is
the most concerning one I`ve seen so far...with a swath of high
amounts across the coastal counties in the same spots that saw the
high amounts the other day. There`s a non-zero risk of some
borderline strong/severe cells as well, but overall think rain rates
and downpours will be the more significant risk.

Upper trof tracks into central Tx tonight, and into east Tx Sun-Mon.
Continued chances of rain will persist, with the better chances
east/southeast of where the trof axis is situated (say Matagorda Bay-
Houston-Livingston or so). Would however think the overall coverage
and amounts will be lower and will make downward POP adjustments Mon-
Tue. Things might get active again toward midweek as the next
western trof drops toward the Desert Southwest. 47

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 604 AM CDT Sat May 23 2026

The unstable airmass over our area ended up winning the night,
with moderate to heavy SHRA/TSRA occurring this morning at many
terminals, especially from IAH to the Gulf. This activity should
exit the area over the next couple of hours. However, more
disturbances will be moving over our region later today into
tonight. Of particular interest is a disturbance over northern
Mexico. Heavy TSRA is approaching the Texas-Mexico border this
morning as a result. This disturbance is expected to enter our
area sometime this afternoon. For now, we have SHRA VCTS
prevailing and TSRA TEMPO groups starting around 20-22 UTC. Some
uncertainty regarding how much TSRA will occur overnight tonight.
If storms the atmosphere stabilizes enough, then overnight TSRA
could be limited. But that is not guaranteed. Primary concerns
with any TSRA include frequent lightning, low vis/cig, brief
strong wind gusts, and heavy rainfall.

&&

.MARINE...
Issued at 1241 AM CDT Sat May 23 2026

Look for mainly onshore winds in the 10-15kt and 2-4ft seas to
prevail through the holiday weekend, but with the disclaimer that
wind directions, speeds and seas can and probably will be disrupted
in and near several periods of thunderstorms. Pressure gradient
tightens toward midweek with a corresponding increase in speeds &
wave heights. 47

&&

.HYDROLOGY...
Issued at 306 PM CDT Fri May 22 2026

Multiple rounds of moderate to heavy rainfall are expected this
evening through Monday. The first round will start tonight bringing
2-4 " with isolated higher amounts of 5-6+". With PW values
exceeding the 90th percentile (~1.7-2.1"), rainfall rates of 2-4"/hr
are possible in the heaviest downpours. Anywhere we see these
intense rainfall rates, localized flash flooding is possible. The
greatest concern for the heaviest rainfall is Saturday afternoon
through Sunday morning, but there is the possibly of heavy
downpours through the entire weekend.

Rises to action to minor flood stage are likely though the weekend
especially on flashier responding basins. Isolated moderate to major
stage flooding is not out of the question depending on where the
most rainfall accumulates. We will need to monitor area rivers and
bayous over the next several days to see exactly where the heaviest
rain falls. Remember that you can monitor updated river forecasts
via the NWS NWPS webpage (https://water.noaa.gov/).

Going into next week, we will have monitor the forecast for
additional moderate to heavy rainfall on top of primed soils as this
will generate more runoff than normal. That being said, it is still
too early to tell exactly which basins will have long term issues.

Landry-Guyton

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  84  68  83  68 /  60  50  40  30
Houston (IAH)  84  71  82  70 /  70  70  60  40
Galveston (GLS)  84  75  82  75 /  70  80  70  50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through Monday evening for TXZ164-177>179-197>200-
     210>214-226-227-235>238-300-313-335>338-436>439.

GM...None.
&&

$$

DISCUSSION...47
AVIATION...Self
MARINE...47

NWS HGX Office Area Forecast Discussion