-- Discussion containing changed information from previous version are highlighted. --
982
FXUS64 KHGX 171954
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
254 PM CDT Mon Jun 17 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
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(This evening through Tuesday Night)
Issued at 216 PM CDT Mon Jun 17 2024

We continue to closely monitor the development of a tropical
disturbance in the Western Gulf of Mexico, which will be the main
driver of a prolonged period of rainfall that will impact SE TX
over the next several days. As of the writing of this discussion,
the National Hurricane Center is assessing the system for a
potential designation as a depression and/or tropical storm.
Regardless of this designation, however, we anticipate impacts
from both excessive rainfall and coastal flooding across portions
of the area, particularly between Tuesday night and Wednesday. A
Flash Flood Watch has been issues for portions of the area, taking
effect at 7 PM tomorrow and remaining in effect through late
Wednesday night.

Synoptic conditions leading into this event will be highly
conducive for periods of heavy rainfall, which at this time will
likely be concentrated roughly along and south of the I-10
corridor. Global deterministic models continue to depict the
west/northwestward progress of the aforementioned surface low,
which, over the course of the next 48 hours, will push into the
Coastal Bend region to our SW. Given the presence of the low, as
well as a robust surface high over the NE CONUS and a developing
lee cyclone in the Central Plains, a strong onshore-oriented
pressure gradient will allow for a deep plume of Gulf moisture to
push onshore. Global models show abundant moisture availability
by tomorrow, with total PW values reaching as high as 2.75 inches
by the evening. With the approach of the disturbance and
associated strong midlevel PVA, we expect scattered showers and
storms to become widespread by Tuesday afternoon, with the
potential heavier bands of rainfall to develop later in the day.
Locally heavy rain may lead to flash flooding in the locations
where the heaviest bands of rainfall develop, with the highest
potential concentrated around the Matagorda Bay region.
Additionally, this prolonged period of rainfall will pose a
hydrologic concern, with rises along area creeks, streams, rivers,
and bayous potentially leading to additional instances of
flooding. Initial rainfall totals through Tuesday evening may
reach as high as 3-4 inches along the immediate coast (see Long
Term section for additional information on rainfall totals).

While winds do not post a primary concern with this system, the
aforementioned gradient winds will produce some gusts in excess of
30 mph across portions of the area. This will lead to the onset
of coastal flooding along the barrier islands, potentially
impacting coastal roadways like Hwy 87. As such, a Coastal Flood
Warning has been issued through Wednesday (see Marine Section
Below).

Cady/Ellis
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&&

.LONG TERM...
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(Wednesday through next Sunday)
Issued at 216 PM CDT Mon Jun 17 2024

The broad low over the West/Southwestern Gulf of Mexico, in
conjunction with deep moisture, will bring thunderstorms and heavy
rainfall to SE Texas through mid week. WPC has a Moderate (level
3/4) to Slight (level 2/4) Risk of excessive rainfall across
portions of SE Texas on Wednesday. The swath of heavier
precipitation should shifts further west on Wednesday, with areas
south of I-10 most at risk for heavy rains and flooding (denoted by
the Moderate Risk area). This includes the Houston Metro area, with
urban locations such as these already prone to flooding due to poor
drainage. These areas could see rainfall totals reach 5-8 inches
through early Thursday, with isolated higher amounts possible. Areas
to the north will generally receive 2-4 inches during this same
period. A Flood Watch will remain in effect across portions of SE
Texas until 1 AM Thursday. This rainfall will likely result in rises
in rivers, streams, creeks and bayous. The main swath of heavy
rainfall may vary greatly depending on the path of the
aforementioned low pressure system. Keep a close eye on the forecast
and make sure to have multiple ways of receiving warnings.

Additionally, near Gale-Force winds and a long fetch over the Gulf
will result in minor to moderate coastal flooding across the Texas
coastline through early Thursday. Coastal locations from High Island
to Freeport will see the greatest impacts from coastal flooding,
with P-ETSS Guidance suggesting water levels rising to 4-5 ft above
MLLW. These locations will be under a Coastal Flood Warning until 1
AM Thursday, while areas near Matagorda bay will remain under a
Coastal Flood Watch for that same time frame. Numerous coastal roads
may be flooded as a result. Low lying property including homes,
businesses, and some critical infrastructure may be inundated in
these coastal areas.

The heavy rainfall threat diminishes on Thursday as the
aforementioned system tracks into Mexico and dissipates. Minor
coastal flooding/inundation could linger until late Thursday
evening. Lighter showers/storms continue daily into the weekend as
an upper level low traverses through the Gulf of Mexico. Ridging
aloft still tries to keep that next disturbance restricted to the
Southern Gulf, and it`s current impacts to SE Texas look minimal.

03
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&&

.AVIATION...
(18Z TAF Issuance)
Issued at 1231 PM CDT Mon Jun 17 2024

Scattered thunderstorms have developed across SE TX this
afternoon, with additional development expected through the early
evening. While conditions should generally remain within VFR
thresholds, storms could temporarily reduce visibilities to sub-
VFR levels as they push through the area. Thunderstorm activity
will taper off heading into the evening hours, with more
widespread rainfall arriving tomorrow as a storm system approaches
the TX coast. These storms will be accompanied by gusty SE winds,
with speeds at times approaching 25 to 30 knots. MVFR cigs are
also expected to develop by tomorrow morning, with forecast cloud
bases around 1500-2000ft.

Cady/Ellis

&&

.MARINE...
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Issued at 216 PM CDT Mon Jun 17 2024

Numerous Thunderstorms, strong winds and high seas are expected over
the next few days due to a tropical disturbance over the
Southwestern Gulf of Mexico. Small Craft Advisories are already in
effect, though winds are expected to rise to 25-30 knots with gusts
up to 35-45 knots late Tuesday/early Wednesday. Seas are expected to
reach 10 to 15 feet at times. These strong onshore winds over a long
fetch will also bring a high risk of rip currents and minor to
moderate coastal flooding across the Texas coastline into late
Thursday. Forecasted winds and seas may vary depending on how this
system evolves. Gale warnings cannot be completely ruled out at this
time. Stay tuned over the next several days as we monitor this
system. Conditions will begin to improve on Thursday as the
aforementioned tropical disturbance dissipates over Mexico, with
winds and seas falling below Small Craft Criteria on Friday.

03
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&&

.PRELIMINARY POINT TEMPS/POPS...
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College Station (CLL)  75  88  74  82 /  20  30  30  60
Houston (IAH)  76  84  74  83 /  30  70  60  80
Galveston (GLS)  81  86  79  87 /  50  90  80  90
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&&

.HGX WATCHES/WARNINGS/ADVISORIES...
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TX...Flood Watch from Tuesday evening through late Wednesday night
     for TXZ197-210>214-226-227-235>238-300-313-335>338-436>439.

     Coastal Flood Warning from 1 AM Tuesday to 1 AM CDT Thursday for
     TXZ214-313-337-338-437>439.

     Coastal Flood Watch from 1 AM CDT Tuesday through late Wednesday
     night for TXZ335-336-436.

     High Rip Current Risk through late Wednesday night for
     TXZ436>439.

GM...Small Craft Advisory until 7 AM CDT Thursday for GMZ330-335-350-
     355-370-375.
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&&

$$

SHORT TERM...Cady
LONG TERM....03
AVIATION...Cady
MARINE...03