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National Weather Service Forecast Discussion

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597
FXUS64 KHGX 202312
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
612 PM CDT Mon Jul 20 2026

...New AVIATION...

.KEY MESSAGES...

- Hot conditions persist through the week with the hottest days
  Tuesday and Wednesday.

- A Heat Advisory is in effect from 11 AM - 8 PM Tuesday.

- NHC is monitoring the development of Tropical Depression Two,
  currently in the northeast Gulf. While forecast uncertainty
  remains fairly high, residents should monitor the latest
  forecasts and evolution of this system.

- Corresponding rain and temperature forecasts for the local area
  are subject to changes later in the week and highly dependent on
  the tropics.

&&

.DISCUSSION...
Issued at 225 PM CDT Mon Jul 20 2026

Hot and humid conditions continue this afternoon as high pressure
remains anchored over the region. Water vapor and visible satellite
imagery depict  a prevailing drier airmass and broad subsidence
dominant across the area. Afternoon temperatures will climb into the
mid 90s. When combined with sfc dewpoints in the 70s, heat indices
will reach up to  107F, close to advisory levels. Be sure to
practice heat safety if spending extended periods outdoors!

The main weather story for the first half of the week continues to
be the heat. A robust ridge of high pressure will remain anchored
across the central and western CONUS, providing sufficient
subsidence locally to keep highs on a steady upward trend. Some
inland locations will likely see their first 100-degree day of the
year by Tuesday or Wednesday. Simultaneously, low to mid-level
moisture filtering inland from the Gulf will keep humidity levels
elevated. The combination of hot and humid conditions will push peak
heat index values into the 107 to 112F range Tuesday and Wednesday.
A Heat Advisory has been issued for all of southeast Texas for
Tuesday from 11 AM - 8 PM. Wednesday is shaping up to be even hotter
(likely due to the approaching tropical system over the Gulf).
Therefore, advisories will likely be extended in future forecast
updates.

Heading into Thursday - Saturday, attention turns toward the Gulf
regarding the evolution of Tropical Depression (TD)Two. The mid to
upper level ridge positioned to our northwest will serve as the
primary steering focus, nudging the system on a general westward to
west-northwestward track toward the northwestern Gulf. However,
environmental factors including dry air entrainment and shear
could influence the system`s track and intensity. Please, see the
Tropical discussion below for further details on this system and
potential impacts for Southeast Texas.

Forecast beyond Saturday remains sensitive to the final track and
strength of TD Two. Well-above normal temperatures will be possible.
Will continue to monitor for heat headlines through the weekend.

JM

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 611 PM CDT Mon Jul 20 2026

VFR conditions and light winds will prevail. Winds will transition
from the ssw this evening, to the wsw overnight into early
afternoon, then back to the sw/ssw late in the day). There was
some patchy fog around earlier this morning, but fcst soundings
show a bit drier llvl conditions...so other than some rural
locations mainly west of I-45, most terminals shouldn`t see
significant vsby drops. 47

&&

.MARINE...
Issued at 225 PM CDT Mon Jul 20 2026

Surface high pressure will continue to bring light to occasionally
moderate west to southwest winds and low seas across the Upper TX
coast. Mariners should continue to monitor weather conditions,
especially toward the end of the week as Tropical Depression Two
moves westward along the northern Gulf. This system is forecast to
strengthen into a tropical storm later today as it approaches
southeast Louisiana, before weakening again into a tropical
depression as it moves toward the Upper Texas coast Thursday and
Friday. While forecast confidence remains low, given high
uncertainty in track and intensity; significant impacts are not
anticipated across our coastal waters. However, Small Craft
Advisories could potentially be issued during this period with
elevated winds and seas up to 6 ft (offshore).

JM

&&

.TROPICAL...
Issued at 329 PM CDT Mon Jul 20 2026

As of 3 PM CDT, Tropical Depression Two continues to meander
slowly northwestward in the northeastern Gulf. The system has
become better organized relative to yesterday, featuring an
increase in banding features as well as an uptick in deep
convection near, though not completely collocated, with the
center. Moderate upper-level shear and dry air continue to limit
the rate of further organization. However, these conditions are
not expected to prevent strengthening. Therefore, the depression
is forecast to become a tropical storm later tonight or tomorrow
as it continues its slow, northwestward drift.

By Wednesday, a building ridge is expected to steer the system
westward, placing it on a trajectory towards southeast Texas. The
primary meteorological question for our area will be whether or
not the system can survive the atmospheric and geographical
hurdles that lie ahead of it. For starters, the system is expected
to track near or over southern Louisiana, limiting its
intensification due to land interaction. In addition, the
building ridge will increasingly supply north to northeasterly
wind shear. This would tend to decouple the mid-level circulation
from the lower levels, weakening the system as it approaches
southeast Texas. There`s also the current entrainment of dry air,
which coupled with the shear is resulting in an exposed center
that is not collocated with the deep convection.

Due to these environmental factors, the National Hurricane Center
is predicting that the system will weaken back to a depression as
it approaches southeast Texas towards the end of the week. That
being said, we continue to strongly advise the public to monitor
the forecast in case trends change.

Self

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  72  98  78 100 /   0   0   0   0
Houston (IAH)  75 100  80 102 /   0   0   0  10
Galveston (GLS)  79  94  81  95 /   0   0   0  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory from 11 AM to 8 PM CDT Tuesday for TXZ163-164-
     176>179-195>200-210>214-226-227-235>238-300-313-335>338-
     436>439.

GM...None.

&&

$$

DISCUSSION...JM
AVIATION...47
MARINE...JM

NWS HGX Office Area Forecast Discussion