Flash Flood Warning 13, NWS Houston/Galveston, TX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
123 AM CDT Tue Jun 16 2026

...New DISCUSSION, MARINE, TROPICAL...

.KEY MESSAGES...

- Life-threatening flooding remains possible through Wednesday. An
  additional 4-10" is possible. Rainfall rates have exceeded 2-5"
  per hour in some locations.

- Trough/Low may drift into the northwest Gulf today. 60% chance
  of tropical development. Moderate to strong winds could develop
  over the coastal waters. Cannot rule out gusts possibly to Gale.
  Tropical funnels and waterspouts will also be possible along
  the coastline.

- Moderate to high risk of rip currents each day. Elevated tides
  may lead to minor coastal flooding, especially on
  Wednesday/Thursday.

&&

.DISCUSSION...
Issued at 1154 PM CDT Mon Jun 15 2026

Life-threateing Flash Flooding remains possible across portions of
SE Texas over the next few days. Currently seeing a short lull in
rainfall early today, but anticipate activity to pick back up
heading into the daytime. SE Texas remains engulfed within a deep
tropical airmass, featuring some of the highest TPWs on recored for
this time of the year, around 2.1-2.6 inches. Forecast soundings are
still primed with a classic heavy rainfall signature from the deep
saturation, thin parcel traces showing modest instability, and a
deep warm cloud layer over 16,000ft. Corfidi upshear wind vectors
drop to around 10 knots early this morning, with downshear values
falling to 10-20 knots during portions of the late morning and early
afternoon. Both of which seem to hover around 10-25 knots in the
evening into Wednesday. A frontal boundary remains stalled out over
the region, with a front-right entrance region of a longwave trough
overtop the area as well. We should get an injection of drier air
aloft above 700mb this evening, pushing midlevel RH to 60-70% in the
Houston area by Wednesday. Drier conditions to the north should
result in some mitigation of the flooding risk over those areas,
though coastal bound locations, including the Houston area, will
remain shrouded within a potent tropical airmass.

Another layer of complexity and uncertainty with this forecast comes
from a trough of low pressure, currently situated over the eastern
Texas/Mexico boarder. This system is expected to push
north/northeast, potentially emerging over the the northwest
Gulf/Texas coastal today/early Wednesday. Once over the Gulf waters,
this low could deepen and potentially organize into a tropical
storm. NHC now gives this system a 60% chance of tropical
development within the next 48 hours. Model guidance still has a
very mixed handle on this low, with wide variations in timing. Even
if this low doesn't develop into a tropical storm, it will still
amply heavy rainfall across the Texas coastline.

WPC maintains a Moderate (level 3/4) Risk of Excessive Rainfall over
the Texas coastline through early Thursday morning. An additional 4-
10 inches of rainfall are possible through early Thursday morning.
Rainfall rates of 2-5"/hr are expected, though these rates could be
even higher in spots, as observed on Monday. Life-threating flash
flooding will likely occur. Urban and low lying areas will be
especially at risk as well. Rises in rivers, creeks and streams will
result in minor river flooding at least. Risk of runoff continues to
grow as additional rounds of rainfall saturate soils. Once again,
Moderate Rainfall Risks are seldom issued, only when there is
strong confidence that significant, life-threatening flash flooding
could occur. Around 1 out of 5 fatalities from flooding occur on a
Moderate risk days. A Flood Watch remains in effect for all of SE
Texas until Thursday morning. Make sure to have multiple ways of
receiving warnings and remain weather aware! Do not attempt to drive
through flooded roadways. TURN AROUND, DONT DROWN!

In addition to rainfall, we will also have to watch out for many
other tropical-related hazards with this low pressure. Strong winds
will be possible as this system moves across the region. However,
there is still a wide amount of spread between models, with winds
highly contingent on the strength of the low and whether tropical
development occurs or not. Right now, we're anticipating the
strongest winds to occur along the coast, especially over the bays
and Gulf waters. These winds could reach 20-30 knots with gusts to
Gale. Timing the onset of these winds is extremely difficult given
the large timing differences, though model guidance shows the most
intense winds occuring generally between 4AM to 4PM on Wednesday.

With the tropical airmass and the potential for tropical
development, SPC also has included a Marginal Risk (level 1/5) SWO
over portions of the SE Texas coast through early Thursday morning.
Tropical funnels and waterspouts could develop over the waters...
could potentially see some of this activity move over land too
(contingent on tropical development of course).

Strong currents are expected, with minor coastal flooding possible
on Wednesday and Thursday and high tide. A moderate to high risk of
rip currents is expected for Gulf-facing beaches as well.

The heavy rainfall threat should decline on Thursday, though a
Slight (level 2/4) Risk of Excessive Rainfall will still be in place
for lingering rains as the system departs eastward. This risk will
diminish into Friday with rain chances decreasing into the weekend
as ridging builds over the Gulf.

03

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 626 PM CDT Mon Jun 15 2026

Lingering showers are expected to gradually dissipate this
evening. Tomorrow, scattered to numerous SHRA/TSRA will persist
throughout the day. The next round of heavier rain is expected
move northward into the area in the early morning. Another round
of heavy rain is likely starting in the early afternoon. Expect
-SHRA/TSRA throughout the day tomorrow. The main impacts for
terminals will be lightning, low CIGS, and low VIS associated with
these thunderstorms. An IFR/MVFR cloud deck is expected to move
in from the northeast, causing low CIGS at most terminals starting
early tomorrow morning, and lasting until the early evening. CIGS
should lift to low end VFR by late afternoon, though MVFR CIGS
may stick around especially near the coast.

&&

.MARINE...
Issued at 1154 PM CDT Mon Jun 15 2026

Additional rounds of widespread showers/storms are expected through
the later half of the work week. Light to occasionally moderate
onshore winds and seas of 3 to 6 feet are expected to increase
tonight into Wednesday as a low moves into the northwestern Gulf.
Moderate to strong onshore winds may develop as this system tracks
through the waters. While there is a large difference in timing
between models, the most intense winds are generally anticipated to
occur some time between 4AM to 4PM on Wednesday. Intensity is
contingent on tropical development, though winds around 20-30 knots
with gusts to Gale will be possible. Seas could reach 7-10 feet,
potentially higher at times. Tropical funnels and waterspouts could
develop as well. Strong currents are expected. Minor coastal
flooding is possible on Wednesday and Thursday around high tide. A
moderate to high risk of rip currents is expected for Gulf-facing
beaches as well.

Sustained winds should drop under 25 knots around Thursday
afternoon, though seas will remain slightly elevated, only dropping
below 6 ft by around Friday afternoon/evening.

03

&&

.TROPICAL...
Issued at 1154 PM CDT Mon Jun 15 2026

A trough of low pressure currently over the eastern Texas/Mexico
boarder is expected to drift north-northeastward throughout today.
Spaghetti plots for Invest 90L all support this motion, with the
system favored to move into northwestern Gulf along the Texas coast
today. Once over the waters, this low could deepen and potentially
organize into a tropical storm. Convection within this low has
flared up overnight, showing more promising signs of TC development.
With this in mind, NHC now gives this system a 60% chance of
tropical development within the next 48 hours. Regardless of
tropical development, heavy rainfall is expected and dangerous
marine conditions are possible. Rainfall rates are expected to be
around 2-5"/hr, possibly higher, especially along the coast.
Moderate to strong winds could develop across the waters and bays
early Wednesday with gusts to gale. Tropical funnels and waterspouts
could spin up at times throughout Wednesday. Minor coastal flooding
could occur as well.

03

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)	  82  73  84  73 /  90  60  50  10
Houston (IAH)			  83  75  82  75 /  90  80  90  40
Galveston (GLS)			  88  80  85  80 /  50  90 100  80

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through Thursday morning for TXZ163-164-176>179-
     195>200-210>214-226-227-235>238-300-313-335>338-436>439.

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

&&

DISCUSSION...03
AVIATION...MLG
MARINE...03
TROPICAL...03