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National Weather Service Forecast Discussion

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869
FXUS64 KHGX 181047
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
547 AM CDT Mon May 18 2026

...New AVIATION...

.KEY MESSAGES...

- Warm, breezy, and muggy conditions will continue for the next
  several days.

- Isolated showers/storms possible overnight, isolated to
  scattered showers/storms on Monday, followed by increasing
  chances of showers and storms for the rest of the week.

- Multiple rounds of showers/storms expected beginning late
  Tuesday through the end of the work week. A few storms could be
  strong to severe and multiple rounds of rainfall could lead to
  minor/street flooding.

- Elevated winds, seas, tides, and rip current risk in the
  bay/Gulf waters and beaches through at least midweek.

&&

.DISCUSSION...
Issued at 1212 AM CDT Mon May 18 2026

I`m gonna go ahead and lead in with the main takeaways for this
discussion: have an umbrella/poncho with you throughout the week,
remain weather aware by staying up to date on the latest forecasts,
and have multiple ways to receive alerts of impactful weather.
That`s your big three for this week.

A band of showers is setting up over Central Texas and is gradually
pushing into Southeast Texas this evening. PW values remain well
above the 90th percentile (~1.79") and when you pair that with a
strengthening LLJ (30-40 kt) and embedded shortwaves, you get
*vaguely gestures at radar reflectivity* that. Some of the latest
00Z CAM guidance indicates the potential for isolated embedded
thunderstorms overnight as well. Based on the instability and
lifting mechanism in place (the LLJ), this is an entirely plausible
outcome (and not only because it`s already occuring). This is most
likely to occur near or north of I-10 during the overnight hours, so
don`t be surprised if you wake up before your alarm to some rumbles
of thunder...Happy Monday! Monday will feature isolated to scattered
showers with a non-zero chance of an isolated storm or two in the
afternoon mainly north of I-10. Outside of the rain chances, it`s
gonna be warm and muggy. High temperatures will continue to top out
in the upper 80s to low 90s with heat index values peaking in the
upper 90s/low 100s. A rinse and repeat for Tuesday, but definitely
more so on the rinse part of that as we head into late Tuesday.

The wet pattern that we`re moving into Tuesday and beyond is
courtesy of a longwave trough that is becoming established over the
western CONUS. Southwesterly flow aloft will lead to embedded
shortwaves passing through the area with the first notable one being
on late Tuesday. Exact timing is still uncertain (as always when
trying to time shortwaves), but we`re currently looking at Tuesday
evening for the first round of showers/storms. This shortwave is
expected to result in a line of showers/storms, or if you want to be
fancy you can call it a Mesoscale Convective System (MCS) that
pushes into the area on Tuesday evening. A few of these storms could
be strong to severe and be capable of producing strong wind gusts
and hail. As a result, majority of Southeast Texas is outlined in a
marginal risk (level 1 of 5) of severe weather on Tuesday. The
severe weather outlook may change with the overnight update, so be
sure to stay tuned to the forecast. The line of storms is visible at
the very end of 00Z CAMs and we can see convection beginning to
approach the Brazos Valley right around 7pm Tuesday evening.

Additional rounds of showers and thunderstorms are anticipated
throughout the week with the most likely mechanism being more MCS`s
especially along a nearby frontal boundary that makes its closest
approach around midweek. Where this boundary lingers/stalls will be
key to who gets the most amount of rainfall this week. With PW
values remaining near or above the 90th percentile, locally heavy
rainfall will be possible. There is additional details down below in
the Hydrology section. A brief summary of it is, the rounds of rain
earlier in the week will help to prime the soils. This means that
rounds of rain later in the week could result in a quicker
transition to runoff which increases the potential for minor/street
flooding. We`ve already seen in recent events over the past few
weeks that PW values in this range can result in 3-4+"/hr rainfall
rates in the heaviest downpours.

As a result, all of Southeast Texas is outlined in a marginal
risk (level 1 of 4) Tuesday through at least Thursday. I say at
least because with rain chances sticking around into the weekend,
there is decent potential that at least portions of the area will
remain outlined in the Excessive Rainfall Outlook. Speaking of
Thursday, a portion of the Brazos Valley is outlined in a slight
risk (level 2 of 4) of excessive rainfall on Thursday. Training
convection along the lingering frontal boundary cannot be ruled
out. Be sure to stay tuned to the forecast for the latest details.

As far as rainfall totals go, we continue to anticipate widespread
totals of 2-4" with isolated amounts of 4-6+". This is for the
Tuesday through Friday timeframe, and those higher end amounts are
still most likely to occur north of I-10. The frontal boundary
continues to linger going into the weekend alongside a steady dose
of passing shortwaves and elevated PW values, so chances for
showers/storms continue going into the weekend. With daily chances
for moderate to heavy rainfall, we`ll be keeping an eye on area
rivers/streams...that`s another hint to check out the Hydrology
section below.

In case you wanted to know more about the temperature forecast,
there`s a downward trend going into midweek with the increasing rain
chances (surprise surprise). We go from high temperatures in the
upper 80s/low 90s on Monday and Tuesday to the low to mid 80s
midweek and beyond. The temperature forecast will likely change
based on timing and location of these rounds of showers/storms. I(
can mention though that we`ll at least flirt with record high
minimum temperatures early this week with low temperatures only
bottoming out in the upper 70s/low 80s. Yeah...some of y`all might
not drop below 80 overnight. Now that`s what I call humid!

Batiste

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 543 AM CDT Mon May 18 2026

Widespread MVFR cigs should generally trend VFR this morning.
Coastal areas may struggle break out of MVFR cigs, but perhaps a
brief period of VFR could occur this afternoon like yesterday.
Winds will continue to be gusty and out of the southeast.
Sustained winds are expected to average in the 15-20 knot range,
with gusts over 25 knots expected in some areas. Cigs should trend
back to MVFR by evening and overnight.

&&

.MARINE...
Issued at 1212 AM CDT Mon May 18 2026

Small Craft Advisories remain in effect through Tuesday morning as
moderate onshore winds and elevated seas continue to persist. Winds
and seas gradually subside on Tuesday. Multiple rounds of showers
and thunderstorms are anticipated beginning late Tuesday through at
least the end of the work week. Some of these storms could produce
strong wind gusts, especially if they push offshore in the form of a
line of storms. Outside of the storms, onshore winds will persist
generally in the 10-15 kt range after Tuesday.

The other topic of interest for mariners is the continued high risk
of rip currents and potential for minor coastal flooding during
times of high tide. Water levels at Galveston Bay Entrance reached
3.3 ft MLLW during high tide on Sunday morning. P-ETSS guidance
continues to indicate water levels being slightly higher than that
during high tide Monday morning peaking closer to 3.5 ft MLLW. Water
levels during high tide on Tuesday morning are currently expected to
peak just above 3.0 ft MLLW. A Beach Hazards Statement remains in
effect through Monday morning and will transition to a Rip Current
Statement afterwards through Tuesday evening (for now). Expect the
rip current risk to remain high through at least midweek.

Batiste

&&

.HYDROLOGY...
Issued at 1212 AM CDT Mon May 18 2026

Anticipating multiple rounds of moderate to heavy rainfall Tuesday
through at least Friday. These rounds are expected to mostly be in
the form of Mesoscale Convective Systems (MCS`s). The exact timing
of these storms can be a bit tricky as mesoscale factors play a key
role (hence the name), but we anticipate the first round to come
late Tuesday. With PW values near or above the 90th percentile
(~1.79"), rainfall rates will likely exceed 3-4"/hr in the heaviest
downpours. While these lines of storms are typically progressive,
the rainfall received early in the week is expected to prime the
soils for rounds later in the week. Saturated soils leads to a
quicker transition to runoff which brings an increased risk of
minor/street flooding. We continue to anticipate widespread rainfall
totals of 2-4" with isolated higher amounts (4-6+" possible). The
highest rainfall totals are still expected to occur north of I-10.

This rainfall will generate runoff and cause rises on area rivers
and watersheds. Action to minor stage flooding is the most likely
outcome, but cannot entirely rule out isolated instances of moderate
stage flooding depending on where the most rainfall accumulates.
Remember that you can monitor updated river forecasts via the NWS
NWPS webpage (https://water.noaa.gov/).

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  90  78  89  72 /  10  20  60  70
Houston (IAH)  89  79  89  75 /  20  10  40  70
Galveston (GLS)  86  81  86  79 /  20  10  20  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Beach Hazards Statement until 10 AM CDT this morning for
     TXZ436>439.

     High Rip Current Risk from 10 AM CDT this morning through
     Tuesday evening for TXZ436>439.

GM...Small Craft Advisory until 9 AM CDT Tuesday for GMZ330-335-350-
     355-370-375.

&&

$$

DISCUSSION...Batiste
AVIATION...Self
MARINE...Batiste

NWS HGX Office Area Forecast Discussion