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National Weather Service Forecast Discussion

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112
FXUS64 KHGX 182050
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
350 PM CDT Mon May 18 2026

...New DISCUSSION, MARINE, HYDROLOGY...

.KEY MESSAGES...

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

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

&&

.DISCUSSION...
Issued at 344 PM CDT Mon May 18 2026

BLUF: The weather pattern begins to change this week with multiple
chances for rain and storms continuing well into the Memorial Day
weekend. Localized heavy rain and isolated to scattered strong to
severe thunderstorms will also be possible. Remain weather aware
this week for the latest forecast updates and make sure you have
multiple ways to receive alerts.

A warm and muggy start to the workweek with mostly cloudy skies and
breezy southerly winds. A few showers and storms will be possible in
the afternoon despite a strong 700:850 mb capping inversion. Strong
moisture transport along with a decent LLJ will be enough to support
this activity this afternoon and evening. A warm and muggy night is
anticipated with lows in the upper 70s to near 80s.

A deep longwave trough deepening over the Rockies will continue to
eject multiple impulses of energy along the southwest flow aloft.
This parade of disturbances will move through Southeast Texas while
at the surface, a frontal boundary will attempt to sag southward
into north-central TX before stalling somewhere between the
Dallas/Fort Worth area and the Brazos Valley region through the end
of the week. Total rainfall amounts will strongly depend on where
this boundary stalls. The first round of showers and thunderstorms
(first round of a series of mesoscale convective systems (MCS`s)) is
forecast to arrive to Southeast TX on Tuesday. Given the nature of
these shortwaves, it is difficult to pin-point specific timing.
Latest hi-res guidance suggests scattered activity in the afternoon,
bringing the first MCS Tuesday evening into Wednesday. Forecast
rainfall amounts during this time frame is expected to be between 1
to 3 inches with isolated higher amounts possible.

Scattered showers and storms will continue on Wednesday before the
next MCS`s arrives early Thursday and additional systems persists
into the weekend. With PWAT values near/at the climatological max
for this time of year, combined with enough forcing and a deep warm
cloud layer, rounds of moderate heavy rainfall will be possible. As
noted in the previous discussion, earlier rainfall this week will
serve to prime the soil. This saturated grounds will lead to a
rapid transition to runoff, especially in areas experiencing
repeated rounds of rain. Under this type of scenario, rainfall
rates of 3 to 4+ in/hr are possible in the heaviest downpours.
Overall, 3 to 6 inches of rain is forecast Thursday through
Sunday, with localized higher amounts possible.

Hazards:

Severe Weather: Thunderstorms could become strong to severe with the
first round of storms Tuesday into Wednesday. There is a Slight risk
of severe weather mainly for our northwestern counties (Brazos
Valley). The main severe weather risk is damaging winds. Hail up to
a quarter sized will also be possible.

Heavy Rainfall:

A Marginal risk of excessive rainfall (level 1 of 4) is expected
most of the week. A slight risk (level 2 of 4) is forecast for
Thursday for portions of the Brazos Valley area.

We will continue to monitor trends as these systems evolve in the
coming days. A Flood Watch may need to be considered later this
week. Stay tuned to the forecast not only through the week but also
through the holiday weekend as this unsettled pattern looks to
remain through early next week.

JM


&&

.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 344 PM CDT Mon May 18 2026

Moderate to strong onshore winds and building seas (5 to 8 ft)
will continue through Tuesday morning. A Small Craft Advisory
remains in effect through mid Tuesday morning. Winds and seas will
gradually weaken/subside by Tuesday afternoon, though gusts
between 15 to 10 knots will continue through the week. Several
disturbances will move across the bays and Gulf waters throughout
the week, resulting in scattered showers and thunderstorms, some
of which may be locally moderate to heavy. Some storms could
become strong Tuesday night into Wednesday with gusts of 30 to 40
mph.

A high rip current risk continues along all Gulf-facing beaches.
Given the persistent onshore flow, this risk will likely continue
through the end of the week.

JM

&&

.HYDROLOGY...
Issued at 344 PM CDT Mon May 18 2026

Anticipating multiple rounds of moderate to heavy rainfall Tuesday
through at least Saturday. 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 exceeding the 90th percentile (~1.7-2.1"),
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
flooding. We continue to anticipate widespread rainfall
totals of 5-7" with isolated higher amounts. 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 moderate to isolated major
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/).

Landry-Guyton

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  77  88  73  83 /  20  30  70  90
Houston (IAH)  78  88  76  86 /  20  20  60  80
Galveston (GLS)  79  86  79  86 /  10  20  50  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk through Tuesday evening for TXZ436>439.

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

&&

$$

DISCUSSION...JM
AVIATION...Self
MARINE...JM

NWS HGX Office Area Forecast Discussion