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National Weather Service Forecast Discussion

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477
FXUS64 KHGX 192038
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
338 PM CDT Tue May 19 2026

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

.KEY MESSAGES...

- Multiple rounds of thunderstorms are expected this week with
  the first round arriving tonight. Strong to severe storms will
  be possible with damaging winds as the main threat. Locally
  heavy rainfall also expected.

- Rain and storm chances remain elevated through the entire
  holiday weekend with periods of locally moderate to heavy rain,
  potentially leading to localized flooding.

- The threat of hazardous rip currents remains through at least
  midweek before marine hazards transition to thunderstorm-driven
  waves.

&&

.DISCUSSION...
Issued at 305 PM CDT Tue May 19 2026

Wetter conditions are expected this week and into Memorial Day
weekend with multiple rounds of moderate to heavy rain.

Synoptically speaking, a broad longwave trough will continue to
deepen and move across the Rockies and into the Plains today,
persisting through the rest of the week. With a persistent
southwesterly flow aloft, this trough is helping to eject multiple
impulses of energy/disturbances ahead of it, resulting in increased
dynamics/forcing across the region. At the surface, a warm and very
moist airmass (PWAT near/at the climatological max for mid-May)
along with an approaching frontal boundary from the north, will
be enough to support a daily risk of showers and storms.

This afternoon/early evening: A warm and humid airmass remains in
place over the region. With moderate instability, and weak boundary
(-ies) meandering over the area; we expect to see isolated to
scattered activity.

Tonight into Wednesday: The first round of scattered to widespread
showers and storms is expected as early as this evening, continuing
into early Wednesday. Early this afternoon, satellite and surface
obs showed a cold front slowly moving southeast into north-central
TX. While this front is forecast to remain to our west, a fairly
unstable warm and moist airmass ahead of it, combined with deep
moisture convergence due to a developing surface trough, and forcing
aloft could potentially lead to scattered to widespread showers and
thunderstorms. We will continue to monitor these clusters of storms
as they could potentially evolve into a line of bowing segments,
capable of producing damaging winds. SPC highlights this threat in
their Day 1 Outlook with a slight risk (level 2 of 5) of severe
weather across our far western counties, and a marginal risk (level
1 of 5) elsewhere. In addition to strong to severe storms, locally
moderate to heavy rain is expected with the strongest storms.
Forecast rainfall amounts of 1 to 3 inches can be expected with
isolated higher amounts of 5 to 7 inches possible. Rainfall rates of
2 to 4 inches per hour will likely leading to localized flash
flooding along with quick responses on area rivers and creeks.
Rain/storms should gradually taper off early Wednesday morning.
While a lull in activity is possible during the day, cannot ruled
out isolated to scattered showers/storms popping up in the
afternoon with the peak of daytime heating.

Thursday and Friday: Periods of showers and storms will continue as
more disturbances aloft move through the region. The next mesoscale
convective system is forecast to move through on Thursday during the
day, with an additional isolated to scattered activity on Friday.
Specific details on the exact timing and location of the heaviest
rain remain difficult to determine; however, widespread rainfall
totals of 1 to 2 inches will be possible with isolated higher
amounts up to 4 inches possible.

Memorial Day Weekend ( Saturday - Monday): A continuos parade of
disturbances aloft combined with sufficient deep moisture will
support additional periods of showers and storms through the entire
holiday weekend. Based on the latest trends, forecast rainfall
totals of 4 to 6 inches are possible. Locally higher totals
possible,especially with the strongest storms. With the ground
already saturated from previous rainfall, soils will be primed for
runoff, leading to flooding problems in areas of heavy downpours.
While confidence is high for a wet weekend, confidence in the
exact timing and location of the heaviest rain is low. Initial
rounds of storms early in the week will potentially affect any
storms later in the week. Focus on the potential impacts and stay
tuned to the latest forecast, especially if you have outdoor plans
this Memorial Day weekend.

See Hydrology section below for more information on forecast
rainfall and potential flooding.

JM

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 627 AM CDT Tue May 19 2026

SHRA and isolated TSRA over the area will dissipate over the next
few hours. MVFR cigs expected to trend VFR by the afternoon, with
SE winds becoming more ESE later in the day. We still anticipate a
line of SHRA/TSRA to move into the area from the north and west
this evening / overnight. However, confidence in the forecast
(especially regarding TSRA timing and severity) is quite low. In
addition, the wind direction/speed forecast is uncertain tonight
into Wednesday morning. The primary concern from TSRA will be
strong gusty winds.

&&

.MARINE...
Issued at 305 PM CDT Tue May 19 2026


Winds and seas will continue to weaken/subside this afternoon, with
only some building seas up to 8ft persisting well offshore through
early this evening. Multiple rounds of showers and thunderstorms are
expected this week, with the first one starting tonight and
extending into early Wednesday morning. A few of these storms will
be capable of becoming strong to severe with strong winds as the
main threat. Locally heavy rain will also be expected. A daily risk
of showers and storms will continue this week and persist through
the Memorial Day weekend. Light to occasionally onshore winds should
prevail through the period; however, stronger gusts are possible in
the vicinity of thunderstorms. Regarding beach conditions, there is
a high risk of rip currents persisting through the weekend.

JM


&&

.HYDROLOGY...
Issued at 305 PM CDT Tue May 19 2026

Multiple rounds of moderate to heavy rainfall are expected this
evening through Monday. The first round will start tonight bringing
1-3" with isolated higher amounts of 5-7+". With PW values exceeding
the 90th percentile (~1.7-2.1"), rainfall rates of 2-4"/hr are
possible in the heaviest downpours. Anywhere we see these intense
rainfall rates, localized flash flooding is possible. That being
said, we are not anticipating widespread river flooding just yet;
however, this will help prime the soils as we continue with a wet
pattern.

As the week progresses, multiple rounds of moderate to heavy
rainfall on top of primed soils will generate runoff and cause rises
on area rivers and watersheds. The greatest threat for heavy
rainfall, flash and riverine flooding comes this holiday weekend as
intense rainfall rates will bring accumulated values of 4-6+" across
most of southeast Texas Saturday into Monday.

Widespread action to minor stage flooding is expected with moderate
to isolated major stage flooding possible 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)  69  83  70  80 /  70  50  40 100
Houston (IAH)  71  86  73  84 /  70  60  30 100
Galveston (GLS)  75  85  78  85 /  70  60  10  70

&&

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

GM...Small Craft Advisory until 7 PM CDT this evening for GMZ370-375.

&&

$$

DISCUSSION...JM
AVIATION...Self
MARINE...JM
HYDRO... Landry-Guyton

NWS HGX Office Area Forecast Discussion