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National Weather Service Forecast Discussion

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543
FXUS64 KHGX 200636
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
136 AM CDT Wed May 20 2026

...New DISCUSSION, MARINE...

.KEY MESSAGES...

- Multiple rounds of thunderstorms are expected this week. Some may
  be strong at times. Locally heavy rainfall also possible.

- Risk of flooding/flash flooding will need to be monitored, moreso
  later this week/weekend as rain totals begin adding up and the
  ground becomes more saturated.

- Mariners should be prepared for the multiple rounds of storms.
  Winds and seas will be higher in and near storms.

&&

.DISCUSSION...
Issued at 136 AM CDT Wed May 20 2026

First round of storms, one of many to come, is in the process of
working its way through the region. Main inpact from these were
30-50mph gusts and some localized heavy downpours. Totals have
mainly been under an inch, but there`s a few spots that`ve seen
1-4". Expect rainfall to taper off in the morning hours, and we`ll
likely be stabilized for a good while afterwards so have trimmed
POPs back for the remainder of the day.

We will remain in an unsettled wx pattern for several days
ahead...characterized by persistent western troffiness and us
being positioned within a very messy southwesterly flow aloft in
advance. With deep Gulf moisture in place (PW`s 1.7-2.1"), chances
of dirnally driven precip will be in place at a minimum. But
stronger impulses embedded in the flow aloft will likely trigger
more organized storm complexes at times, along with the potential
for some stronger storms & heavier rain rates...which can occur
during the nighttime hours as well. Unfortunately in this type of
pattern, the problem is actually identifying these disturbances
when they`re beyond 12-24 hours out, then adjusting for periods of
stabilization afterwards.

Right now, we`re eyeballing the next next stronger impulse and
associated widerspread precip making its way in from the west
toward Thursday morning. Each round will probably bring somewhere
in the order of 0.5-3.0" rainfall to the area. In the short term,
we should be able to handle another round or maybe two without too
many flood issues, other than the typical localized variety. But
as days wear on, the precip totals begin adding up, and the
ground becomes increasingly saturated...we`ll have be be cognizant
of the potential for increasing flood/flash flood impacts in the
days ahead. Guidance remains wet thru the holiday weekend into
early next week as the western mid-upper trof moves into
Texas...and possibly another trof dropping into about the same
area later next week.

&&

.AVIATION...
(06Z TAF Issuance)
Issued at 1126 PM CDT Tue May 19 2026

Two lines of TSRA are the primary concern tonight. One line is
about to push offshore in the vicinity of Galveston Bay. The other
one is moving east to southeastward from the Brazos Valley. Rain
and storms will likely continue impacting many of our terminals
tonight, until the storms push offshore by morning. Light to
occasionally gusty E to ENE winds expected behind the storms. Near
the coast, there may be a period of strong, gust E to SE winds as
the storms push offshore. Mostly MVFR conditions expected in the
morning, followed by a BKN VFR cloud deck in the afternoon. Next
round of SHRA/TSRA may not arrive until late Wednesday night or
Thursday morning.

&&

.MARINE...
Issued at 136 AM CDT Wed May 20 2026

Showers and thunderstorms are in the process of pushing off the
coast. Some 30 to 40 knot gusts are anticipated along the leading
band of storms as they pass southward. Winds could be chaotic in
terms of speed and direction through mid to late morning
Wednesday with a localized tight pressure gradient in the vicinity
of a MCV. We could see somewhat of a lull in speeds at times in
the coming hours, but quickly increase again for 4 to 8 hours
Wednesday morning. Have broadbrushed a SCA for all waters to take
these factors into account.  Otherwise, an unsettled weather
pattern will persist into the weekend...with additional rounds of
storms likely. Unfortunately, each individual complex will be
difficult to time beyond 12 to 24 hours. During breaks in between
systems, look for light to moderate onshore winds and 3-5 foot
seas.  47

&&

.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)  83  70  79  70 /  30  50  90  60
Houston (IAH)  83  73  82  73 /  30  40  80  50
Galveston (GLS)  84  78  84  79 /  40  30  60  60

&&

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

GM...Small Craft Advisory until 11 AM CDT this morning for GMZ330-350-
     355-370-375.

     Small Craft Advisory until 6 AM CDT early this morning for
     GMZ335.

&&

$$

DISCUSSION...47
AVIATION...Cassel
MARINE...47

NWS HGX Office Area Forecast Discussion