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National Weather Service Forecast Discussion

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051
FXUS64 KHGX 201131
AFDHGX

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

...New AVIATION...

.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 impact 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 diurnally 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 widespread 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...
(12Z TAF Issuance)
Issued at 600 AM CDT Wed May 20 2026

Showers and thunderstorms are ongoing this morning, and continue
to move east/southeast across the CWA. Based on the most recent
model guidance, storms are expected to move southeast and exit the
region by about 16Z. All sites prevail at VFR, with the main
concern being the showers and thunderstorms ongoing this morning.
Early this afternoon, CIGs are forecast to lower to MVFR for a
brief period, before returning to VFR mid-afternoon. Winds will
be about 5-10 KTs and variable today as the storms move through,
eventually becoming southeasterly this afternoon. Near the end of
this TAF period, another round of showers is expected to move in
from west to east, although timing and the associated CIGs are
uncertain. CIGs should lower, though it is uncertain whether they
will lower enough to transition from VFR to MVFR. We will monitor
trends in case amendments are needed.


&&

.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.

&&

$$

DISCUSSION...47
AVIATION...MLG
MARINE...47

NWS HGX Office Area Forecast Discussion