Skip to main content.

National Weather Service Forecast Discussion

Related quick links> 5 Day Forecast, Local Advisories, Drought Monitor, UV Forecast, Air Quality Forecast 
781
FXUS64 KHGX 201930
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
230 PM CDT Wed May 20 2026

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

.KEY MESSAGES...

- A Flood Watch will go into effect for counties along the coast
  Thursday morning through Monday morning.

- Multiple rounds of thunderstorms are expected through the
  weekend. Some may be strong at times. Locally heavy rainfall is
  expected at times leading to the potential of flash flooding.

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

&&

.DISCUSSION...
Issued at 230 PM CDT Wed May 20 2026

With the threat for additional rounds of moderate to heavy rainfall
going into the holiday weekend, there are naturally a lot more eyes
on the forecast. With that in mind, I`ll be tailoring this
discussion mainly to what`s expected and what are the potential
impacts as a result of that...so I`ll try not to use any complicated
weather jargon this time around. Your main takeaways should be to
stay weather aware by keeping up with the latest forecasts and have
multiple ways to receive alerts (especially if you plans to be out
on the road for the holiday weekend). Let`s begin.

There were two rounds of showers/storms between Tuesday evening and
Wednesday morning resulting in 3-6+" of rainfall along the coast
(especially in Matagorda and Brazoria Counties). High-res model
guidance is mostly in consensus on the next round of showers and
storms moving through Thursday morning mostly along the coast. This
rain is expected to move over areas that received the bulk of the
rainfall last night/this morning. As a result, we decided to move
forward with issuing a Flood Watch that extends from Thursday
morning to Monday morning for counties along the coast. For
additional details on the Flood Watch, see the Hydrology section
below.

The good news is the remainder of the day today is anticipated to be
on the dry side. That being said, we are starting to see some breaks
in the clouds out to the west so can`t entirely rule out some
isolated to scattered showers/storms later this afternoon. The
latest HRRR does show some spotty convective activity within the
next few hours near and south of I-10. As we talked about above, the
next round of the more widespread variety of showers/storms is
"expected" to be Thursday morning. I included parentheses because
timing these shortwaves (disturbances) can be tricky as we saw last
night. High resolution model guidance shows the most of this
rainfall occuring along the coast. There remains some uncertainty on
the timing of shortwaves (disturbances) beyond that, but we are
anticipating that they`ll keep pushing into the area with an upper
level low gradually approaching from the west going into the
weekend. We`ll have to monitor the progression of this upper low as
it moves into Southeast Texas early next week (potentially moving
overhead by Monday/Memorial Day). PW values will remain near or
above the 90th percentile (~1.79") into early next week, so moisture
availability will not be an issue in the slightest. Some of these
storms may be strong at times carrying the potential for strong
winds.

With all of that in mind, there is daily potential for locally heavy
rainfall. We ended up creating a four panel Excessive Rainfall
Outlook graphic to give y`all an idea of how long the heavy rain
threat extends for...and that`s not even including Day 5 (Sunday).
This will likely extend into Monday/Memorial Day as well, so just
know that we alternate between a marginal risk (level 1 of 4) and a
slight risk (level 2 of 4) each day going into the weekend, but this
is subject to change once we gain confidence on timing/location of
the heavy rainfall potential. As far as rainfall totals go, we`re
anticipating widespread amounts of 4-6" with isolated higher amounts
for Thursday-Monday. Keep in mind that these initial rounds of
rainfall are priming the soils for the later rounds of rainfall.
Saturated soils lead to quicker runoff, which brings the potential
for flash flooding (hence the Flood Watch issuance). There is
potential for the Flood Watch to be expanded in area going into the
weekend, so be sure to stay up to date on the forecast for the
latest details.

In case you wanted to know about the temperature forecast, it`s
going to be highly dependent on the timing of these rounds of rain.
For now, we have high temperatures mainly in the low to mid 80s
through next week but there may be times where the high temperatures
remain in the 70s depending on timing of rainfall. Low temperatures
will mostly be in the upper 60s to low 70s.

Batiste

&&

.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 230 PM CDT Wed May 20 2026

Multiple rounds of showers and thunderstorms are anticipated through
the holiday weekend, so mariners should take note for the potential
for intermittent periods of elevated winds and seas in and around
any of the stronger thunderstorms that push through the waters. The
next round of showers and thunderstorms is expected on Thursday
morning. Timing of storms beyond that is a bit uncertain, but
additional rounds are expected into at least Monday. Outside of the
storms, expect light to occasionally moderate onshore flow with 3-5
ft seas.

Batiste

&&

.HYDROLOGY...
Issued at 230 PM CDT Wed May 20 2026

Multiple rounds of moderate to heavy rainfall are expected through
at least Monday. Areas along the coast, especially Matagorda and
Brazoria Counties, received 4-6+" between the rounds of rainfall
Tuesday night into Wednesday morning. These areas are expected to
see another round of moderate to heavy rainfall on Thursday and
Friday, which brings the potential for flash flooding. As a result,
a Flood Watch was issued for coastal counties for Thursday morning
through Monday morning. The current extent of this Flood Watch
includes areas with a flood threat within the next 24-48 hours, so
the watch could be expanded in area as the rainfall threat evolves
going into the weekend. With PW values near or above the 90th
percentile (~1.79") through the weekend, rainfall rates are expected
to peak in the 3-4+" per hour range in the heaviest downpours.
Additional rainfall totals through Friday are anticipated to be in
the 2-4" range along the coast. Through Monday/Memorial Day,
expecting widespread 4-6" rainfall totals with isolated higher
amounts.

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 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/).

Batiste/Landry-Guyton

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  70  79  70  83 /  40  80  50  50
Houston (IAH)  72  81  72  85 /  20  70  60  80
Galveston (GLS)  77  82  77  85 /  10  70  70  70

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch from Thursday morning through Monday morning for
     TXZ226-227-235>238-335>338-436>438.

     High Rip Current Risk through Thursday evening for TXZ436>439.

GM...None.

&&

$$

DISCUSSION...Batiste
AVIATION...MLG
MARINE...Batiste

NWS HGX Office Area Forecast Discussion