Skip to main content.

National Weather Service Forecast Discussion

Related quick links> 5 Day Forecast, Local Advisories, Drought Monitor, UV Forecast, Air Quality Forecast 
650
FXUS64 KHGX 211117
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
617 AM CDT Thu May 21 2026

...New AVIATION...

.KEY MESSAGES...

- The next upper level disturbance will be moving into the area
  from the west early this morning and across the area into early
  afternoon. A Flood Watch will remain in effect for counties
  along the coast through Monday morning.

- Multiple rounds of thunderstorms are expected through the
  holiday weekend and into next week. Some may be strong at
  times. Locally heavy rainfall is possible 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 111 AM CDT Thu May 21 2026

Satellite imagery shows 2 areas of interest early this morning.
An upper disturbance, and a few embedded stronger tstms, is
pushing into the Hill Country. It`s situated along a weak surface
boundary and some modest upper diffluence aloft which is probably
maintaining the stronger cells on its southern periphery. SPC
mesoanalysis indicates this precipitation will be moving into a
more stable airmass as it nears the Brazos Valley. So, assuming no
substantial surprises between now and then...we`d generally
anticipate some weakening as it approaches the local area.

The second area of concern is the disturbance moving into South
Texas from Mexico. Guidance all generally agrees storms associated
with this one should maintain themselves as they move into a more
unstable environment. The uncertainty lies in the finer
details...whether it mostly stays offshore...or, as some of the
00z hires models (NSSL, ARW, FV3, RRFS) suggest - taking an MCV on
a bit of a more ENE route and up the upper Tx coast. I don`t have
a great feel on how this one evolves, but if the stronger
northern route takes shape this batch of storms may make it to the
Matagorda Bay area around or shortly before sunrise then track NE
across the remainder of the area during the day. A Flood Watch
remains in effect for coastal regions from last nights heavy rain.
Additional heavy rain in a short period will be prone to quickly
runoff and produce some flooding. If the southern trajectory ends
up being the way it decides to go, expect less overall coverage
across the region and lesser amounts. There is a weak pseudo
coastal trof/boundary near the coast leftover from last nights
convection to watch for some focusing.

Otherwise, not much to add that hasn`t already been said. Pattern
will be favFM220600 VRB05KT P6SM BKN025orable for additional
rounds of showers and tstms...especially this weekend (and quite
possibly into a good part of next week) as the western mid-upper
trof and associated disturbances slowly track toward and into
Texas then put on the brakes for several days. It`s not a good
pattern to be in this time of year and appears to be a somewhat
prolonged favorable heavy rain setup for this region. Though
confidence on the overall pattern/rain chances is above
average...confidence in regards to specific timing and rain
amounts are fairly low. With each additional bout of rain, the
soils will become increasingly saturated and have less ability to
absorb the precipitation...and the corresponding risk of
flooding/flash flooding will increase. When deterministic data
points at an additional 4-6" by midweek, we all know some isolated
locations can receive much higher amounts, in a much shorter
amount of time, this time of year. Residents should keep up with
the latest weather forecasts. 47

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 612 AM CDT Thu May 21 2026

Heavy SHRA/TSRA over S TX may extend as far north as our coastal
zones this morning, potentially impacting GLS and LBX. For the
Houston area, we expect some SHRA this morning, with the best
chance of steadier rainfall south of I-10. The afternoon forecast
is highly uncertain. May see some diurnal SHRA/TSRA activity
early afternoon, as well as late afternoon/early evening near a
stalled boundary to our north (more applicable to CLL and UTS).
The next disturbance may not arrive until tomorrow morning. It is
uncertain as to whether or not it will bring widespread SHRA/TSRA
or be limited to southern / coastal areas like this morning.

&&

.MARINE...
Issued at 111 AM CDT Thu May 21 2026

The next weather disturbance will be pushing off the mid and lower
Texas coast overnight. The northern periphery of this storm complex
could track across portions of the upper Texas coast between
about 5am and noon, though timing of storms remains a bit
uncertain. Mariners should check the latest forecast and weather
conditions before beginning or continuing their transits. Multiple
rounds of showers and thunderstorms are anticipated through the
holiday weekend, so take note of the potential for intermittent
periods of elevated winds and seas in and around any of the
stronger thunderstorms. Outside of the storm complexes, expect
light to occasionally moderate onshore flow with 3-5 ft seas. 47

&&

.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)  80  69  85  71 /  60  30  40  20
Houston (IAH)  80  71  86  74 /  80  40  60  20
Galveston (GLS)  81  77  83  78 /  80  30  60  20

&&

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

GM...None.
&&

$$

DISCUSSION...47
AVIATION...Self
MARINE...47

NWS HGX Office Area Forecast Discussion