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National Weather Service Forecast Discussion

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975
FXUS64 KHGX 220632
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
132 AM CDT Fri May 22 2026

...New DISCUSSION, MARINE...

.KEY MESSAGES...

- A Flood Watch remains 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 1136 PM CDT Thu May 21 2026

An active weather pattern is expected to prevail through next
week as several mid to upper level disturbances pass through TX.
For tonight through Friday morning, although some isolated spots
could see a light shower or two, we are expecting it to remain
mainly warm and humid. During the mid/late morning to the
afternoon hours on Friday, we are expecting to have shower and
thunderstorm activity increase from the coasts and expand
northward as diurnal heating peaks, instability increases and a
few vort maxes pass through. Speaking of heat, it will remain
rather humid on Friday with highs in the mid to upper 80s and heat
indices in the lower to mid 90s. Rain activity will decrease
Friday evening as we loose the diurnal heating. There will be
storms developing to our north, thus, we will need to keep an eye
for the possibility of these storms rolling into the Brazos Valley
and Piney Woods region.

Conditions are expected to get more active Saturday into Sunday.
This is due to an upper level trough moving across TX that is to
combine with PWs of near 2.0 inches, a saturated profile from the
surface through the mid levels, the passage of multiple vort
maxes, and CAPE values of 2-3K J/kg. This will lead to several
rounds of showers and thunderstorms through much of the day and
night. In addition to the locally developed activity, we might
have the storms that developed to our north and west roll in,
which can account for higher rain chances. For this forecast
issuance, we have continued to carry numerous to widespread
showers and thunderstorms Saturday morning into Sunday morning.
With the amount of moisture that is to be in place, it will be of
no surprise for moderate to heavy rainfall to develop (some
showers could even produce rainfall rates of 2-4" per hour). Given
that soils are fairly saturated from the rains we have received
over the last few days, it will not take much for heavy rainfall
to cause runoff and/or flooding impacts - in particular over the
coastal areas. For that reason, a Flood Watch will continue in
effect through Monday. The Watch is currently for most counties
south of I-10 and west of I-45, however, it may be expanded based
on where these heavy rains set up. WPC continues a Slight Risk
(level 2 of 4) for all of Southeast TX valid from 7 AM Saturday
through 7 AM Sunday. Some locations may be upgraded to a Moderate
Risk (level 3 of 4) later today.

The environment will remain favorable for additional showers and
thunderstorms on Sunday as another upper level trough pushes
across TX. We continue to carry numerous to widespread showers
and thunderstorms, although the heaviest activity could be
situated over areas near and south of I-10 and east of I-45. But
let`s not sleep on that given that the placement of activity could
end up either more north or even over the waters. Unfortunately,
the Hi-Res models have not been performing too well lately. From
7 AM Sunday through 7 AM Monday, the Slight Risk will continue
over locations near and east of Galveston Bay and a Marginal Risk
(level 1 of 4) will cover the rest of Southeast TX. Again, because
there is uncertainty of the exact location of the heavy showers,
please make sure to monitor the radar and latest forecast updates
and have multiple ways of receiving weather warnings. Make sure to
check the traffic conditions before departing and never cross
flooded roads.

Slightly lower chance for rain is expected Monday (Memorial Day)
as the air dries a bit. However, we might have a few vort maxes
still making their way through and sufficient instability for
scattered showers and thunderstorms. Even if the potential for
heavy rainfall ends up being less, even moderate rain can lead to
minor flooding impacts over those areas affected by heavy rainfall
from Saturday and Sunday.

Unfortunately, we are likely looking at rain chances each day
through the rest of the work week as the "trough pattern" prevails
aloft. Not sure if we will get a good day to cut our front yard
forest :/

Stay tuned for more.

Cotto

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 607 PM CDT Thu May 21 2026

A few lingering late day cells leftover from the shortwave that
passed through earlier today should be waning early this evening
for most of the area. However, we`re watching another shortwave
and associated storms in the Hill Country that could pivot into
the CLL/UTS area this evening. Overall intensity trend should be
declining with time...but we`ll keep an eye on things. Otherwise,
mainly VFR and dry for the rest of the region during the overnight
period. With light winds, wet ground, and thinner cloud cover I
wouldn`t be surprised to see some patchy late night fog
development across parts of the area. Next fairly weak shortwave
and remnant light precip coming out of Mexico should make it into
our southern terminal (IAH southward) in the 14-18z timeframe Fri.
Unsure on overall coverage so have some PROB30s in the TAFs for
now. Rest of Friday appears primarily uneventful outside of some
iso-sct tstm pop-ups associated with afternoon heating. 47

&&

.MARINE...
Issued at 1136 PM CDT Thu May 21 2026

Light south to southeast winds with seas of 2-4 feet are expected
through early next week. Multiple rounds of showers and
thunderstorms are expected for the next several days and although
there currently isn`t a severe threat, elevated winds and seas
may still occur in and around strong thunderstorms.

Cotto

&&

.HYDROLOGY...
Issued at 143 PM CDT Thu May 21 2026

Multiple rounds of moderate to heavy rainfall are expected through
at least Monday. Areas along the coast, especially Matagorda and
Brazoria Counties, received 5-8" over the past 48ish hours. The next
round of rain is expected to move in either late this evening or
Friday morning. Some of this rainfall may occur along the coast,
which brings the potential for flash flooding. As a result, a Flood
Watch continues for coastal counties through Monday morning. The
Flood Watch will likely be extended northward and eastward within
the next 24 hours to cover the threat area for the Saturday into
Sunday timeframe of concern.

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. 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 we go into the weekend, 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 over the holiday weekend
as intense rainfall rates will bring accumulated values of 4-6+"
across most of Southeast Texas through 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)  69  85  71  82 /  60  30  20  80
Houston (IAH)  70  87  74  84 /  40  50  20  80
Galveston (GLS)  75  85  79  85 /  30  30  10  60

&&

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

GM...None.
&&

$$

DISCUSSION...Cotto
AVIATION...47
MARINE...Cotto

NWS HGX Office Area Forecast Discussion