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National Weather Service Forecast Discussion

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349
FXUS64 KHGX 231800
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
100 PM CDT Sat May 23 2026

...New DISCUSSION, MARINE...

.KEY MESSAGES...

- Flood Watch remains in effect for most of SE Texas.

- Scattered to widespread showers and thunderstorms are expected
  this afternoon and evening. Some may be strong at times.
  Locally heavy rainfall is possible leading to the potential of
  flash flooding. Additional intermittent periods of rain/storms
  are anticipated Sunday and Monday for parts of the area.

- Mariners should remain weather aware this holiday weekend. Be prepared
  for higher winds/seas in and near storms and allow yourself
  plenty of extra time to return to shore before hazardous weather
  threatens.

&&

.DISCUSSION...
Issued at 1251 PM CDT Sat May 23 2026

Earlier this morning, a mesoscale convective system moved through,
resulting in moderate to heavy rain and strong winds, especially for
areas roughly along and south of the I-10 corridor. Rainfall totals
of 1 to 2 inches were observed, with some pockets of 2.5 to 3 inches.

Current satellite imagery shows different disturbances over
west/central Texas and Louisiana, intensifying as they progress
eastward early this afternoon. Locally, radar is picking up
thunderstorms developing along an apparent boundary extending
along the coast. While the environment stabilized a bit earlier
this morning; clearing skies, especially to our west, will allow
for destabilization to occur this afternoon as storms to our west
reach our area.

So, the next system we`re keeping an eye on is the one currently
east of the San Antonio area. While hi-res guidance, including the
NAM struggled to initialize this complex this morning, most of them
are in agreement in bringing this system to southeast TX this
afternoon and evening. PWAT values continue to be in the 90th
percentile of climatology. That, combined with increasing low to mid
level instability, upper-level support and deep surface convergence
(boundaries remaining along the coastal counties), will result in
scattered to numerous showers and thunderstorms. Current thinking is
that this complex of storms will be moving east-northeast into the
region this afternoon, mainly focusing along the already mentioned
boundary or boundaries that are extending from Jackson to Chambers
counties. Latest guidance also indicates a strong 700 mb
frontogenesis developing over the region as the main complex moves
through. This scenario shows more instability, and hence higher
rainfall totals possible. In terms of rainfall totals for this
period, an additional 2 to 4 inches can be expected with pockets of
higher amounts of 6+ inches possible through tonight. Rainfall rates
may peak at 3 to 4 inches/hr. Scattered flash flooding will be
possible, especially in areas where have seen repeated storms. In
addition to heavy rainfall, isolated to scattered severe
thunderstorms will be possible, particularly if this complex becomes
into bow segments as they progress east. Damaging winds will be the
primary threat; however hail up to quarter size and a brief isolated
tornado cannot be ruled out.

Showers and storms should begin to diminish in coverage this evening
and overnight. With some boundaries remaining over the region along
with some vort maxes aloft, some isolated to scattered activity
could potentially continue through the night. Another round of
showers and storms can be expected on Sunday; though coverage should
be less as we have seen from previous days. Upper forcing will
generally remain over our eastern half. That, paired with daytime
heating will support activity mainly in the afternoon.

For Monday... convection is again expected as the main upper-lvl low
moves across the southern Plains. Not everyone will see rain during
the day, but again with diurnal heating and "orphan" surface
boundaries meandering over the region; some scattered showers and
storms will be possible. The best chances will be for areas east of
I-45. While forecast rainfall totals have decreased a bit;
a widespread 1 o 2 inches will be possible.

A Flood Watch remains in effect through late Monday.

The rest of the week remains unsettled with periods of showers and
thunderstorms continuing through at least Friday. Periods of
moderate to heavy rain will be possible, particularly over well
saturated soil. Therefore, concerns about isolated to scattered
flooding continue to increase. We`ll have finer details early in the
week as more hi-res guidance comes into agreement. The risk of
excessive rainfall is highlighted in the WPC day 4 and 5 outlooks.

JM

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 604 AM CDT Sat May 23 2026

The unstable airmass over our area ended up winning the night,
with moderate to heavy SHRA/TSRA occurring this morning at many
terminals, especially from IAH to the Gulf. This activity should
exit the area over the next couple of hours. However, more
disturbances will be moving over our region later today into
tonight. Of particular interest is a disturbance over northern
Mexico. Heavy TSRA is approaching the Texas-Mexico border this
morning as a result. This disturbance is expected to enter our
area sometime this afternoon. For now, we have SHRA VCTS
prevailing and TSRA TEMPO groups starting around 20-22 UTC. Some
uncertainty regarding how much TSRA will occur overnight tonight.
If storms the atmosphere stabilizes enough, then overnight TSRA
could be limited. But that is not guaranteed. Primary concerns
with any TSRA include frequent lightning, low vis/cig, brief
strong wind gusts, and heavy rainfall.

&&

.MARINE...
Issued at 1251 PM CDT Sat May 23 2026

The main marine concerns in the near term will be strong
thunderstorms capable of producing moderate to heavy rain and strong
erratic gusts. Scattered to widespread showers and thunderstorms
will continue to develop and increase in coverage this afternoon and
evening. Waterspouts will also be possible. Scattered activity
continues on Sunday and will persist through much of the week.
Overall, outside of storms, light to moderate onshore winds and low
seas are expected this weekend and into midweek. Pressure gradient
tightens a bit after midweek, resulting in moderate winds and
building seas.

JM


&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  84  69  81  68 /  80  60  30  20
Houston (IAH)  84  72  81  70 /  90  60  60  40
Galveston (GLS)  84  75  83  75 /  80  90  80  50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through Monday evening for TXZ164-177>179-197>200-
     210>214-226-227-235>238-300-313-335>338-436>439.

GM...None.
&&

$$

DISCUSSION...JM
AVIATION...Self
MARINE...JM

NWS HGX Office Area Forecast Discussion