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National Weather Service Forecast Discussion

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407
FXUS64 KHGX 222346
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
646 PM CDT Fri May 22 2026

...New AVIATION...

.KEY MESSAGES...

- The Flood Watch has been expanded to now include Polk, Trinity,
  San Jacinto, Walker, Grimes, and Washington counties and is now
  in effect through late Monday.

- 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 306 PM CDT Fri May 22 2026

As we head into the late afternoon hours, focus turns towards
potential for thunderstorm development, especially during peak
daytime heating. Current thinking is for the convective
temperature to be reached somewhere in the 4 to 7 pm time frame.
The severe weather risk is low, but any strong storms could be
capable of producing gusts up to 40 mph.

The forecast for this Memorial Day weekend remains on track.
Southwesterly flow aloft will continue to bring multiple vorticity
maxes/disturbances across the region tonight into at least early
next week. At lower levels, persistent south-souteast flow continues
to filter in a warmer and very moist airmass further inland. In
fact, PWAT values are near or above the 90th percentile of
climatology for this time of year. With that being said, the
environment continues to be favorable for periods of showers and
thunderstorms, some locally moderate to heavy. Confidence is high
that periods of showers and thunderstorms will move through the
region from Saturday through early next week. However, confidence in
specific details regarding the timing and location of the heaviest
rain amounts is still moderate, given the nature of these types of
mesoscale features.

Speaking of confidence, some hi-res guidance brings an MCSs close to
our region overnight through Saturday morning. Confidence in its
occurrence is low to moderate; however, the environment continues to
remain favorable for any convection. The passage of this MCS could
either lower PoPs on Saturday or enhance the activity during the day
when combined with daytime heating and any outflow boundary (- ies).
The next best round of showers and storms returns on Sunday with
another MCS moving in from our south. Additional rainfall amounts of
2 to 4 inches can be expected through late Monday. Isolated higher
amounts of 5 to 6 inches will be possible. Rainfall rates are
expected to peak in the 3 to 4 inches per hour range in the heaviest
downpours.

The Flood Watch has now been expanded to include counties north of I-
10 and is now in effect until late Monday night. WPC highlights this
threat in their Day 2 and 3 excessive rainfall outlook with a slight
risk (level 2 of 4). In terms of severe weather, some of these
storms could become strong to marginally severe on Saturday if the
environment remains unstable in the afternoon. Damaging winds will
be the main risk.

Forecast rainfall amounts have trended lower for Monday. While the
upper level pattern remains active with continued southwesterly flow
aloft, most models are suggesting some drier air will filter in from
our west. Will continue with some diurnally driven isolated to
scattered activity mainly for the afternoon and evening. The next
period to monitor will be Tuesday into Wednesday as another strong
disturbance moves through potentially bringing more rounds of
moderate to heavy rain. We will provide more details on this system
earlier in the week.

JM

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 623 PM CDT Fri May 22 2026

VFR conditions currently across the SE Texas area along with S-SE
winds at 4-12 KTS. A mix of VFR-MVFR cigs are expected overnight
into early Sat morning and some sites could have vis reductions
due to the development of patchy fog. Fog, if any, is expected to
burn off around 15Z. Winds will be less than 5 KTS for most
locations overnight, then 5-10 KTS after 14Z.

A few rounds of showers and thunderstorms are expected for much
of the day Sat as a mid-upper level disturbance moves into Texas.
Model guidance has not been performing will with the timing and
placement of shower and thunderstorm activity these past few days,
and we still see a few differences in the latest model runs for
tomorrow`s activity. Thus, I have placed PROB30s and TEMPOs for
this TAF set, but we might be dealing with several AMDs as the
event unfolds. Some strong storms will be capable of producing
strong VRB wind gusts. Llvl wind shear may also occur along with
llvl turbulence. SPC has placed a Marginal Risk (level 1 of 5) of
severe thunderstorms, mainly for strong winds and hail.

There might be a few hours during the late evening/early night
period where activity decreases a bit, however, we might still be
affected by additional showers and thunderstorms rolling in during
the overnight period.

Cotto

&&

.MARINE...
Issued at 306 PM CDT Fri May 22 2026

Light onshore winds and low seas will continue this weekend and
persist through the upcoming week. Scattered to numerous showers and
thunderstorms is expected over the next several days. Locally heavy
rain will be possible. The main concern will be strong winds and
elevated seas with any strong storms.

JM

&&

.HYDROLOGY...
Issued at 306 PM CDT Fri May 22 2026

Multiple rounds of moderate to heavy rainfall are expected this
evening through Monday. The first round will start tonight bringing
2-4 " with isolated higher amounts of 5-6+". 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. The
greatest concern for the heaviest rainfall is Saturday afternoon
through Sunday morning, but there is the possibly of heavy
downpours through the entire weekend.

Rises to action to minor flood stage are likely though the weekend
especially on flashier responding basins. Isolated moderate to major
stage flooding is not out of the question depending on where the
most rainfall accumulates. We will need to monitor area rivers and
bayous over the next several days to see exactly where the heaviest
rain falls. Remember that you can monitor updated river forecasts
via the NWS NWPS webpage (https://water.noaa.gov/).

Going into next week, we will have monitor the forecast for
additional moderate to heavy rainfall on top of primed soils as this
will generate more runoff than normal. That being said, it is still
too early to tell exactly which basins will have long term issues.

Landry-Guyton

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)  70  82  68  80 /  40  80  60  60
Houston (IAH)  74  84  71  81 /  20  80  80  70
Galveston (GLS)  76  85  75  83 /  20  60  90  80

&&

.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...Cotto
MARINE...JM
HYDROLOGY...Landry-Guyton

NWS HGX Office Area Forecast Discussion