textproduct: Houston/Galveston

KEY MESSAGES

- Multiple rounds of thunderstorms are expected this week with the first round arriving tonight. Strong to severe storms will be possible with damaging winds as the main threat. Locally heavy rainfall also expected.

- Rain and storm chances remain elevated through the entire holiday weekend with periods of locally moderate to heavy rain, potentially leading to localized flooding.

- The threat of hazardous rip currents remains through at least midweek before marine hazards transition to thunderstorm-driven waves.

DISCUSSION

Issued at 305 PM CDT Tue May 19 2026

Wetter conditions are expected this week and into Memorial Day weekend with multiple rounds of moderate to heavy rain.

Synoptically speaking, a broad longwave trough will continue to deepen and move across the Rockies and into the Plains today, persisting through the rest of the week. With a persistent southwesterly flow aloft, this trough is helping to eject multiple impulses of energy/disturbances ahead of it, resulting in increased dynamics/forcing across the region. At the surface, a warm and very moist airmass (PWAT near/at the climatological max for mid-May) along with an approaching frontal boundary from the north, will be enough to support a daily risk of showers and storms.

This afternoon/early evening: A warm and humid airmass remains in place over the region. With moderate instability, and weak boundary (-ies) meandering over the area; we expect to see isolated to scattered activity.

Tonight into Wednesday: The first round of scattered to widespread showers and storms is expected as early as this evening, continuing into early Wednesday. Early this afternoon, satellite and surface obs showed a cold front slowly moving southeast into north-central TX. While this front is forecast to remain to our west, a fairly unstable warm and moist airmass ahead of it, combined with deep moisture convergence due to a developing surface trough, and forcing aloft could potentially lead to scattered to widespread showers and thunderstorms. We will continue to monitor these clusters of storms as they could potentially evolve into a line of bowing segments, capable of producing damaging winds. SPC highlights this threat in their Day 1 Outlook with a slight risk (level 2 of 5) of severe weather across our far western counties, and a marginal risk (level 1 of 5) elsewhere. In addition to strong to severe storms, locally moderate to heavy rain is expected with the strongest storms. Forecast rainfall amounts of 1 to 3 inches can be expected with isolated higher amounts of 5 to 7 inches possible. Rainfall rates of 2 to 4 inches per hour will likely leading to localized flash flooding along with quick responses on area rivers and creeks. Rain/storms should gradually taper off early Wednesday morning. While a lull in activity is possible during the day, cannot ruled out isolated to scattered showers/storms popping up in the afternoon with the peak of daytime heating.

Thursday and Friday: Periods of showers and storms will continue as more disturbances aloft move through the region. The next mesoscale convective system is forecast to move through on Thursday during the day, with an additional isolated to scattered activity on Friday. Specific details on the exact timing and location of the heaviest rain remain difficult to determine; however, widespread rainfall totals of 1 to 2 inches will be possible with isolated higher amounts up to 4 inches possible.

Memorial Day Weekend ( Saturday - Monday): A continuos parade of disturbances aloft combined with sufficient deep moisture will support additional periods of showers and storms through the entire holiday weekend. Based on the latest trends, forecast rainfall totals of 4 to 6 inches are possible. Locally higher totals possible,especially with the strongest storms. With the ground already saturated from previous rainfall, soils will be primed for runoff, leading to flooding problems in areas of heavy downpours. While confidence is high for a wet weekend, confidence in the exact timing and location of the heaviest rain is low. Initial rounds of storms early in the week will potentially affect any storms later in the week. Focus on the potential impacts and stay tuned to the latest forecast, especially if you have outdoor plans this Memorial Day weekend.

See Hydrology section below for more information on forecast rainfall and potential flooding.

JM

AVIATION

(12Z TAF Issuance) Issued at 627 AM CDT Tue May 19 2026

SHRA and isolated TSRA over the area will dissipate over the next few hours. MVFR cigs expected to trend VFR by the afternoon, with SE winds becoming more ESE later in the day. We still anticipate a line of SHRA/TSRA to move into the area from the north and west this evening / overnight. However, confidence in the forecast (especially regarding TSRA timing and severity) is quite low. In addition, the wind direction/speed forecast is uncertain tonight into Wednesday morning. The primary concern from TSRA will be strong gusty winds.

MARINE

Issued at 305 PM CDT Tue May 19 2026

Winds and seas will continue to weaken/subside this afternoon, with only some building seas up to 8ft persisting well offshore through early this evening. Multiple rounds of showers and thunderstorms are expected this week, with the first one starting tonight and extending into early Wednesday morning. A few of these storms will be capable of becoming strong to severe with strong winds as the main threat. Locally heavy rain will also be expected. A daily risk of showers and storms will continue this week and persist through the Memorial Day weekend. Light to occasionally onshore winds should prevail through the period; however, stronger gusts are possible in the vicinity of thunderstorms. Regarding beach conditions, there is a high risk of rip currents persisting through the weekend.

JM

HYDROLOGY

Issued at 305 PM CDT Tue May 19 2026

Multiple rounds of moderate to heavy rainfall are expected this evening through Monday. The first round will start tonight bringing 1-3" with isolated higher amounts of 5-7+". 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. 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 Saturday 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/).

Landry-Guyton

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 69 83 70 80 / 70 50 40 100 Houston (IAH) 71 86 73 84 / 70 60 30 100 Galveston (GLS) 75 85 78 85 / 70 60 10 70

HGX WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk through Wednesday evening for TXZ436>439.

GM...Small Craft Advisory until 7 PM CDT this evening for GMZ370-375.