textproduct: Houston/Galveston

KEY MESSAGES

- Warm, breezy, and muggy conditions will continue for the next several days.

- Multiple rounds of showers/storms expected beginning late Tuesday through the end of the work week. A few storms could be strong to severe and multiple rounds of rainfall could lead to minor/street flooding.

- Elevated winds, seas, and rip current risk in the bay/Gulf waters and beaches through at least midweek.

DISCUSSION

Issued at 344 PM CDT Mon May 18 2026

BLUF: The weather pattern begins to change this week with multiple chances for rain and storms continuing well into the Memorial Day weekend. Localized heavy rain and isolated to scattered strong to severe thunderstorms will also be possible. Remain weather aware this week for the latest forecast updates and make sure you have multiple ways to receive alerts.

A warm and muggy start to the workweek with mostly cloudy skies and breezy southerly winds. A few showers and storms will be possible in the afternoon despite a strong 700:850 mb capping inversion. Strong moisture transport along with a decent LLJ will be enough to support this activity this afternoon and evening. A warm and muggy night is anticipated with lows in the upper 70s to near 80s.

A deep longwave trough deepening over the Rockies will continue to eject multiple impulses of energy along the southwest flow aloft. This parade of disturbances will move through Southeast Texas while at the surface, a frontal boundary will attempt to sag southward into north-central TX before stalling somewhere between the Dallas/Fort Worth area and the Brazos Valley region through the end of the week. Total rainfall amounts will strongly depend on where this boundary stalls. The first round of showers and thunderstorms (first round of a series of mesoscale convective systems (MCS's)) is forecast to arrive to Southeast TX on Tuesday. Given the nature of these shortwaves, it is difficult to pin-point specific timing. Latest hi-res guidance suggests scattered activity in the afternoon, bringing the first MCS Tuesday evening into Wednesday. Forecast rainfall amounts during this time frame is expected to be between 1 to 3 inches with isolated higher amounts possible.

Scattered showers and storms will continue on Wednesday before the next MCS's arrives early Thursday and additional systems persists into the weekend. With PWAT values near/at the climatological max for this time of year, combined with enough forcing and a deep warm cloud layer, rounds of moderate heavy rainfall will be possible. As noted in the previous discussion, earlier rainfall this week will serve to prime the soil. This saturated grounds will lead to a rapid transition to runoff, especially in areas experiencing repeated rounds of rain. Under this type of scenario, rainfall rates of 3 to 4+ in/hr are possible in the heaviest downpours. Overall, 3 to 6 inches of rain is forecast Thursday through Sunday, with localized higher amounts possible.

Hazards:

Severe Weather: Thunderstorms could become strong to severe with the first round of storms Tuesday into Wednesday. There is a Slight risk of severe weather mainly for our northwestern counties (Brazos Valley). The main severe weather risk is damaging winds. Hail up to a quarter sized will also be possible.

Heavy Rainfall:

A Marginal risk of excessive rainfall (level 1 of 4) is expected most of the week. A slight risk (level 2 of 4) is forecast for Thursday for portions of the Brazos Valley area.

We will continue to monitor trends as these systems evolve in the coming days. A Flood Watch may need to be considered later this week. Stay tuned to the forecast not only through the week but also through the holiday weekend as this unsettled pattern looks to remain through early next week.

JM

AVIATION

(12Z TAF Issuance) Issued at 543 AM CDT Mon May 18 2026

Widespread MVFR cigs should generally trend VFR this morning. Coastal areas may struggle break out of MVFR cigs, but perhaps a brief period of VFR could occur this afternoon like yesterday. Winds will continue to be gusty and out of the southeast. Sustained winds are expected to average in the 15-20 knot range, with gusts over 25 knots expected in some areas. Cigs should trend back to MVFR by evening and overnight.

MARINE

Issued at 344 PM CDT Mon May 18 2026

Moderate to strong onshore winds and building seas (5 to 8 ft) will continue through Tuesday morning. A Small Craft Advisory remains in effect through mid Tuesday morning. Winds and seas will gradually weaken/subside by Tuesday afternoon, though gusts between 15 to 10 knots will continue through the week. Several disturbances will move across the bays and Gulf waters throughout the week, resulting in scattered showers and thunderstorms, some of which may be locally moderate to heavy. Some storms could become strong Tuesday night into Wednesday with gusts of 30 to 40 mph.

A high rip current risk continues along all Gulf-facing beaches. Given the persistent onshore flow, this risk will likely continue through the end of the week.

JM

HYDROLOGY

Issued at 344 PM CDT Mon May 18 2026

Anticipating multiple rounds of moderate to heavy rainfall Tuesday through at least Saturday. These rounds are expected to mostly be in the form of Mesoscale Convective Systems (MCS's). The exact timing of these storms can be a bit tricky as mesoscale factors play a key role (hence the name), but we anticipate the first round to come late Tuesday. With PW values exceeding the 90th percentile (~1.7-2.1"), rainfall rates will likely exceed 3-4"/hr in the heaviest downpours. While these lines of storms are typically progressive, the rainfall received early in the week is expected to prime the soils for rounds later in the week. Saturated soils leads to a quicker transition to runoff which brings an increased risk of flooding. We continue to anticipate widespread rainfall totals of 5-7" with isolated higher amounts. The highest rainfall totals are still expected to occur north of I-10.

This rainfall will generate runoff and cause rises on area rivers and watersheds. Action to minor stage flooding is the most likely outcome, but cannot entirely rule out moderate to isolated major stage flooding 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) 77 88 73 83 / 20 30 70 90 Houston (IAH) 78 88 76 86 / 20 20 60 80 Galveston (GLS) 79 86 79 86 / 10 20 50 30

HGX WATCHES/WARNINGS/ADVISORIES

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

GM...Small Craft Advisory until 9 AM CDT Tuesday for GMZ330-335-350- 355-370-375.