textproduct: Houston/Galveston

KEY MESSAGES

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

- Isolated showers/storms possible overnight, isolated to scattered showers/storms on Monday, followed by increasing chances of showers and storms for the rest of the week.

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

DISCUSSION

Issued at 1212 AM CDT Mon May 18 2026

I'm gonna go ahead and lead in with the main takeaways for this discussion: have an umbrella/poncho with you throughout the week, remain weather aware by staying up to date on the latest forecasts, and have multiple ways to receive alerts of impactful weather. That's your big three for this week.

A band of showers is setting up over Central Texas and is gradually pushing into Southeast Texas this evening. PW values remain well above the 90th percentile (~1.79") and when you pair that with a strengthening LLJ (30-40 kt) and embedded shortwaves, you get *vaguely gestures at radar reflectivity* that. Some of the latest 00Z CAM guidance indicates the potential for isolated embedded thunderstorms overnight as well. Based on the instability and lifting mechanism in place (the LLJ), this is an entirely plausible outcome (and not only because it's already occuring). This is most likely to occur near or north of I-10 during the overnight hours, so don't be surprised if you wake up before your alarm to some rumbles of thunder...Happy Monday! Monday will feature isolated to scattered showers with a non-zero chance of an isolated storm or two in the afternoon mainly north of I-10. Outside of the rain chances, it's gonna be warm and muggy. High temperatures will continue to top out in the upper 80s to low 90s with heat index values peaking in the upper 90s/low 100s. A rinse and repeat for Tuesday, but definitely more so on the rinse part of that as we head into late Tuesday.

The wet pattern that we're moving into Tuesday and beyond is courtesy of a longwave trough that is becoming established over the western CONUS. Southwesterly flow aloft will lead to embedded shortwaves passing through the area with the first notable one being on late Tuesday. Exact timing is still uncertain (as always when trying to time shortwaves), but we're currently looking at Tuesday evening for the first round of showers/storms. This shortwave is expected to result in a line of showers/storms, or if you want to be fancy you can call it a Mesoscale Convective System (MCS) that pushes into the area on Tuesday evening. A few of these storms could be strong to severe and be capable of producing strong wind gusts and hail. As a result, majority of Southeast Texas is outlined in a marginal risk (level 1 of 5) of severe weather on Tuesday. The severe weather outlook may change with the overnight update, so be sure to stay tuned to the forecast. The line of storms is visible at the very end of 00Z CAMs and we can see convection beginning to approach the Brazos Valley right around 7pm Tuesday evening.

Additional rounds of showers and thunderstorms are anticipated throughout the week with the most likely mechanism being more MCS's especially along a nearby frontal boundary that makes its closest approach around midweek. Where this boundary lingers/stalls will be key to who gets the most amount of rainfall this week. With PW values remaining near or above the 90th percentile, locally heavy rainfall will be possible. There is additional details down below in the Hydrology section. A brief summary of it is, the rounds of rain earlier in the week will help to prime the soils. This means that rounds of rain later in the week could result in a quicker transition to runoff which increases the potential for minor/street flooding. We've already seen in recent events over the past few weeks that PW values in this range can result in 3-4+"/hr rainfall rates in the heaviest downpours.

As a result, all of Southeast Texas is outlined in a marginal risk (level 1 of 4) Tuesday through at least Thursday. I say at least because with rain chances sticking around into the weekend, there is decent potential that at least portions of the area will remain outlined in the Excessive Rainfall Outlook. Speaking of Thursday, a portion of the Brazos Valley is outlined in a slight risk (level 2 of 4) of excessive rainfall on Thursday. Training convection along the lingering frontal boundary cannot be ruled out. Be sure to stay tuned to the forecast for the latest details.

As far as rainfall totals go, we continue to anticipate widespread totals of 2-4" with isolated amounts of 4-6+". This is for the Tuesday through Friday timeframe, and those higher end amounts are still most likely to occur north of I-10. The frontal boundary continues to linger going into the weekend alongside a steady dose of passing shortwaves and elevated PW values, so chances for showers/storms continue going into the weekend. With daily chances for moderate to heavy rainfall, we'll be keeping an eye on area rivers/streams...that's another hint to check out the Hydrology section below.

In case you wanted to know more about the temperature forecast, there's a downward trend going into midweek with the increasing rain chances (surprise surprise). We go from high temperatures in the upper 80s/low 90s on Monday and Tuesday to the low to mid 80s midweek and beyond. The temperature forecast will likely change based on timing and location of these rounds of showers/storms. I( can mention though that we'll at least flirt with record high minimum temperatures early this week with low temperatures only bottoming out in the upper 70s/low 80s. Yeah...some of y'all might not drop below 80 overnight. Now that's what I call humid!

Batiste

AVIATION

(00Z TAF Issuance) Issued at 618 PM CDT Sun May 17 2026

For the 18/00 TAF update, the atmospheric pattern remains on a similar track with MVFR cigs (BKN020s) predominant in the southeast Texas airspace through most of all periods. As of the start of the period, MVFR cigs have already crept as far north as KCXO with KCLL and KUTS not far behind. MVFR cigs will continue through 18/15Z before starting to slowly lift (near-shore terminals will most likely keep MVFR cigs through the full period). By 19/02Z, another round of MVFR cigs is expected to reach KIAH, while robust southerly surface winds continue across the airspace at 10-15 kts, gusting to 20-25 kts.

Cassel

MARINE

Issued at 1212 AM CDT Mon May 18 2026

Small Craft Advisories remain in effect through Tuesday morning as moderate onshore winds and elevated seas continue to persist. Winds and seas gradually subside on Tuesday. Multiple rounds of showers and thunderstorms are anticipated beginning late Tuesday through at least the end of the work week. Some of these storms could produce strong wind gusts, especially if they push offshore in the form of a line of storms. Outside of the storms, onshore winds will persist generally in the 10-15 kt range after Tuesday.

The other topic of interest for mariners is the continued high risk of rip currents and potential for minor coastal flooding during times of high tide. Water levels at Galveston Bay Entrance reached 3.3 ft MLLW during high tide on Sunday morning. P-ETSS guidance continues to indicate water levels being slightly higher than that during high tide Monday morning peaking closer to 3.5 ft MLLW. Water levels during high tide on Tuesday morning are currently expected to peak just above 3.0 ft MLLW. A Beach Hazards Statement remains in effect through Monday morning and will transition to a Rip Current Statement afterwards through Tuesday evening (for now). Expect the rip current risk to remain high through at least midweek.

Batiste

HYDROLOGY

Issued at 1212 AM CDT Mon May 18 2026

Anticipating multiple rounds of moderate to heavy rainfall Tuesday through at least Friday. 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 near or above the 90th percentile (~1.79"), 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 minor/street flooding. We continue to anticipate widespread rainfall totals of 2-4" with isolated higher amounts (4-6+" possible). 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 isolated instances of moderate 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/).

Batiste

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 90 78 89 72 / 10 20 60 70 Houston (IAH) 89 79 89 75 / 20 10 40 70 Galveston (GLS) 86 81 86 79 / 20 10 20 60

HGX WATCHES/WARNINGS/ADVISORIES

TX...Beach Hazards Statement until 10 AM CDT this morning for TXZ436>439.

High Rip Current Risk from 10 AM CDT this morning through Tuesday evening for TXZ436>439.

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