textproduct: Houston/Galveston

KEY MESSAGES

- Light showers/virga expected throughout the day on Monday, especially along and west of I-45.

- Chances for thunderstorms return Tuesday into Wednesday with the potential for another round of locally heavy rainfall.

- Gradual warming trend throughout the work week with shower/storm chances increasing again going into the weekend.

DISCUSSION

Issued at 1040 PM CDT Sun Apr 19 2026

With drier air filtering in throughout the day, some of us got to enjoy peaks of sunshine and others did not. Areas around Matagorda Bay were probably like "y'all got to see the sun?!" as PW values remained near or above the 75th percentile (~1.36") leading to persistent cloud cover. Even though there's a bit of drier air at the surface, there is enough saturation in the mid to upper levels paired with an embedded shortwave leading to light rain/sprinkles. Some of the rain is likely evaporating before reaching the surface (virga), but obs down there have been reporting a trace to 0.01" of rain here and there so some droplets are definitely reaching the surface. Keep this in mind when we talk about Monday's forecast! While the northeasterly winds will be lighter tonight, cloud cover will be on the rise overnight as moisture increases due to surface high pressure kicking out to the east rather quickly. Typically, the coldest night behind a cold front is the second night following FROPA. This is one of those rare occasions where the first night (Saturday night) was the coldest.

Monday may feature slightly cooler daytime high temperatures though due to a mixture of the 850mb high remaining nearby (cooler temperatures aloft), mostly cloudy skies, and scattered light rainfall. High temperatures are expected to range from the upper 60s to low 70s. As moisture continues to increase from southwest to northeast, an embedded shortwave will push through and pair with a strengthening LLJ overhead going into late Monday leading to scattered light rain showers. This light rain could be a bit widespread especially in the afternoon hours. Current model trends shows this mainly being a west of I-45 issue in the morning, then spreading eastward in the afternoon as lift becomes more favorable with the LLJ strengthening along with moisture expansion. Now if you look at model radar reflectivity, then look at a model sounding you'll note that there's quite a bit of dry air at the surface. Recall from the previous paragraph that we had a similar environment on Sunday and received some light rain/sprinkles at the surface...but the dry air layer is anticipated to be a bit deeper on Monday (if you believe the HRRR it's around ~3km). Light rain/sprinkles can't entirely be ruled out for Monday, especially along and west of I-45. There certainly will be some evaporation above the surface, but some raindrops will survive the trek to the ground. Certainly not a rainout, but something to note! The more convective rainfall returns on Tuesday/Wednesday.

The increase in moisture is mostly due to the development of a coastal trough/low that develops on Monday along the South TX coast. This pairs with yet another embedded shortwave trough and some added instability. With PW values near or exceeding the 90th percentile (~1.58"), there is some potential for locally heavy rainfall. As a result, WPC has outlined most of Southeast TX in a marginal risk (level 1 of 4) of excessive rainfall on Tuesday and Wednesday. Keep in mind that this is taking into account the somewhat more saturated soils from Saturday's heavy rainfall, which would lead to quicker transitions to runoff. Current QPF totals show a general widespread 1-2", but locally higher amounts will be possible. With PW values near the 90th percentile, we can anticipate rainfall rates to be in the 2-3+"/hr range again.

While there is slight downward trend in moisture availability on Thursday, there will be enough in place to pair with more embedded shortwaves for some isolated to scattered afternoon convection. What I haven't mentioned up till now is that ridging aloft will be in place throughout most of the work week. Outside of the rain chances, there will be a general warming trend throughout the week (after Tuesday) with high temperatures returning back into the mid to upper 80s towards the end of the work week. Our attention then turns to an upper level low moving through the CONUS towards the end of the work week and an approaching frontal boundary, which brings our next chance of showers/storms going into next weekend.

Batiste

AVIATION

(00Z TAF Issuance) Issued at 623 PM CDT Sun Apr 19 2026

Predominately VFR overcast conditions across our terminals this evening, with some MVFR ceilings possible to the southwest around LBX. Light and variable winds overnight will gradually increase through the morning to 8-12 kts out of the east. LBX will have the best shot at seeing shower activity Monday as the highest rain chances reside well west of the I-45 corridor.

McNeel

MARINE

Issued at 1040 PM CDT Sun Apr 19 2026

Small Craft Advisories remain in effect for the Gulf waters through late Sunday night, but small craft will need to exercise caution through at least Monday night. Winds and seas are expected to take a while to subside below the caution flag threshold. Wind speeds remain elevated, but will gradually transition to easterly overnight and southeasterly by Monday night. An extended fetch of moderate southeasterly winds around midweek will likely lead to another round of increased seas, especially in the offshore Gulf waters. This may lead to another period of caution flags on Wednesday into Thursday for the Gulf waters. Scattered light rain is expected on Monday, but chances for storms return Tuesday into Wednesday as an upper level disturbance pushes through. Water levels are expected to remain near 3.0 feet above Mean Lower Low Water during high tide cycles through at least midweek.

Batiste

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 55 69 58 68 / 10 30 70 80 Houston (IAH) 57 70 61 71 / 10 30 50 80 Galveston (GLS) 68 74 69 77 / 10 40 50 70

HGX WATCHES/WARNINGS/ADVISORIES

TX...None. GM...Small Craft Should Exercise Caution through late Monday night for GMZ330-335-350-355-370-375.

Small Craft Advisory until 1 AM CDT Monday for GMZ350-355-370- 375.