textproduct: Houston/Galveston

KEY MESSAGES

- Scattered afternoon showers and storms may bring locally heavy rainfall Today.

- Gradual warming trend with temperatures reaching the upper 80s by the end of the work week.

- Lower rain chances Thursday through the weekend. Cannot rule out some stronger or severe storms on these days either.

DISCUSSION

Issued at 1158 PM CDT Tue Apr 21 2026

A midlevel ridge is expected to pass over SE Texas today, putting our areas in a northeasterly flow pattern aloft. Subsidence from the ridge should result in a noticeable decrease in overall rainfall coverage for today. However, embedded impulses passing through the ridge, along with daytime heating, should still be sufficient to bring showers to the area. They'll initially start as light, sporadic showers this morning, increasing in coverage as the day progresses. Daytime heating should slowly kick in, producing some scattered thunderstorms during the afternoon. With deep moisture over the region, the strongest storms could end up producing heavy downpours, which may result in some locally heavy rainfall. Generally rainfall totals are forecasted to be around an inch or less, though models show that those isolated higher-end totals could reach upwards of 3-5 inches. WPC has portions of SE Texas under a Marginal (level 1/4) Risk of heavy rainfall for Today, though this is a fairly common scenario for our area, where one or two spots may see a heavy amount of rainfall while others see relatively little by comparison. Any of those stronger downpours could result in some ponding on roadways and minor street flooding, especially in urban areas. Either way, showers and storms should taper off into the evening with quieter weather overnight.

Thursday will see rising mid level heights and generally less shortwave impulses passing overhead in this semi-zonal flow pattern. While there should be some better instability and shear, showers and storms should largely be isolated in nature. Otherwise, conditions should be warm with highs in the mid/lower 80 and lows in the upper 60s/lower 70s.

Friday through the weekend will be a rather interesting period of the forecast to watch. SE Texas will remain in a predominantly zonal flow pattern throughout this period of the forecast as temperatures rise. Long range ensembles show ample shear and instability in place across portions of the Southern Plains/Lower Mississippi River Valley during this period. Over SE Texas specifically, SFC CAPE is forecasted to range from around 1700-2800 J/KG with 500mb shear around 30-45 knots. Several troughs/disturbances are forecasted to pass to the north of our area around this time, though as a result, much of the best lift and forcing will keep north of our area as well. This explains why models are producing low PoPs through the weekend. Still, if any storms can get started, this environment does appear conducive for severe weather. SPC currently has a Slight (level 2/5) Risk of severe weather up against our northern boarder on Friday, Saturday, and Sunday as well. While it's not directly in our CWA for all of these days, we're still several days out, and any southerly shift in the shortwaves/impulses could result in this risk shifting into our area. Given the WNW flow aloft as well, it'll be worth monitoring as we draw closer to the end of the week.

On Monday, a much more robust shortwave trough is anticipated to fill north across the Plains, sending a cold front towards SE Texas. Decent shear and instability remain present, though models suggest the front may slow/stall around the Brazos Valley/Piney Woods area. A subtropical mid-level high then builds in from the south on Tuesday, allowing low rain chances and warmer weather to continue.

03

AVIATION

(00Z TAF Issuance) Issued at 613 PM CDT Tue Apr 21 2026

Showers should taper off this evening with only sparse rain chances overnight. MVFR to IFR CIGs are anticipated to scatter out in may areas for a brief period in the evening, then fill back in early Wednesday morning. Scattered showers start to develop across the region again early on Wednesday with coverage slowly rising into the late morning as CIGs scatter/lift in most spots. Scattered thunderstorms may develop over portions of SE Texas Wednesday afternoon. Showers and storms should taper off during the late afternoon, with only light and very sparse showers anticipated Wednesday night.

03

MARINE

Issued at 1158 PM CDT Tue Apr 21 2026

Elevated winds of around 15 to 20 knots are anticipated across the nearshore coastal waters from High Island to Freeport early this morning. Small craft should exercise caution to allow winds to subside. Light to moderate southeasterly winds should continue through the later half of the work week. A long fetch of these southeasterly winds may bring increased seas at times. This with, periodically higher winds may warrant caution flags at times. Scattered showers and thunderstorms will be possible today with rain chances decreasing into Thursday. Above normal water levels near 3.0 feet MLLW are still expect at each high tide cycle through the end of the work week.

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PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 61 77 66 83 / 30 50 20 0 Houston (IAH) 63 80 68 84 / 40 70 20 10 Galveston (GLS) 70 79 73 80 / 40 60 20 10

HGX WATCHES/WARNINGS/ADVISORIES

TX...High Rip Current Risk until 1 AM CDT Wednesday for TXZ436>439.

GM...Small Craft Should Exercise Caution until 1 AM CDT Wednesday for GMZ335.

Small Craft Should Exercise Caution until 7 AM CDT Wednesday for GMZ355.