textproduct: Houston/Galveston

KEY MESSAGES

- Flood Watch remains in effect for most of SE Texas.

- Scattered to widespread showers and thunderstorms are expected this afternoon and evening. Some may be strong at times. Locally heavy rainfall is possible leading to the potential of flash flooding. Additional intermittent periods of rain/storms are anticipated Sunday and Monday for parts of the area.

- Mariners should remain weather aware this holiday weekend. Be prepared for higher winds/seas in and near storms and allow yourself plenty of extra time to return to shore before hazardous weather threatens.

DISCUSSION

Issued at 1251 PM CDT Sat May 23 2026

Earlier this morning, a mesoscale convective system moved through, resulting in moderate to heavy rain and strong winds, especially for areas roughly along and south of the I-10 corridor. Rainfall totals of 1 to 2 inches were observed, with some pockets of 2.5 to 3 inches.

Current satellite imagery shows different disturbances over west/central Texas and Louisiana, intensifying as they progress eastward early this afternoon. Locally, radar is picking up thunderstorms developing along an apparent boundary extending along the coast. While the environment stabilized a bit earlier this morning; clearing skies, especially to our west, will allow for destabilization to occur this afternoon as storms to our west reach our area.

So, the next system we're keeping an eye on is the one currently east of the San Antonio area. While hi-res guidance, including the NAM struggled to initialize this complex this morning, most of them are in agreement in bringing this system to southeast TX this afternoon and evening. PWAT values continue to be in the 90th percentile of climatology. That, combined with increasing low to mid level instability, upper-level support and deep surface convergence (boundaries remaining along the coastal counties), will result in scattered to numerous showers and thunderstorms. Current thinking is that this complex of storms will be moving east-northeast into the region this afternoon, mainly focusing along the already mentioned boundary or boundaries that are extending from Jackson to Chambers counties. Latest guidance also indicates a strong 700 mb frontogenesis developing over the region as the main complex moves through. This scenario shows more instability, and hence higher rainfall totals possible. In terms of rainfall totals for this period, an additional 2 to 4 inches can be expected with pockets of higher amounts of 6+ inches possible through tonight. Rainfall rates may peak at 3 to 4 inches/hr. Scattered flash flooding will be possible, especially in areas where have seen repeated storms. In addition to heavy rainfall, isolated to scattered severe thunderstorms will be possible, particularly if this complex becomes into bow segments as they progress east. Damaging winds will be the primary threat; however hail up to quarter size and a brief isolated tornado cannot be ruled out.

Showers and storms should begin to diminish in coverage this evening and overnight. With some boundaries remaining over the region along with some vort maxes aloft, some isolated to scattered activity could potentially continue through the night. Another round of showers and storms can be expected on Sunday; though coverage should be less as we have seen from previous days. Upper forcing will generally remain over our eastern half. That, paired with daytime heating will support activity mainly in the afternoon.

For Monday... convection is again expected as the main upper-lvl low moves across the southern Plains. Not everyone will see rain during the day, but again with diurnal heating and "orphan" surface boundaries meandering over the region; some scattered showers and storms will be possible. The best chances will be for areas east of I-45. While forecast rainfall totals have decreased a bit; a widespread 1 o 2 inches will be possible.

A Flood Watch remains in effect through late Monday.

The rest of the week remains unsettled with periods of showers and thunderstorms continuing through at least Friday. Periods of moderate to heavy rain will be possible, particularly over well saturated soil. Therefore, concerns about isolated to scattered flooding continue to increase. We'll have finer details early in the week as more hi-res guidance comes into agreement. The risk of excessive rainfall is highlighted in the WPC day 4 and 5 outlooks.

JM

AVIATION

(12Z TAF Issuance) Issued at 604 AM CDT Sat May 23 2026

The unstable airmass over our area ended up winning the night, with moderate to heavy SHRA/TSRA occurring this morning at many terminals, especially from IAH to the Gulf. This activity should exit the area over the next couple of hours. However, more disturbances will be moving over our region later today into tonight. Of particular interest is a disturbance over northern Mexico. Heavy TSRA is approaching the Texas-Mexico border this morning as a result. This disturbance is expected to enter our area sometime this afternoon. For now, we have SHRA VCTS prevailing and TSRA TEMPO groups starting around 20-22 UTC. Some uncertainty regarding how much TSRA will occur overnight tonight. If storms the atmosphere stabilizes enough, then overnight TSRA could be limited. But that is not guaranteed. Primary concerns with any TSRA include frequent lightning, low vis/cig, brief strong wind gusts, and heavy rainfall.

MARINE

Issued at 1251 PM CDT Sat May 23 2026

The main marine concerns in the near term will be strong thunderstorms capable of producing moderate to heavy rain and strong erratic gusts. Scattered to widespread showers and thunderstorms will continue to develop and increase in coverage this afternoon and evening. Waterspouts will also be possible. Scattered activity continues on Sunday and will persist through much of the week. Overall, outside of storms, light to moderate onshore winds and low seas are expected this weekend and into midweek. Pressure gradient tightens a bit after midweek, resulting in moderate winds and building seas.

JM

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 84 69 81 68 / 80 60 30 20 Houston (IAH) 84 72 81 70 / 90 60 60 40 Galveston (GLS) 84 75 83 75 / 80 90 80 50

HGX WATCHES/WARNINGS/ADVISORIES

TX...Flood Watch through Monday evening for TXZ164-177>179-197>200- 210>214-226-227-235>238-300-313-335>338-436>439.

GM...None.