textproduct: Houston/Galveston

KEY MESSAGES

- Isolated to widely scattered showers and thunderstorms possible through at least Wednesday along with hot and humid conditions.

- Less humid and a tad less hot later in the week.

- Possible wetter pattern next week.

DISCUSSION

Issued at 1100 PM CDT Mon Sep 21 2026

There is good deterministic and ensemble guidance support for an increasingly amplified mid/upper flow pattern as the week progresses. Texans should find ourselves under a building ridge while a deep layer trough digs southward over E CONUS and another trough over the U.S. Pacific Coast. We'll continue with the daily risk of isolated to widely scattered diurnally forced showers and thunderstorms through at least Wednesday. Couldn't rule out a locally heavier thunderstorm. Beyond Wednesday, increased ridging coupled with a push of dry air from the north and northeast should lower PoPs and humidity. Temperatures through Wednesday are expected to be in the mid/upper 90s (around 90 at the beaches) with triple digit heat index values. By week's end, we are expecting highs in the low/mid 90s with heat indices below 100 degrees. Overnight temperatures likely to become somewhat cooler by the end of the week as well.

There may be a pattern change by early next week, featuring an increase in moisture from both the Gulf and tropical East Pacific. In addition, there's decent ensemble support for a breakdown in ridging early next week. Both ECMWF / GFS ensemble means show 500MB heights falling from near 595 dam late this week, to around 585 dam by early/mid next week. There is not a strong signal for "fall-like" temperatures. That being said, there is an increasing signal for above average rainfall. The current 8-14 day precipitation outlook from the Climate Prediction Center is leaning towards a wetter pattern next week. The Madden Julian Oscillation (MJO)is expected to amplify into Phase 1 later this week and into next week. MJO composites for this time of year show a strong correlation between phase 1 and a wetter pattern across SE Texas. Temperature wise, phase 1 correlates with slightly warmer than normal temperatures.

If we do see more clouds and rain, then I suspect afternoon highs next week could easily drop into the 80s. But if the pattern mimics what we're seeing in the ensemble data, then it'll likely be muggy. Guidance continues to show cold fronts that try to make it down to SE Texas in early October (also a potential rain maker). We shall see if any of them can push far enough to the south to bring "real" fall weather down to SE Texas.

Self

AVIATION

(06Z TAF Amendment) Issued at 1100 PM CDT Mon Sep 21 2026

VFR will persist through the overnight hours. Patchy fog is possible at KCLL and KCXO around sunrise as well as along the coast, with periods of FEW/SCT MVFR CIGs possible. There is again a chance of showers and thunderstorms in generally the same areas as today (highest to the northeast and along the coast). However, confidence is not high enough at this time to include PROB30s at any specific site. Light winds will continue, although brief gusty and erratic winds are possible within any thunderstorms.

AP

MARINE

Issued at 1100 PM CDT Mon Sep 21 2026

Isolated to scattered showers and thunderstorms are possible over the next few days. The best chance of a thunderstorm over the Gulf will be during the overnight and morning hours. In the bays, the highest risk will be late morning and early afternoon. Winds should average 10-15 knots from the east to northeast this week, with occasional periods in the 15-20 knot range. Gulf seas are expected to average 2-3 feet, though could increase slightly later in the week.

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 75 98 76 98 / 30 20 10 0 Houston (IAH) 78 97 79 96 / 0 20 10 0 Galveston (GLS) 82 92 83 91 / 30 20 20 10

HGX WATCHES/WARNINGS/ADVISORIES

TX...None. GM...None.