textproduct: Houston/Galveston

KEY MESSAGES

- Isolated showers and thunderstorms today, generally along the coast east of Galveston.

- Higher chances of storms for northern areas Monday.

- Hot temperatures with daily isolated to scattered diurnal thunderstorms for much of the upcoming week.

DISCUSSION

Issued at 1227 PM CDT Sun Sep 20 2026

An upper ridge continues to encompass the forecast area, however latest water vapor imagery indicates mid and lower level moisture approaching the area from the west along an associated trough. This will bring a return of the humidity albeit not to the same extent as such that prompted the Heat Advisories last week. Heat indices are expected to be around 103-105F today, so continue to use caution if outdoors for extended periods. The afternoon sea breeze will help initiate some onshore thunderstorms, although they still look to be confined along the coast and generally east of Galveston. Per usual, these will taper off around sunset. The aforementioned trough will track eastward overnight. Although the timing is unfavorable, the wave/vort max is potent enough that a few weak storms will be possible in our northern counties overnight where the greatest associated forcing will be present. As such, some mentionable 10% PoPs have been added for this time period. With the moist air returning along with the usual daytime instability, PoPs have also been increased in this same area for the afternoon hours, before ending in the evening.

The forecast remains on track for the rest of the week. The overall pattern will bring hot and humid conditions during the day with isolated-to-scattered sea breeze initiated diurnal thunderstorms. These look to become less prevalent towards the end of the week as an upper ridge builds over the area and subsequently brings stronger capping. Temperatures will slightly cool by the end of the week as well, but still remain a few degrees above average for this time of year, generally in the low-to-mid 90s.

AVIATION

(00Z TAF Issuance) Issued at 657 PM CDT Sun Sep 20 2026

The isolated convection that developed earlier this afternoon has mostly dissipated as we approach sunset. VFR conditions continue to prevail alongside southeasterly winds around 6-12 kt with occasional gusts near 15-20 kt. Winds will become light and variable later this evening through Monday morning. We continue to monitor the progression of a boundary and associated convection moving through central TX currently. High-resolution model guidance is still in agreement on convection dissipating before it makes it into southeast TX. As we saw earlier this morning, the potential for intermittent periods of patchy fog at CXO/UTS continues. Winds will remain southeasterly on Monday but should remain more in the 5-10 kt range.

Added in PROB30s for isolated to widely scattered thunderstorm development in the afternoon hours. Currently have these relegated to the northern and coastal terminals, but can't entirely rule out additional PROB30 groups being needed for the Houston metro terminals depending on how the models trend.

Batiste

MARINE

Issued at 1227 PM CDT Sun Sep 20 2026

Southeast winds peaking around 10 kts are expected today and Monday. These will back to northeasterly Tuesday and veer due easterly Wednesday/Thursday sustained at 15-20 kts, before slightly diminishing thereafter. Seas of 1 to 4 ft will persist, highest on Thursday afternoon. Isolated-to-scattered coastal and offshore thunderstorms are expected each day, slightly tapering off towards the end of the week.

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 76 97 75 97 / 10 30 20 10 Houston (IAH) 78 95 78 97 / 0 10 0 10 Galveston (GLS) 83 90 82 91 / 10 20 0 20

HGX WATCHES/WARNINGS/ADVISORIES

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