textproduct: Houston/Galveston

KEY MESSAGES

- Shower and storm chances further increase late tonight and Friday as the next storm system moves in. A Flood Watch is in effect for localized heavy rainfall. A few strong to severe cells cannot be ruled out. Hazardous marine conditions are anticipated.

- Rain ends Friday night followed by cooler and breezy conditions for the remainder of the weekend.

- A gradual warm-up during the first half of the week.

DISCUSSION

Issued at 210 PM CDT Thu Apr 30 2026

Stalled frontal boundary near the coast this afternoon and some elevated convection ongoing across northern parts of the area. This will likely continue into the evening. With less cloudiness south of I-10, I wouldn't be surprised to see some late afternoon/evening development right near the front too.

Western upper trough will be advancing toward the area tonight and Friday. With increasing large scale lift, broadening upper diffluence, a series of impulses traversing overhead, deep Gulf moisture in place, a likely developing frontal wave, and sufficient instability/shear...we should see several "waves" of showers and storms track across the region between late tonight and late Friday evening.

All said, we're still looking for a swath of 2-4" rains across parts of the region with some localized 6" amounts possible. Exactly where this swath sets up is dependent on where the surface front and frontal wave develops to our west. There was more uncertainty in previous model runs, but for the most part, 12z guidance is mostly coming on board favoring locations along and north of the I69/I10 corridor for seeing the higher accumulations. A Flood Watch has been issued for a good part of the area...which may or may not need to be adjusted as trends are observed.

**One note about this watch: since the precip will come in multiple waves...I think that the ground should be able to handle most of this rain. As time progresses and the ground becomes more saturated, the primary concern is for locations where this focusing axis sets up...they'll be prone for regenerating/training storms capable of producing significant rain rates that could produce several inches of rain in a short time period. Street flooding will occur in these cases along with some rises on rivers/bayous (see the hydro section below).**

Elevated stronger cells north of the surface front could be a hail risk. Along and south of the surface front (southern/coastal areas) could see an isolated tornado/waterspout and wind risk as well.

This storm system will push east and southeast of the region during the late evening and overnight hours Friday. Colder, drier air will then filter into the region just in time for the weekend.

A gradual modifying/warming trend ensues early next week followed by our next chances of rain toward midweek. 47

AVIATION

(00Z TAF Issuance) Issued at 632 PM CDT Thu Apr 30 2026

Expect poor flying conditions for the next 24 hours with periods of SHRA/isolated TSRA, MVFR/IFR ceilings, reduced visibilities, and gusty winds. The cold front has moved through the Houston terminals this afternoon and was currently over KLBX. Expect the front to reach KGLS this evening. Ceilings will lower to IFR/MVFR levels at remaining terminals this evening in the wake of the front. Scattered SHRA will impact KCLL/KUTS/KCXO this evening. The main precip event will begin after 09Z and last until Friday evening. Mesoscale models show two time windows with enhanced convection: 10-15Z Friday and again 19Z Friday-02Z Saturday. Have TEMPO or PROB30s these periods for TSRA, lower visibilities, and wind gusts 25-35 kts. SHRA should gradually diminish after 02Z Saturday. Winds will back to the north and increase late Friday/Friday evening with gusts 20-25 kts likely inland and 30-35 kts for the coastal terminals.

35

MARINE

Issued at 210 PM CDT Thu Apr 30 2026

Light southeast winds this afternoon will gradually back to a more easterly direction and increase in speed tonight. Caution or advisory flags may be required by late night near the Galveston Bay area with some 15-25 knot speeds or gusts. Winds will further increase on Friday as a storm system moves into the area bringing intermittent strong storms. By late afternoon and early evening a front will be pushing off the coast and north and northeast winds will increase to 25 to 35 knots with some higher gusts and seas will build to 7 to 12 feet Friday night and Saturday. A Gale Warning will likely be required. Rain will taper off Friday night, but winds and seas will remain elevated into Saturday. Conditions should gradually improve Sunday. Light southeast flow returns by Monday. 47

HYDROLOGY

Issued at 210 PM CDT Thu Apr 30 2026

Anticipating multiple waves of heavy rain beginning as early as the pre-dawn hours on early Friday morning. Rainfall rates will likely exceed 2-3" per hour. There is potential for extended periods of heavy rainfall due to training storms, which can cause instances of flooding especially in urban areas, low-lying areas, and areas with poor drainage. The highest rainfall totals are still anticipated to occur along and north of I-10. Currently looking at widespread amounts of 2-4" with isolated higher totals of 6+" possible. This rainfall will cause rises on area rivers and watersheds. Action to minor stage flooding is the most likely outcome, but cannot entirely rule out isolated instances of moderate stage flooding depending on where the most rainfall accumulates. As a result, a Flood Watch has been issued for most of Southeast Texas from 3 AM Friday through 4 AM Saturday

The majority of the area (outside of Harris County) remains in a moderate to severe drought, so most of this will be beneficial rainfall. However, the potential is definitely there for too much rainfall occuring in a short period of time, which can quickly lead to street flooding. Remember that you can monitor updated river forecasts via the NWS NWPS webpage (https://water.noaa.gov/) and as always do not drive through any flooded roadways. Turn Around, Don't Drown.

Batiste/KLG

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 60 61 51 72 / 80 90 60 0 Houston (IAH) 64 67 54 75 / 60 90 80 0 Galveston (GLS) 70 75 59 75 / 40 80 80 0

HGX WATCHES/WARNINGS/ADVISORIES

TX...Flood Watch from 3 AM CDT Friday through late Friday night for TXZ164-176>179-195>200-210>213-226-227-300-313.

GM...Gale Watch from Friday evening through Saturday afternoon for GMZ330-350-370-375.

Gale Watch from Friday afternoon through Saturday afternoon for GMZ335-355.