The National Weather Service expects the heaviest rain from a multi-day storm system to hit coastal counties Saturday and Sunday, raising the flood risk for communities that include Friendswood, Webster, Seabrook, Nassau Bay and Clear Lake Shores.
The NWS Houston/Galveston office said on X Thursday, Oct. 1, that the rain threat will shift from northern and western counties to coastal counties over the weekend, warning of possible street flooding and minor watershed rises.
The agency's most likely forecast calls for 2 to 3 or more inches of rain along the coast Saturday through Sunday. Galveston is projected at 2.77 inches. A reasonable high-end scenario pushes totals to 3 to 4 or more inches, with Galveston at 4.62 inches.
That marks a sharp change from the Thursday-through-Friday outlook, which showed just 0.28 inches for Galveston while the Brazos Valley bore the brunt of the storm.
What's driving the rain
A weak cold front interacting with deep Gulf moisture is expected to move slowly across the area this weekend, according to the NWS forecast page. The heaviest rainfall totals are expected over the coastal counties. CW39 Houston reported Thursday, Oct. 1, that the front could stall near the coast, with 2 to 4 inches possible south of I-10 from Saturday through early next week.
Through Friday, the NWS warned that rainfall rates of 2 to 4 inches per hour are possible in the heaviest storms. General totals for coastal counties Saturday through Sunday range from 1 to 3 inches, with isolated pockets of 3 to 5 inches.
The moisture traces back to the remnants of Pacific Hurricane Polo, which made landfall in Mexico before tracking east across Texas.
Flood risk levels
The NWS Excessive Rainfall Outlook for Thursday night placed a Moderate Risk (Level 3 of 4) near College Station, with a Slight Risk (Level 2 of 4) extending southeast. By Friday into Saturday, the risk maps shift to Level 1 Marginal and Level 2 Slight across Houston and coastal areas.
No Flood Watch had been issued for the Clear Lake area as of Thursday afternoon. No statements from Friendswood, Webster, Seabrook, Nassau Bay or Clear Lake Shores emergency management offices addressing the weekend forecast were found in public records as of publication.
KPRC 2 reported Wednesday, Sept. 30, that the weekend street-flooding threat is rated medium, with repeated rounds of rain posing the greatest concern.
A cold front early next week is expected to end the rain and bring cooler air, according to CW39. The NWS advises residents to have multiple ways to receive weather warnings. Updated forecasts and any watch or warning upgrades will be posted at weather.gov/hgx.
