Tropical Storm Chantal, moving westward toward Mexico's Yucatan Peninsula and Belize, was headed for a landfall on Monday night or early Tuesday, according to the National Hurricane Center here.
"We expect landfall tonight or early tomorrow morning," said meteorologist Eric Blake.
As for the location, "It's hard to pinpoint," Blake said. It may be the southern part of the Yucatan Peninsula or northern part of Belize."
"There's a slight possibility of it becoming a hurricane, but we don't think that will happen before it makes landfall," Blake said.
The tropical storm maintained its top winds of 65 mph, still shy of the 74 mph threshold to become a hurricane, forecasters said.
A hurricane watch was issued for the Yucatan's Caribbean coast from Belize City to the Mexican resort center of Cancun, alerting residents to expect hurricane-force winds within 36 hours.
At 5 a.m. EDT, the ragged center of the storm was about 245 miles east-southeast of Chetumal, Mexico. Tropical storm winds extended outward as far as 200 miles.
Chantal was moving west-northwestward at 15 mph (24 kph) and was expected to stick to that course, dumping 3 to 5 inches of rain along its path. The hurricane center expected little change in the storm's speed or the strength of the wind over the next 24 hours.
Chantal rolled over the Lesser Antilles earlier this week, causing no significant damage, then lost strength but it fortified again over Friday. Lightning linked to Chantal killed two people in Trinidad on Thursday.