McALLEN, Texas — Texas mobilized National Guard troops and residents along the Gulf Coast near the Mexican border were buying plywood, flashlights and other supplies as Tropical Storm Dolly — expected by forecasters to strengthen into a hurricane this week — headed their way.

Hurricane warnings were issued late Monday for parts of the Texas and Mexico coasts, meaning hurricane conditions were expected in those areas by the end of today.

Dolly was expected to make landfall later this week and bring with it high winds and 10 to 20 inches of rain in coastal areas. Emergency officials feared major flooding problems and urged coastal residents to prepare.

Gov. Rick Perry activated 1,200 National Guard troops and other emergency crews and Shell Oil said it was evacuating workers from oil rigs in the western Gulf of Mexico.

Even as far up the coast as the Houston area, Harris County officials told residents to be ready in case the storm changes course and heads their way.

The National Hurricane Center in Miami issued a hurricane warning from Brownsville north to Port O'Connor. Meanwhile, a tropical storm warning was issued from Port O'Connor to the San Luis Pass, a strait south of Galveston.

Mexico also announced a hurricane warning from Rio San Fernando north to the U.S. border. A tropical storm warning and a hurricane watch were also in effect from La Pesca to Rio San Fernando.

Forecasters said Dolly was expected to make landfall late today or early Wednesday as a Category 1 hurricane, which has with sustained winds of 74 mph to 95 mph.

Texas officials said they wouldn't order evacuations along the coast unless Dolly strengthens to a Category 3, with sustained winds of at least 111 mph.

At 5 a.m. EDT today, the center of Tropical Storm Dolly was located about 295 miles southeast of Brownsville. It was moving west at about 15 mph and had maximum sustained winds near 60 mph. Tropical storm-force winds extended outward up to 160 miles. Dolly's winds were expected to strengthen today to hurricane force, which would mean at least 74 mph.

There are about 2 million people in the Rio Grande Valley, which includes popular summer beach resort South Padre Island. Officials readied to evacuate residents in flood-prone areas and urged RV owners on South Padre to head for higher ground.