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ST. PETERSBURG (Miami/AP) — South Florida remains under a Flood Watch through Monday afternoon as Subtropical Storm Alberto continues to drop relentless rain across South Florida and the eastern Gulf Coast.

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Florida, Alabama and Mississippi launched emergency preparations on Saturday.

The National Hurricane Center in Miami issued tropical storm warnings for parts of Florida and Alabama, saying tropical storm conditions are possible there by Sunday night. The governors of Florida, Alabama and Mississippi all declared states of emergency ahead of the storm.

Alberto — the first named storm of the 2018 hurricane season that officially starts June 1 — is expected to strengthen until it reaches the northern Gulf Coast, likely on Monday night.

The NWS said waves as high as 18 feet could pound the popular Gulf beaches in Baldwin County, Alabama, and northwestern Florida on Monday. A high surf warning was in effect through 7 p.m. Tuesday local time.

At 5 p.m. Sunday, center of Subtropical Storm Alberto was located about 165 miles west of Tampa, moving toward the north-northwest near 12 mph.

A Storm Surge Watch is in effect for Crystal River to Navarre, Florida.

A Tropical Storm Warning is in effect from Anclote River to the Mississippi/Alabama border.

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On the forecast track, the center of Alberto will move over the northern Gulf of Mexico Sunday night and approach the northern Gulf Coast in the warning area on Monday.

Heavy rainfall and tropical storm conditions will likely reach the northern Gulf Coast well before the arrival of the center of Alberto.

Alberto is expected to move inland into the Tennessee Valley on Tuesday and Wednesday.

Maximum sustained winds are near 50 mph with higher gusts.

Little change in strength is forecast before Alberto reaches the northern Gulf Coast.

Steady weakening is expected after landfall, and Alberto is forecast to become a tropical depression Monday night or Tuesday.

Winds of 40 mph extend outward up to 115 miles from the center.

A subtropical storm like Alberto has a less defined and cooler center than a tropical storm, and its strongest winds are found farther from its center. Subtropical storms can develop into tropical storms, which in turn can strengthen into hurricanes.

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)