Already responsible for triggering significant flooding across Puerto Rico, Isaac threatens to cause similar problems across Hispaniola, Cuba and Jamaica into this weekend.
After moving through the Leeward Islands earlier this week and south of Puerto Rico on Thursday, Isaac was moving south of Hispaniola Friday with showers and squalls spreading into the island and across Puerto Rico.
The worst effects in terms of rain in these areas will occur through Saturday morning as tropical moisture is pumped in on the eastern flank of the storm.
Puerto Rico was being inundated by torrential rain and an outer spiral band from Isaac Friday. Some roads have been blocked by mudslides or flooded. At least one bridge was washed out along the southern part of the island.
San Juan, P.R. radar from 1:15 p.m. EDT, Friday, Aug. 24, 2012.
"Training-effect rain and thunderstorms were blasting Puerto Rico like a giant fire hose during Friday," Expert Senior Meteorologist Alex Sosnowski said.
Isaac will be in a favorable environment for strengthening with warm water and weak wind shear.
Isaac may strengthen into a Category 1 hurricane before it reaches Cuba on Saturday. However, as Isaac interacts with the higher terrain of Cuba on Saturday, it should weaken once again.
"We are likely to see more bands of intense, persistent rainfall set up on Hispaniola, Cuba and even for a time yet in Puerto Rico into the weekend," Sosnowski added.
AccuWeather Senior Meteorologist Dan Pydynowski expects 4-8 inches of rain to fall across Puerto Rico, Hispaniola and Cuba with the potential for 10 inches or more in the mountains.
Coastal flooding occurred near Duffs Bottom on the western end of Tortula, British Virgin Islands Thurs., Aug. 23, 2012. Image taken by Radi Hassan.
A westward shift in Isaac's track on Friday will likely spell more trouble for Jamaica than previously thought.
A total of 1 to 2 inches of rain will overspread the island into Saturday. Locally higher totals are a concern and could lead to flash flooding and mudslides, especially across eastern areas.
Additionally, tropical storm-force winds will lash the southern half of the Dominican Republic, Haiti and eastern Cuba through Saturday. Hurricane-force winds are also a threat along southwestern Haiti and eastern Cuba.
AccuWeather.com Meteorologist Steve Travis contributed to this article.
Warmth is forecast to build over much of the eastern half of the nation by July, with Alaska of all places helping out.
The storms could affect cities from St. Louis to Evansville, Ind., Louisville, Ky., Cincinnati and Dayton, Ohio to Huntington, W.Va.
A tornado touched down at Denver International Airport as a severe weather system moved through the area.
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A slow-moving tropical depression will continue to bring torrential rainfall and the risk of flooding to parts of southeastern Mexico, Belize and Guatemala into midweek.
Some of the warmest weather of the year will continue across Alaska over the next few days, challenging more records.
Elizabeth City, NC (1991)
2.83" of rain in 2.5 hours.
East Coast (1893)
Hurricane arrived off Cape Cod, after crossing Florida and sweeping the Southeast coast.
Wellesly Hills, MA (1998)
2.35" of rain in 35 minutes.