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.
Travel hazards, delays and disruptions associated with rain, ice and snow will continue over the Central states through the balance of the Thanksgiving weekend.
The current reprieve from heavy rain across southern India will not last long with the threat for flooding downpours set to return for the final days of November.
Sandra is weakening and no longer a major hurricane but remains on track to make landfall in western Mexico with flooding rainfall on Saturday.
Heavy thunderstorms will continue to shift northward across central South America with the greatest threat for flooding focusing on northeastern Argentina and eastern Paraguay into Saturday morning.
Several days of heavy rain will bring the potential for significant flooding from the southern Plains to the middle Mississippi Valley into early next week.
Nation devastated by terrible floods -- 400 people killed.
O'Fallon, MD (1990)
Strong downburst from a thunderstorm caused an apartment to collapse, injuring 25 people.
New England Coast (1898)
Famous "Portland" storm formed off Cape Cod with loss of 200 lives. Many others were lost to the raging sea in 50 small vessels. A total of 27 inches of snow in New London, CT; 15 inches at Waterbury, CT. Peak wind was 72 mph in Boston. Boston received more than a foot of snow.