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.
As temperatures rise through the weekend in the South, so will the risk for heat-related dangers.
While heavy rainfall inundated the Phoenix area with historic flooding, deadly landslides occurred in Japan, claiming dozens of lives.
While a tropical low is expected to brew into Tropical Storm Cristobal this weekend, the East Coast of the U.S. is being monitored for future impacts -- even if the storm remains well offshore.
United States residents may pay higher heating costs this fall as colder air is expected to grip the Rockies and Plains at times and some quick-hitting chilly shots may impact the Northeast.
A swath of soaking rain will slowly shift from the northern Plains to the Canadian Prairies this weekend, making people reach for their umbrellas and heightening concerns for flooding.
While residents will face more disruptions to outdoor activities on Saturday, dry air will push southward across Pittsburgh to end the weekend.
San Lorenzo, Puerto Rico (1906)
103 degrees, hottest ever in Puerto Rico.
East-Central Kentucky (1980)
2-1/2 to 3 inches of rain in 45 minutes. 75 homes were flooded and one was washed off its foundation, ending up blocking a roadway in the community of Beauty (near the WV-KY line). Heavy damage was reported, there including a washed-out bridge.
Wichita Falls, TX (1980)
108 degrees -- new record high for this date, also the 56th day of the last 59 days that they have reached 100 degrees or more.