The National Hurricane Center’s rainfall forecast for Hurricane Isaias reads 4 to 8 inches across southern Alabama, the Florida Panhandle and Big Bend, and southwest Georgia, with localized totals up to 15 inches. That is the language of Public Advisory 10, issued at 10 p.m. CDT Thursday, Oct. 8, and it comes with a flat statement that flash and river flooding are likely once the storm moves ashore Friday night.
The coastline will take the wind and surge. Inland counties, many of them on wetter-than-normal soils according to the Weather Prediction Center, face the slower hazard of water that has nowhere to go.
The 15-inch ceiling in NHC Advisory 10
The advisory’s rainfall section separates the broad forecast from the worst case. Most of the named area is expected to collect 4 to 8 inches from Friday through the weekend, and the 15-inch figure is the localized maximum, meaning a few spots under persistent bands rather than the region as a whole. The same section adds that an isolated tornado risk begins Friday night in coastal Alabama, the Florida Panhandle and far southwest Georgia. The coastal Carolinas get a separate, lower line in the same product: 3 to 5 inches.
Isaias is forecast to turn north on Friday and accelerate, which limits how long any one place sits under the heaviest rain. The 10 p.m. discussion puts the center over central Alabama by early Saturday and weakening quickly, so the totals depend on whether bands set up and repeat over the same ground before the storm passes through.
Weather Prediction Center flash flood risk: Moderate for southern Alabama and southwest Georgia
The Weather Prediction Center, which handles national rainfall forecasting, takes a more conservative view of the totals. Its extended discussion, issued at 4:23 p.m. EDT Thursday, calls for 3 to 7 inches with localized amounts up to 10 inches, much of it falling in a 12-to-18-hour window, and it notes that the storm’s speed keeps the heaviest rain in any single area relatively short.
The risk category is nonetheless high. A Moderate Risk of excessive rainfall covers southern Alabama and the western Florida Panhandle, and it extends on Friday into far southwestern Georgia, where neighborhood probabilities of more than 5 inches exceed 70 percent across much of that zone. The discussion expects numerous flash floods, some of them significant, with urban areas such as Mobile and Pensacola most exposed, and it flags low-lying ground around concave bays where surge can block drainage.
For Saturday, the WPC outlines a higher-end Slight Risk across much of Georgia. Training storms along a persistent inflow band could produce flash flooding from the Panhandle and Big Bend northward, and the discussion says upgrades are possible if confidence in that band’s position grows. The agency’s Excessive Rainfall Outlook page showed a Day 1 Slight Risk covering about 9.2 million people and 23,769 square miles for the period beginning 8 p.m. CDT Thursday.
Flood watches from the Tallahassee and Birmingham forecast offices
Local offices are working with their own numbers, and they do not match. The National Weather Service in Tallahassee, whose area includes southwest Georgia, lists a Flood Watch from Friday afternoon into Saturday evening with widespread 5 to 10 inches and locally higher totals of 10 to 15 inches, plus a Moderate Risk of excessive rainfall over the Panhandle, southeastern Alabama, the Big Bend and parts of southwest Georgia.
Farther north, the National Weather Service in Birmingham has a Flood Watch for all of Central Alabama from 7 p.m. Friday through 7 a.m. Sunday, with 2 to 4 inches and locally up to 5. That page, last updated at 10:14 p.m. CDT Thursday, also lists a Tropical Storm Warning for southern Central Alabama and a High Wind Watch for northern portions late Friday night into Saturday. The spread, from 2 to 4 inches in Birmingham’s area to 10 to 15 in Tallahassee’s, follows the forecast track: the offices closest to landfall carry the biggest numbers.
Rivers, soil and the Friday-night timing
The NHC statement that river flooding is likely, alongside flash flooding, means the water problem is not confined to the hours of the heaviest band. The agency’s Advisory 10 text puts the rain over Friday and the weekend, and its discussion has Isaias a post-tropical remnant over Alabama by Saturday evening, still inland on Sunday evening and dissipated by Monday evening.
The tornado threat arrives on a similar clock. NWS Tallahassee rates the tornado risk in southwest Georgia as a Slight Risk, Level 2 of 5, highest there on Friday and widening across the region on Saturday, while Birmingham expects isolated tornadoes as the storm moves north across Central Alabama.
What none of the products settle is which towns actually land under the 15-inch spots. The NHC calls them localized, and the WPC’s lower ceiling of 10 inches suggests the wetter outcome depends on a rain band stalling in a place no model has yet pinned down.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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