UPDATE: New data Wednesday evening shows some adjustments in the arrival times of heavy rain Thursday afternoon.
Widespread heavy rain will bring a risk for flash flooding to the entire Tennessee Valley Thursday afternoon through Friday morning. Potentially 2-5 inches of rain could fall in 12-18 hours, which could lead to flash flooding and rising rivers, creeks, and streams.
A Flash Flood Watch is in effect from 6 PM Thursday until 9 AM Friday for Madison, Morgan, Limestone, Marshall, Lauderdale, Colbert, Franklin, Lawrence, Jackson, and DeKalb counties in Alabama and for Lincoln County in Tennessee. This includes all of the Tennessee Valley within the WAAY 31 coverage area.
A Wind Advisory is in effect from midnight Wednesday night until midnight Thursday night/Friday morning for the entire Tennessee Valley.
Occasional light showers are possible from 4 AM through about 1 PM Thursday. The heaviest rain will begin between 1 PM and 3 PM across Northwest Alabama, including Florence, Muscle Shoals, Tuscumbia, Waterloo, Leighton, Cherokee, Russellville, and Moulton. The heavy rain will track eastward into Huntsville, Madison, Athens, Decatur, Hartselle, Laceys Spring, and Fayetteville starting between 3 PM and 5 PM. The heavy rain will increase starting between 5 PM and 7 PM around Scottsboro, Hollywood, Bridgeport, Guntersville, Boaz, Fort Payne, Collinsville, Section, and Geralidine.
The rain will fall through Thursday night and Friday morning. The heaviest rain will begin slackening after 10 PM, then mostly light rain will linger after midnight. Some occasional heavy rain will be possible, especially over Sand Mountain. Rain will diminish after 6 AM Friday and fade to an end by midnight.
Severe thunderstorms are not likely. Wind gusts up to 35-40 mph are possible. That wind can happen away from thunderstorms. Over a saturated ground, wind that strong can uproot trees. Rainfall amounts of 1-3 inches will be widespread. Locally higher amounts up to 5 inches are possible. Be ready for slippery roads, localized street flooding, and poor visibility. You should plan post-Christmas holiday travel accordingly.
Rivers are expected to rise with this heavy rain and more rain this weekend. the Paint Rock River near Woodville is forecast to rise above flood stage Friday and Saturday. Other rivers are expected to stay just below flood levels, but some can rise high enough to saturate their banks and become dangerous. These include the Flint River at Brownsville, the Tennessee River at Florence, the Tennessee River near Guntersville, and the Tennessee River near Scottsboro.