A powerful system will be moving through the area later today and through the night and overnight hours before leaving the state early on Wednesday morning. Strong to severe storms will be possible for much of the area, and more likely for the extreme western and southwestern parts of the area, including the threat of tornadoes, damaging winds, and large hail. Here is the latest…Moderate Risk: Locations west of a line from Memphis (Pickens Co.) to Putnam (Marengo Co.).
Enhanced Risk: North and east of moderate risk to a line from Red Bay (Franklin Co.) to Carbon Hill (Walker Co.) to Orrville (Dallas Co.).
Slight Risk: North and east of slight risk to a line from Ardmore (Limestone Co.) to Springville (St. Clair Co.) to Eclectic (Elmore Co.) to Louisville (Barbour Co.).
Marginal Risk: East of the slight risk and includes the rest of the area to the Alabama/Georgia state line.
Threats: Tornadoes (strong tornado possible in Enhanced Risk area), damaging winds up to 70 mph, hail up to and larger than quarter size (1 inch in diameter).
Timing: No change in the timing for the threat of severe storms… Severe threat will start around 2 pm in the western parts of the area and progress eastward throughout the afternoon. The threat will start in the central sections of the area just west of the I-65 corridor around 6 pm, and will continue to progress eastward, with the threat beginning in the east and southeastern parts of the area by roughly 11 pm. All severe threats will be out of the eastern parts of the area by 6 am Wednesday morning.
Flood Watch: From 4 pm today until 7 am Wednesday for Bibb, Blount, Chilton, Dallas, Fayette, Greene, Hale, Jefferson, Lamar, Marengo, Marion, Perry, Pickens, Shelby, St. Clair, Sumter, Tuscaloosa, Walker, and Winston counties in Central Alabama, and Colbert, Cullman, Franklin, Lauderdale, Lawrence, Limestone, Madison, and Morgan counties in North Alabama.
Flash flooding caused by excessive rainfall is possible. Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Flooding may occur in poor drainage and urban areas. Forecast rainfall totals are in the 1-3 inch range in the watch area.
Wind Advisory: From 10 am today until 7 am Wednesday for all counties in North and Central Alabama. South winds 15 to 25 mph with gusts up to 40 mph expected. Gusty winds could blow around unsecured objects. Tree limbs could be blown down and a few power outages may result. Use extra caution when driving, especially if operating a high profile vehicle. Secure outdoor objects.
There will be the potential of rogue supercells that may develop out well ahead of the main squall line that will begin the severe threat as early as 2 pm for the western and southwestern parts of the area. These will move north-northeastward through the afternoon, and these will bring the greatest risk of tornadoes to those locations in the moderate and enhanced risk locations. Conditions are conducive enough that a strong, long-track tornado of EF2 strength or greater will be possible in those locations. Most of those cells will eventually mix in with the main squall line later in the early evening over the northern parts of the area. As the line moves across the central to eastern parts of the area, severe risks will be on the decline as conditions will become less unstable even though damaging winds and a couple of brief spin-up tornadoes will remain possible.
Models continue to show lower instability values out ahead of the main squall line, with the instability briefly picking up just out ahead of it. However, it does not take that much instability to get severe weather in North/Central Alabama during the Spring severe weather season. It looks like that for much of the area outside of the moderate and enhanced risk areas, the main threat will be damaging winds and hail, with a low risk of a few brief spin-up tornadoes.
Also, heavy rain can be expected with a few locations potentially having some flooding issues especially over the west and northwestern parts of the area as rainfall amounts could reach or exceed 3-4 inches through 7 am Wednesday morning. If you are out and about and come across a water-covered road, turn around and don’t drown. It is better to avoid risking your life and others in such perilous circumstances when patience should prevail.
And finally, winds have already become gusty and could reach as high as 30-40 mph outside of any thunderstorm activity. Use caution while driving, especially in a high profile vehicle. Also, be sure all outdoor furniture and fixtures are secured. Tree limbs and smaller trees may fall resulting in damage to structure and loss of power.
Have multiple and reliable ways to get severe warnings and never just rely on an outdoor siren. Your best option is a NOAA Weather Radio. Have your emergency alerts activated on your phones and have a trusty weather app installed (such as Baron Threat Net and your favorite local news app). Have your safe place and plan of action ready, and have helmets and hard-soled shoes for each person. If you live in a mobile or manufactured home, know where you are going to seek shelter (community shelter, local business, family or friends, etc.), and have your mode of transportation ready to go.
As long as you have a way to hear warnings and have a safety plan, you will be fine. While the odds of any one location being struck by a tornado is very low, it is better to be ready and act immediately when a warning is issued.
As soon as a tornado watch is issued this afternoon, I will focus all of my attention on the Alabama Weather Blog. You can find my posts at AlabamaWx.com and on the Alabama Wx Weather Blog Facebook page (@alabamawxblog).