Your need to knows about today’s severe weather, flash flooding threat

Tuesday was a First Alert Weather Day due to the potential of strong and severe storms as well as a flash flooding threat.

A very strong low-pressure system, which brought devastating storms through Texas on Monday, progressed east today and will bring a threat for severe weather to the Tennessee Valley this afternoon. The Storm Prediction Center has highlighted much of the southeast in its outlook for severe weather this afternoon. In fact, a Moderate Risk (Level 4 of 5) outlines much of southern Mississippi & Louisiana.

Here in the Valley, we are placed in a Marginal & Slight risk for storms, which are levels 1 and 2 respectively. Don’t let that “lessened” category fool you, we still have the potential for severe storms this afternoon, we just have a few variables that are in question.

Let’s break it down here:

STORM IMPACTS

Storms will bring the potential for damaging straight-line winds of 60+ mph, isolated, embedded tornadoes, as well as heavy rain and flooding. Large hail is possible as well, but it is the lowest threat of the four. The greatest threat for damaging winds and tornadoes will be for the area of Northwest Alabama to the west of I-65.

Heavy rain will become the major threat into the late evening and overnight. Because of this, a Flood Watch has been issued for Colbert, Cullman, Franklin, Lauderdale, Lawrence, Limestone, Madison, & Morgan counties in North Alabama and will be in effect from 4 PM Tuesday until 7 AM Wednesday. Franklin, Giles, Lawrence, Lincoln, & Moore counties are in Middle Tennessee are included in the Watch as well. Locally heavy rainfall of 2 to 3 inches will be possible for many areas of Northwest Alabama, with localized heavier amounts possible as well.

Not only will storms be an issue, but winds before the storms even move in will be an issue. A Wind Advisory is in effect today from 10 AM until 7AM Wednesday as winds from the south will ramp up through the day and gusts of 25 to 45 mph will be possible. These winds could lead to some tree damage as well as isolated power outages. Loose, unsecured items/objects could be tossed around as well.

TIMELINE:

Storms will move in ahead of a cold front in a long line of storms. These will move in as early as 3 PM in Northwest Alabama and the severe threat should end in Northeast Alabama around 9 PM. At this point, you can expect the storms into the Huntsville/Madison metro somewhere around 5 PM to 6 PM.

Storms will last through the overnight and into early Wednesday. There will still likely be a few showers lingering for Wednesday morning’s commute. From there we will see more clouds roll in from the west-northwest. Temperatures on Wednesday will be into the upper 50s and low 60s. Winds will be from the west at 15 to 30 mph. From there we will stay cool and dry through the remainder of the week. Highs will stay into the low upper 50s and low 60 with sunshine!

WHAT WE NEED TO WATCH:

When forecasting storms we look for many ingredients, but there are four main factors that really determine severe weather. I use the acronym of S.L.I.M. This covers Shear, Lift, Instability, & Moisture. Shear is a measure of the spin in the atmosphere, which you need for storms to turn and strengthen. Lift is what helps these storms develop with an upward motion to push the storms higher in the atmosphere. Instability measures the energy in the atmosphere for storms to feed off of. The higher those levels, the stronger storms are able to become. Lastly, moisture. You can’t have storms without moisture, but the higher the levels, the better the threat for strong storms.

As you see above, the parameters do not look as high as you would like to see for severe weather. That is why our risk is a little lower than our neighbors to the southwest. However, that doesn’t mean that these variables can’t/won’t change as we move through the day today. If we see an influx of higher moisture then our instability will also increase which would amplify our threat for storms this afternoon. Either way, the threat is there and needs to be monitored.

As always, make sure to stay weather alert this afternoon. You can stream our coverage this afternoon on your 48 First Alert Weather App as well as on our streaming apps on Roku, Amazon Fire, and Apple TV devices. Keep checking in for the latest forecast as we get into the thick of things!

Meteorologist Brandon Spinner

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