Severe Weather Episode Likely on Monday

Aiming To Prepare, Not To Scare

Severe Weather Episode Likely on Monday

The potential exists for all modes of severe weather across a large portion of Alabama Wednesday afternoon and evening. There could be very large hail, destructive winds, and a few tornadoes some of which could be strong.

The afternoon outlook update from the Storm Prediction Center puts much of Alabama under a Slight Risk, but far northern Alabama under Enhanced Risk. The Enhanced Risk area is where we could see more significant severe weather events, such as large hail, damaging winds and a few strong tornadoes.

…SUMMARY…
Tornadoes, damaging winds and hail are expected across parts of
Middle Tennessee, much of northern Alabama, far northeast
Mississippi and northwest Georgia. A strong tornado or two is
possible during the late afternoon. Severe wind gusts are also
possible into northern Florida.

…Tennessee Valley/Central Gulf Coast States/Western and Central
Georgia…
An upper-level low will move across the Ozarks on Monday as a 70 to
80 kt mid-level jet translates eastward through the base of the
system. At the surface, a low will gradually deepen as it moves
eastward into the Tennessee Valley. A warm front extending
east-southeastward from the low will advance east-northeastward
across the Tennessee Valley during the day. Scattered elevated
thunderstorms will likely be ongoing during the morning on the cool
side of the front in northeast Arkansas and further to the southeast
in parts of Alabama and Georgia. As the surface low moves into
middle Tennessee during the mid to late afternoon, surface-based
convective initiation is expected to occur from near the low
southward along the Mississippi-Alabama state-line to the west of
Tuscaloosa. This convection will likely develop southward across
north-central Alabama and move eastward into western Georgia by
early evening. Convective coverage should gradually expand and MCS
development will be possible Monday evening.

Concerning the severe potential, a corridor of moderate instability
is forecast to develop by afternoon from eastern Mississippi into
much of Alabama. NAM forecast soundings at 21Z in eastern
Mississippi and near Birmingham show MLCAPE values reaching the 2000
to 2500 J/kg range. In addition, the mid-level jet will create
strong deep-layer shear profiles across most of the region. Forecast
soundings across the slight risk area by late afternoon show 0-6 km
shear generally in the 60 to 65 kt range. This environment will
support severe thunderstorm development from the mid afternoon
through much of the evening. The shear should be favorable for
supercell formation especially from middle Tennessee southward into
north-central Alabama where hailstones of greater than 2 inches in
diameter, wind damage and a tornado threat will be possible. A
strong tornado may occur with any supercell that can become
dominant. The potential for very large hail is also forecast
southeastward into parts of western Georgia where vigorous
convective development may take place during the early evening. The
wind damage threat may increase by early evening especially if a
mesoscale convective system can organize.

TIMING: The severe weather threat begins Monday afternoon and lasts through the late night hours.

IMPACTS: All modes of severe weather are likely, with the greatest threat being damaging winds up to 70 MPH and tornadoes. A strong tornado or two cannot be ruled out. There is also a threat for large hail. A minimal flash flooding threat will exist depending on how the supercells train over each other.

NWS GRAPHICS: 


MODEL DATA:

CAPE values begin to ramp up across Alabama from southwest to northeast beginning around 1:00 PM. With this kind of atmospheric setup storms will have the potential to be supercellular in nature.

http://climate.cod.edu/data/forecast/animations/12Z-20180318_NAMSE_con_sbcape-30-48-50-100.gif

This is the nail-biting model data run to look at. As we look at helicity/shear values, they nearly max out around 3:00pm. If storms tap into this kind of energy there could be the potential for stronger tornadoes.

http://climate.cod.edu/data/forecast/animations/12Z-20180318_NAMSE_con_3kmhel-30-48-50-100.gif

Now that we know what energy there is, we look at where the storms will potentially fire up. That’s what reflectivity run is for:

http://climate.cod.edu/data/forecast/animations/12Z-20180318_NAMSE_prec_radar-30-48-50-100.gif

Doesn’t look like much, but when you think of it any storm that fires up will tap into a great amount of energy.

Now is the time to prepare for this event. Have a severe weather plan, know where to go and what to have.

We will keep you updated here at Alabama Weather Prediction. The best way to receive our updates is by going to awpwx.org/live where we provide live updates for events like this. Additionally you can tune into our new Messenger platform for periodic updates.

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