April 29: Tonight's Thunderstorm Forecast

The thunderstorm forecast for tonight is very low as a weather disturbance comes through the Upper Midwest. The maximum chances for storms will exist mainly on the US/Canada border in North Dakota. The best chances will be up to 70%, so I would expect some spotty storms.
Storms will be exiting Florida at midnight, which is when this image is valid. Offshore, there will be quite a squall line. It will probably produce ample waterspouts, so ships in that area should watch out.
Everywhere else should be clear of storms.

April 27 Aftermath: 4/29 Preliminary Results of Tornadoes (Birmingham, AL NWS Office)

Location(s)	Damage Survey Status
Hackleburg	EF-3+ Tornado. Winds: At least 180mph. Path Length: 25.2 miles, Path Width 3/4 mile. Further Evaluation Underway.
Other portions of Marion, Lamar, Fayette, and Winston Counties	Shotsville: EF-3+ Tornado. Winds: Around 140mph. Path Length: 19.1 miles in Marion County . Path Width: 3/4 mile. Further Evaluation Underway. Haleyville: EF-3+ Tornado. Winds: Around 140mph.Path Length: 31.8 miles, Path Width: 3/4 mile. The track may have continued into the Tennessee Valley.
Pickens County into Northern Tuscaloosa County	Ongoing (Aerial)
Walker and Blount Counties	Ongoing (Aerial)
Tuscaloosa	Ongoing (will likely take several days)
Jefferson County/Birmingham Metro	Ongoing (will likely take several days)
Western portions of Tuscaloosa-Birmingham Supercell (Sumter and Green Counties)	Ongoing Today
Eastern portions of Tuscaloosa-Birmingham Supercell (Saint Clair to Cherokee County)	Ongoing Today
Sumter-Green-Hale-Bibb-Shelby Counties	Being Finalized
Pell City-Talladega-Calhoun-Cleburne Counties	Saturday 4/30
Marengo (continuation from Choctaw County)	Being Finalized
Perry-Dallas-Chilton Counties	Saturday 4/30
Autauga-Elmore-Tallapoosa-Chambers (including Dadeville)	Ongoing Today

April 27 Aftermath: How did the Tornado Outbreak occur?

Such an outbreak like the April 27 one is extremely rare and historic when it happens.
The big question is, how did this happen?

1. JET STREAM

The jet stream was down south, guiding the low pressure center east with the cold front that would produce the tornadoes. The jet stream was unusually strong, and the storm system may have even gotten some of that energy from the jet stream.
The jet stream made for a high wind shear event, favorable for tornadoes in some areas.
Additionally, the jet stream separates warm and cold air. With the cold front bringing the cold air from above the jet stream and the warm front bringing warm air from below the jet stream, it was a very volatile situation to start with.

2. EHI
EHI (Energy Helicity Index) combines wind factors (like helicity, which is a spinning motion) and energy factors (like CAPEs, which produce stronger and more volatile storms) to make a sense of what the potential is for rotating supercells.
The EHI index was incredibly high for the outbreak.
Values may have reached 12.00, which is considered absolutely unbelievable.
This is probably the biggest factor that directly contributed to the tornado outbreak.

3. CAPE
CAPE values indicate potential energy that can be utilized by thunderstorms. The higher the CAPE, the more unstable the atmosphere. CAPE values were witnessed to be up to 4,000 j/kg, possibly even more.
To give you a sense of how unstable 4,000 j/kg is, 2,000 j/kg is considered the threshold for severe thunderstorms for CAPE values.

There were many other things that came into place, but these 3 really stood out from the other factors.
Stay tuned to the Weather Centre for continuing coverage on the aftermath of this horrific incident.

Death Toll from Historic April 27 Tornado Outbreak Spikes

The death toll from last night's tornado outbreak has unfortunately spiked.
At least 173 people are confirmed dead.
Mississippi: 32
Alabama: 128
Dekalb County in Alabama was the hardest hit, with 30 people dead there alone.
There are also fatalities in Arkansas, Georgia, Tennessee.

A witness to the tornado that hit Birmingham indicated it was at least a mile wide.
The mayor of Tuscaloosa described Tuscaloosa's infrastructure as 'decimated'.
80,000 chickens escaped as well.

The Weather Centre holds people affected in our thoughts and prayers today.

April 27: Tornado Warning- Bristol, TN

THE NATIONAL WEATHER SERVICE IN MORRISTOWN HAS ISSUED A

* TORNADO WARNING FOR...
EXTREME EASTERN HAWKINS COUNTY IN EAST TENNESSEE...
SULLIVAN COUNTY IN EAST TENNESSEE...
EXTREME NORTHERN WASHINGTON COUNTY IN EAST TENNESSEE...
RUSSELL COUNTY IN SOUTHWEST VIRGINIA...
SCOTT COUNTY IN SOUTHWEST VIRGINIA...
WASHINGTON COUNTY IN SOUTHWEST VIRGINIA...
CITY OF BRISTOL IN SOUTHWEST VIRGINIA...

* UNTIL 1000 PM EDT

* AT 915 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR COLONIAL
HEIGHTS...OR NEAR KINGSPORT. DOPPLER RADAR SHOWED THIS TORNADO
MOVING NORTHEAST AT 70 MPH.

* LOCATIONS IN THE WARNING INCLUDE...
BRISTOL TN...BRISTOL VA...ABINGDON...LEBANON...CLEVELAND...TRI-CITY
AIRPORT...BLOOMINGDALE...HILTONS...BLOUNTVILLE...NICKELSVILLE...
COLLINGWOOD...BENHAMS...CASTLEWOOD...HANSONVILLE...HILANDER PARK...
HOLSTON...LINDELL...EMORY-MEADOW VIEW...GLADE SPRING AND ROSEDALE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A
STURDY SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE NEAREST
DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS.

THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT. GET UNDER A
WORKBENCH OR OTHER PIECE OF STURDY FURNITURE. IF NO BASEMENT IS
AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE BUILDING IN AN
INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE BLANKETS OR PILLOWS TO
COVER YOUR BODY AND ALWAYS STAY AWAY FROM WINDOWS.

A TORNADO WATCH REMAINS IN EFFECT UNTIL 100 AM EDT THURSDAY MORNING
FOR SOUTHWEST NORTH CAROLINA AND EAST TENNESSEE. A TORNADO WATCH
ALSO REMAINS IN EFFECT UNTIL 100 AM EDT THURSDAY MORNING FOR
SOUTHWEST VIRGINIA.