Alert archive / Alabama / Tornado Watches in 2018

Tornado Watch 208

June 23, 201815 counties in Alabama; 5 counties in Tennessee

The Storm Prediction Center issued this tornado watch at Jun 23, 2018, 5:40 PM CDT for 15 counties in Alabama; 5 counties in Tennessee. It was in force for 4 hr.

The area

The outline as issued.

The facts

Issued
Jun 23, 2018, 5:40 PM CDT (22:40 UTC)
Expired
Jun 23, 2018, 10:00 PM CDT
In force
4 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.5 in
Strongest gust expected
50 kt

Counties Blount County, AL, Colbert County, AL, Cullman County, AL, Fayette County, AL, Franklin County, AL, Lamar County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Walker County, AL, Winston County, AL, Giles County, TN, Lawrence County, TN, Lincoln County, TN, Moore County, TN, Wayne County, TN

The radar

The Columbus AFB radar (KGWX), 113 km from the middle of the area, began a volume at 22:42 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
30%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
20%
One or more gusts of 65 knots or more
5%
Ten or more severe hail reports
20%
One or more hailstones of 2 inches or more
10%
Six or more combined severe hail and wind reports
40%

Warnings issued inside it

15 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Jun 23, 5:45 PM CDTTornado WarningHUNColbert, Franklin, Lawrence30 min
Jun 23, 6:32 PM CDTSevere Thunderstorm WarningHUNFranklin13 min
Jun 23, 6:33 PM CDTSevere Thunderstorm WarningBMXWinston27 min
Jun 23, 6:35 PM CDTSevere Thunderstorm WarningBMXFayette, Lamar25 min
Jun 23, 7:45 PM CDTSevere Thunderstorm WarningBMXFayette, Lamar30 min
Jun 23, 7:46 PM CDTSevere Thunderstorm WarningOHXWayne29 min
Jun 23, 8:01 PM CDTTornado WarningOHXWayne29 min
Jun 23, 8:05 PM CDTTornado WarningHUNLauderdale25 min
Jun 23, 8:14 PM CDTSevere Thunderstorm WarningBMXFayette31 min
Jun 23, 8:29 PM CDTSevere Thunderstorm WarningHUNLauderdale31 min
Jun 23, 8:55 PM CDTTornado WarningOHXLawrence, Wayne35 min
Jun 23, 9:28 PM CDTTornado WarningOHXLawrence, Wayne32 min
Jun 23, 9:37 PM CDTSevere Thunderstorm WarningHUNLauderdale23 min
Jun 23, 9:38 PM CDTFlash Flood WarningOHXLawrence, Wayne3 hr
Jun 23, 9:58 PM CDTSevere Thunderstorm WarningHUNLauderdale14 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Birmingham, AL (KBMX), launched 12:00Z, 10.7 hours before the alert went out and 165 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Birmingham, AL at 12:00Z on 2018-06-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1359 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Birmingham, AL at 12:00Z on 2018-06-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 164 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
1359 J/kg
Mixed-layer CIN
-34 J/kg
Mixed-layer LCL
599 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
164 m²/s²
0-3 km storm-relative helicity
198 m²/s²
Significant tornado parameter
0.8
Supercell composite
5.8

Open this sounding in Storm Lab

The text

As transmitted.

309 
WWUS20 KWNS 232238
SEL8  
SPC WW 232238
ALZ000-TNZ000-240300-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 208
NWS Storm Prediction Center Norman OK
540 PM CDT Sat Jun 23 2018

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Northern Alabama
  Southern Middle Tennessee

* Effective this Saturday afternoon and evening from 540 PM until
  1000 PM CDT.

* Primary threats include...
  A couple tornadoes possible
  Isolated damaging wind gusts to 60 mph possible
  Isolated large hail events to 1.5 inches in diameter possible

SUMMARY...A couple supercells have developed across northwest
Alabama and may persist for a few hours along a remnant outflow
boundary. Although coverage should be limited, all severe hazards
are possible.

The tornado watch area is approximately along and 50 statute miles
north and south of a line from 45 miles southwest of Muscle Shoals
AL to 30 miles east of Huntsville AL. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU8).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 205...WW 206...WW 207...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1.5 inches. Extreme turbulence and surface wind
gusts to 50 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 27025.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jun 23, 7:17 AM CDTMesoscale DiscussionSPCBlount, Colbert, Cullman, Fayette, Franklin, Jefferson and 6 more118 min
Jun 23, 10:32 AM CDTMesoscale DiscussionSPCCherokee, Colbert, Cullman, DeKalb, Etowah, Franklin and 8 more88 min
Jun 23, 11:09 AM CDTSevere Thunderstorm WatchSPCDeKalb, Jackson, Limestone, Madison, Marshall, Morgan4 hr
Jun 23, 4:50 PM CDTMesoscale DiscussionSPCColbert, Franklin, Lamar, Lauderdale, Marion115 min

Nearby

Tornado Watches in Alabama, 2018Tornado Watches in Tennessee, 2018Every tornado watch in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.