Alert archive / Louisiana / Tornado Watches in 2017

Tornado Watch 164

April 26, 20174 states

The Storm Prediction Center issued this tornado watch at Apr 26, 2017, 4:44 PM CDT for 4 states. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Apr 26, 2017, 4:44 PM CDT (21:44 UTC)
Expired
Apr 26, 2017, 9:52 PM CDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
2 in
Strongest gust expected
60 kt
All 72 counties

Arkansas County, AR, Ashley County, AR, Bradley County, AR, Calhoun County, AR, Chicot County, AR, Cleveland County, AR, Columbia County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Jefferson County, AR, Lincoln County, AR, Monroe County, AR, Ouachita County, AR, Prairie County, AR, Union County, AR, Woodruff County, AR, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, Bienville Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Concordia Parish, LA, De Soto Parish, LA, East Carroll Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Bolivar County, MS, Carroll County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Leflore County, MS, Sharkey County, MS, Sunflower County, MS, Warren County, MS, Washington County, MS, Yazoo County, MS, Angelina County, TX, Hardin County, TX, Jasper County, TX, Liberty County, TX, Nacogdoches County, TX, Newton County, TX, Polk County, TX, Sabine County, TX, San Augustine County, TX, San Jacinto County, TX, Shelby County, TX, Trinity County, TX, Tyler County, TX

The radar

The Shreveport radar (KSHV), 136 km from the middle of the area, began a volume at 21:46 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
40%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
70%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
95%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Apr 26, 4:46 PM CDTSevere Thunderstorm WarningLZKJackson, Woodruff44 min
Apr 26, 4:55 PM CDTSevere Thunderstorm WarningHGXPolk20 min
Apr 26, 4:58 PM CDTSevere Thunderstorm WarningLCHJasper, Tyler32 min
Apr 26, 5:00 PM CDTSevere Thunderstorm WarningSHVAngelina33 min
Apr 26, 5:04 PM CDTSevere Thunderstorm WarningLZKBradley, Calhoun, Cleveland41 min
Apr 26, 5:14 PM CDTSevere Thunderstorm WarningSHVBienville, Natchitoches, Red River46 min
Apr 26, 5:18 PM CDTSevere Thunderstorm WarningSHVUnion21 min
Apr 26, 5:25 PM CDTSevere Thunderstorm WarningLCHJasper, Newton, Tyler35 min
Apr 26, 5:26 PM CDTFlash Flood WarningLZKCleveland, Jefferson2 hr
Apr 26, 5:26 PM CDTSevere Thunderstorm WarningSHVBienville, Claiborne, Lincoln49 min
Apr 26, 5:29 PM CDTSevere Thunderstorm WarningSHVGrant, Natchitoches, Sabine, Winn61 min
Apr 26, 5:51 PM CDTSevere Thunderstorm WarningLZKBradley, Cleveland, Drew26 min
Apr 26, 5:57 PM CDTSevere Thunderstorm WarningLCHVernon63 min
Apr 26, 6:02 PM CDTSevere Thunderstorm WarningLZKBradley, Drew29 min
Apr 26, 6:02 PM CDTSevere Thunderstorm WarningSHVLincoln, Ouachita, Union20 min
Apr 26, 6:03 PM CDTSevere Thunderstorm WarningJANAshley, Chicot57 min
Apr 26, 6:11 PM CDTSevere Thunderstorm WarningLZKArkansas, Desha49 min
Apr 26, 6:28 PM CDTSevere Thunderstorm WarningJANChicot62 min
Apr 26, 6:34 PM CDTSevere Thunderstorm WarningLCHJasper, Newton26 min
Apr 26, 6:43 PM CDTSevere Thunderstorm WarningJANChicot62 min
Apr 26, 6:47 PM CDTSevere Thunderstorm WarningLZKDesha28 min
Apr 26, 6:54 PM CDTSevere Thunderstorm WarningLCHBeauregard51 min
Apr 26, 7:06 PM CDTSevere Thunderstorm WarningJANEast Carroll, Franklin, Madison, Richland, West Carroll54 min
Apr 26, 7:31 PM CDTSevere Thunderstorm WarningJANChicot59 min
Apr 26, 7:55 PM CDTSevere Thunderstorm WarningJANEast Carroll, Madison65 min
Apr 26, 7:58 PM CDTSevere Thunderstorm WarningJANHolmes, Humphreys, Leflore, Sunflower62 min
Apr 26, 8:16 PM CDTSevere Thunderstorm WarningJANMadison, Tensas59 min
Apr 26, 8:30 PM CDTSevere Thunderstorm WarningJANCarroll, Grenada, Leflore, Montgomery39 min
Apr 26, 8:45 PM CDTSevere Thunderstorm WarningJANAttala, Hinds, Holmes, Madison, Yazoo60 min
Apr 26, 8:53 PM CDTSevere Thunderstorm WarningJANAttala, Carroll, Holmes, Montgomery67 min
Apr 26, 9:45 PM CDTSevere Thunderstorm WarningJANChoctaw, Grenada, Montgomery, Webster23 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

Shreveport, LA (KBAD), launched 12:00Z, 9.7 hours before the alert went out and 127 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, Shreveport, LA at 12:00Z on 2017-04-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 761 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, Shreveport, LA at 12:00Z on 2017-04-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 324 square meters per square second.19395878Sfc1 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
761 J/kg
Mixed-layer CIN
-435 J/kg
Mixed-layer LCL
770 m above ground
0-6 km bulk shear
34 kt
0-1 km storm-relative helicity
324 m²/s²
0-3 km storm-relative helicity
327 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

932 
WWUS20 KWNS 262142
SEL4  
SPC WW 262142
ARZ000-LAZ000-MSZ000-TXZ000-270400-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 164
NWS Storm Prediction Center Norman OK
445 PM CDT Wed Apr 26 2017

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Southeast Arkansas
  Central and northern Louisiana
  West central Mississippi
  Southeast Texas

* Effective this Wednesday afternoon and evening from 445 PM
  until 1100 PM CDT.

* Primary threats include...
  A couple tornadoes possible
  Scattered damaging wind gusts to 70 mph likely
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible

SUMMARY...Squall line will begin to accelerate eastward through the
evening hours, with some increase in the damaging wind risk
expected.  A couple of tornadoes and large hail will still be
possible, especially with embedded circulations and any
sustained/discrete storms ahead of the line.

The tornado watch area is approximately along and 80 statute miles
east and west of a line from 40 miles north of Greenville MS to 55
miles southwest of Fort Polk LA. For a complete depiction of the
watch see the associated watch outline update (WOUS64 KWNS WOU4).

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 162...WW 163...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean
storm motion vector 25035.

...Thompson

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 25, 10:51 PM CDTMesoscale DiscussionSPCBenton, Boone, Carroll, Madison, Washington54 min
Apr 25, 11:27 PM CDTSevere Thunderstorm WatchSPCBenton, Carroll, Crawford, Franklin, Madison, Sebastian and 1 more7 hr
Apr 26, 1:42 AM CDTMesoscale DiscussionSPCBaxter, Boone, Carroll, Crawford, Franklin, Johnson and 10 more2 hr
Apr 26, 5:37 AM CDTMesoscale DiscussionSPCConway, Crawford, Franklin, Garland, Howard, Johnson and 14 more113 min
Apr 26, 6:00 AM CDTSevere Thunderstorm WatchSPCBaxter, Boone, Carroll, Conway, Crawford, Franklin and 23 more7 hr
Apr 26, 7:29 AM CDTMesoscale DiscussionSPCBaxter, Boone, Carroll, Conway, Crawford, Franklin and 23 more2 hr
Apr 26, 9:39 AM CDTMesoscale DiscussionSPCArkansas, Baxter, Bradley, Calhoun, Clark, Clay and 47 more36 min
Apr 26, 10:08 AM CDTTornado WatchSPCArkansas, Baxter, Bradley, Calhoun, Clark, Clay and 51 more7 hr
Apr 26, 1:05 PM CDTMesoscale DiscussionSPCClark, Columbia, Dallas, Grant, Hempstead, Hot Spring and 9 more85 min
Apr 26, 3:53 PM CDTMesoscale DiscussionSPCClay97 min
Apr 26, 4:23 PM CDTMesoscale DiscussionSPCArkansas, Ashley, Bradley, Calhoun, Chicot, Cleveland and 19 more67 min
Apr 26, 5:02 PM CDTSevere Thunderstorm WatchSPCClay, Craighead, Crittenden, Cross, Greene, Lee and 4 more6 hr
Apr 26, 6:10 PM CDTMesoscale DiscussionSPCMississippi95 min

Nearby

Tornado Watches in Louisiana, 2017Tornado Watches in Arkansas, 2017Tornado Watches in Texas, 2017Every tornado watch in 2017

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.