Alert archive / Arkansas / Severe Thunderstorm Watches in 2018

Severe Thunderstorm Watch 446

December 27, 20188 counties in Arkansas; 7 parishes in Louisiana; Bowie County, Cass County, Texas

The Storm Prediction Center issued this severe thunderstorm watch at Dec 27, 2018, 12:02 AM CST for 8 counties in Arkansas; 7 parishes in Louisiana; Bowie County, Cass County, Texas. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Dec 27, 2018, 12:02 AM CST (06:02 UTC)
Expired
Dec 27, 2018, 5:00 AM CST
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
0.5 in
Strongest gust expected
60 kt

Counties Columbia County, AR, Hempstead County, AR, Howard County, AR, Lafayette County, AR, Little River County, AR, Miller County, AR, Nevada County, AR, Sevier County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Red River Parish, LA, Webster Parish, LA, Bowie County, TX, Cass County, TX

The radar

The Shreveport radar (KSHV), 85 km from the middle of the area, began a volume at 06:07 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
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
20%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
5%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
40%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Dec 27, 12:10 AM CSTTornado WarningSHVCass, Gregg, Harrison, Marion, Upshur50 min
Dec 27, 12:24 AM CSTTornado WarningSHVMiller31 min
Dec 27, 12:53 AM CSTSevere Thunderstorm WarningSHVLafayette, Miller52 min
Dec 27, 1:23 AM CSTTornado WarningSHVBossier, Caddo37 min
Dec 27, 1:30 AM CSTSevere Thunderstorm WarningSHVLafayette, Miller60 min
Dec 27, 1:37 AM CSTTornado WarningSHVBossier, Caddo38 min
Dec 27, 1:54 AM CSTTornado WarningSHVColumbia, Lafayette25 min
Dec 27, 2:07 AM CSTTornado WarningSHVCaddo, De Soto27 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 00:00Z, 6.0 hours before the alert went out and 79 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 00:00Z on 2018-12-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 00:00Z on 2018-12-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 280 square meters per square second.1939587897Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
836 m above ground
0-6 km bulk shear
51 kt
0-1 km storm-relative helicity
280 m²/s²
0-3 km storm-relative helicity
510 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Dec 27, 1:39 AM CSTMesoscale DiscussionSPCCalhoun, Columbia, Hempstead, Lafayette, Nevada, Ouachita and 1 more2 hr
Dec 26, 11:40 PM CSTMesoscale DiscussionSPCBossier, Caddo, De Soto2 hr
Dec 27, 3:09 AM CSTMesoscale DiscussionSPCAllen, Beauregard, Calcasieu, Cameron, Jefferson Davis, Vernon2 hr
Dec 27, 3:43 AM CSTTornado WatchSPCAcadia, Allen, Beauregard, Calcasieu, Caldwell, Cameron and 10 more10 hr
Dec 27, 7:12 AM CSTMesoscale DiscussionSPCAcadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 11 more2 hr
Dec 27, 9:00 AM CSTMesoscale DiscussionSPCAvoyelles, Catahoula, Concordia, East Baton Rouge, East Feliciana, Iberville and 6 more60 min
Dec 27, 9:29 AM CSTTornado WatchSPCAscension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 27 more9 hr
Dec 27, 1:50 PM CSTMesoscale DiscussionSPCAscension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 19 more85 min
Dec 26, 7:13 PM CSTMesoscale DiscussionSPCBell, Bosque, Collin, Cooke, Dallas, Delta and 22 more2 hr
Dec 26, 8:51 PM CSTMesoscale DiscussionSPCAtascosa, Bandera, Bastrop, Bexar, Blanco, Caldwell and 18 more114 min
Dec 26, 9:34 PM CSTTornado WatchSPCAnderson, Angelina, Brazos, Burleson, Cherokee, Falls and 29 more6 hr

Nearby

Severe Thunderstorm Watches in Arkansas, 2018Severe Thunderstorm Watches in Louisiana, 2018Severe Thunderstorm Watches in Texas, 2018Every severe thunderstorm 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.