Alert archive / Arkansas / Tornado Watches in 2018

Tornado Watch 2

January 21, 201843 counties in Arkansas; 17 parishes in Louisiana; 13 counties in Texas

The Storm Prediction Center issued this tornado watch at Jan 21, 2018, 9:59 PM CST for 43 counties in Arkansas; 17 parishes in Louisiana; 13 counties in Texas. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Jan 21, 2018, 9:59 PM CST (03:59 UTC)
Expired
Jan 22, 2018, 4:00 AM CST
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
0.5 in
Strongest gust expected
60 kt
All 73 counties

Baxter County, AR, Boone County, AR, Bradley County, AR, Calhoun County, AR, Clark County, AR, Cleburne County, AR, Cleveland County, AR, Columbia County, AR, Conway County, AR, Dallas County, AR, Faulkner County, AR, Garland County, AR, Grant County, AR, Hempstead County, AR, Hot Spring County, AR, Howard County, AR, Izard County, AR, Jefferson County, AR, Johnson County, AR, Lafayette County, AR, Little River County, AR, Logan County, AR, Lonoke County, AR, Marion County, AR, Miller County, AR, Montgomery County, AR, Nevada County, AR, Newton County, AR, Ouachita County, AR, Perry County, AR, Pike County, AR, Polk County, AR, Pope County, AR, Pulaski County, AR, Saline County, AR, Scott County, AR, Searcy County, AR, Sevier County, AR, Stone County, AR, Union County, AR, Van Buren County, AR, White County, AR, Yell County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Sabine Parish, LA, Union Parish, LA, Webster Parish, LA, Winn Parish, LA, Angelina County, TX, Bowie County, TX, Cass County, TX, Cherokee County, TX, Gregg County, TX, Harrison County, TX, Marion County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX

The radar

The Little Rock radar (KLZK), 65 km from the middle of the area, began a volume at 04:00 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
30%
One or more gusts of 65 knots or more
10%
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
60%

Warnings issued inside it

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

IssuedProductOfficeCountiesLasted
Jan 21, 10:11 PM CSTTornado WarningSHVHoward, Little River, Sevier35 min
Jan 21, 10:31 PM CSTTornado WarningSHVHempstead, Howard, Sevier35 min
Jan 21, 10:34 PM CSTTornado WarningLZKPike28 min
Jan 21, 10:43 PM CSTSevere Thunderstorm WarningSHVSabine, San Augustine47 min
Jan 21, 10:54 PM CSTTornado WarningSHVSabine33 min
Jan 21, 11:00 PM CSTSevere Thunderstorm WarningSHVLittle River, Sevier45 min
Jan 21, 11:02 PM CSTSevere Thunderstorm WarningLZKClark, Garland, Hot Spring, Montgomery, Pike43 min
Jan 21, 11:09 PM CSTTornado WarningSHVCherokee, Rusk, Smith51 min
Jan 21, 11:20 PM CSTTornado WarningLZKGarland, Montgomery, Saline17 min
Jan 21, 11:44 PM CSTTornado WarningSHVGregg, Harrison, Panola, Rusk28 min
Jan 22, 12:24 AM CSTSevere Thunderstorm WarningSHVDe Soto, Natchitoches, Red River, Sabine66 min
Jan 22, 12:28 AM CSTSevere Thunderstorm WarningSHVDe Soto, Natchitoches, Red River, Sabine47 min
Jan 22, 12:52 AM CSTTornado WarningSHVBienville, Jackson, Natchitoches, Red River40 min
Jan 22, 12:53 AM CSTSevere Thunderstorm WarningLZKFaulkner, White37 min
Jan 22, 2:21 AM CSTSevere Thunderstorm WarningSHVLincoln, Ouachita, Union24 min
Jan 22, 2:55 AM CSTTornado WarningSHVGrant, Natchitoches35 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, 4.0 hours before the alert went out and 236 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 2018-01-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 39 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 00:00Z on 2018-01-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 221 square meters per square second.1939587897117Sfc1 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
39 J/kg
Mixed-layer CIN
-55 J/kg
Mixed-layer LCL
970 m above ground
0-6 km bulk shear
47 kt
0-1 km storm-relative helicity
221 m²/s²
0-3 km storm-relative helicity
261 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2

Open this sounding in Storm Lab

The text

As transmitted.

664 
WWUS20 KWNS 220356
SEL2  
SPC WW 220356
ARZ000-LAZ000-TXZ000-221000-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 2
NWS Storm Prediction Center Norman OK
1000 PM CST Sun Jan 21 2018

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Western and central Arkansas
  Northwestern Louisiana
  Extreme northeastern Texas

* Effective this Sunday night and Monday morning from 1000 PM
  until 400 AM CST.

* Primary threats include...
  A couple tornadoes possible
  Isolated damaging wind gusts to 70 mph possible

SUMMARY...Ongoing broken band of supercells will continue to spread
eastward overnight, with some tendency to grow into more linear
structures with time as the cold front eventually overtakes the warm
sector storms.  A couple of tornadoes and damaging gusts will be
possible with the persisting supercells and embedded circulations
within line segments.

The tornado watch area is approximately along and 55 statute miles
east and west of a line from 25 miles northeast of Flippin AR to 70
miles south southeast of Longview TX. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU2).

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 1...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 0.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 400. Mean
storm motion vector 24045.

...Thompson

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jan 21, 6:25 PM CSTMesoscale DiscussionSPCClark, Crawford, Franklin, Garland, Hempstead, Hot Spring and 15 more2 hr
Jan 21, 9:35 PM CSTMesoscale DiscussionSPCBaxter, Boone, Calhoun, Carroll, Clark, Cleburne and 45 more115 min
Jan 22, 1:16 AM CSTMesoscale DiscussionSPCAshley, Baxter, Bradley, Calhoun, Clark, Cleburne and 26 more119 min

Nearby

Tornado Watches in Arkansas, 2018Tornado Watches in Louisiana, 2018Tornado Watches in Texas, 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.