Alert archive / Arkansas / Severe Thunderstorm Watches in 2017

Severe Thunderstorm Watch 507

October 21, 20174 states

The Storm Prediction Center issued this severe thunderstorm watch at Oct 21, 2017, 11:56 PM CDT for 4 states. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: Oct 21, 2017, 11:56 PM CDT (04:56 UTC)
Expired: Oct 22, 2017, 7:00 AM CDT
In force: 7 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

All 77 counties

Arkansas County, AR, Baxter County, AR, Benton County, AR, Boone County, AR, Bradley County, AR, Calhoun County, AR, Carroll County, AR, Clark County, AR, Cleburne County, AR, Cleveland County, AR, Columbia County, AR, Conway County, AR, Crawford County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Faulkner County, AR, Franklin County, AR, Fulton County, AR, Garland County, AR, Grant County, AR, Hempstead County, AR, Hot Spring County, AR, Howard County, AR, Independence County, AR, Izard County, AR, Jackson County, AR, Jefferson County, AR, Johnson County, AR, Lafayette County, AR, Lincoln County, AR, Little River County, AR, Logan County, AR, Lonoke County, AR, Madison County, AR, Marion County, AR, Miller County, AR, Monroe 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, Prairie County, AR, Pulaski County, AR, Saline County, AR, Scott County, AR, Searcy County, AR, Sebastian County, AR, Sevier County, AR, Sharp County, AR, Stone County, AR, Van Buren County, AR, Washington County, AR, White County, AR, Woodruff County, AR, Yell County, AR, Douglas County, MO, Howell County, MO, Laclede County, MO, Ozark County, MO, Texas County, MO, Wright County, MO, McCurtain County, OK, Bowie County, TX, Camp County, TX, Cass County, TX, Franklin County, TX, Marion County, TX, Morris County, TX, Red River County, TX, Titus County, TX, Upshur County, TX, Wood County, TX

The radar

The Western Arkansas radar (KSRX), 113 km from the middle of the area, began a volume at 04:56 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: 2%
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

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

Issued	Product	Office	Counties	Lasted
Oct 22, 12:41 AM CDT	Severe Thunderstorm Warning	TSA	Crawford, Washington	34 min
Oct 22, 12:46 AM CDT	Severe Thunderstorm Warning	TSA	Crawford, Sebastian	29 min
Oct 22, 1:01 AM CDT	Severe Thunderstorm Warning	LZK	Logan, Polk, Scott	59 min
Oct 22, 1:08 AM CDT	Severe Thunderstorm Warning	TSA	Crawford, Franklin, Madison, Sebastian, Washington	37 min
Oct 22, 1:13 AM CDT	Severe Thunderstorm Warning	SGF	Christian, Douglas, Greene, Webster	47 min
Oct 22, 1:26 AM CDT	Severe Thunderstorm Warning	SGF	Ozark, Taney	64 min
Oct 22, 1:34 AM CDT	Severe Thunderstorm Warning	LZK	Johnson, Logan	56 min
Oct 22, 1:42 AM CDT	Severe Thunderstorm Warning	TSA	Crawford, Franklin, Madison, Sebastian, Washington	33 min
Oct 22, 1:48 AM CDT	Severe Thunderstorm Warning	LZK	Logan, Montgomery, Scott, Yell	57 min
Oct 22, 1:50 AM CDT	Severe Thunderstorm Warning	SGF	Douglas, Laclede, Wright	55 min
Oct 22, 2:15 AM CDT	Severe Thunderstorm Warning	LZK	Conway, Garland, Johnson, Logan, Perry, Pope and 1 more	46 min
Oct 22, 2:23 AM CDT	Severe Thunderstorm Warning	SGF	Ozark	67 min
Oct 22, 2:48 AM CDT	Severe Thunderstorm Warning	LZK	Conway, Faulkner, Garland, Perry, Pope, Pulaski and 2 more	57 min
Oct 22, 3:10 AM CDT	Severe Thunderstorm Warning	LZK	Cleburne, Searcy, Stone, Van Buren	50 min
Oct 22, 3:11 AM CDT	Severe Thunderstorm Warning	SGF	Dent, Howell, Oregon, Shannon, Texas	64 min
Oct 22, 3:12 AM CDT	Severe Thunderstorm Warning	LZK	Garland, Grant, Hot Spring, Saline	48 min
Oct 22, 3:29 AM CDT	Severe Thunderstorm Warning	LZK	Cleburne, Faulkner, Van Buren, White	29 min
Oct 22, 4:23 AM CDT	Severe Thunderstorm Warning	LZK	Lonoke, Monroe, Prairie, White, Woodruff	41 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

Springfield, MO (KSGF), launched 00:00Z, 4.9 hours before the alert went out and 150 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 700 J/kg
Mixed-layer CIN: -128 J/kg
Mixed-layer LCL: 1064 m above ground
0-6 km bulk shear: 37 kt
0-1 km storm-relative helicity: 157 m²/s²
0-3 km storm-relative helicity: 169 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.4

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 21, 8:34 PM CDT	Mesoscale Discussion	SPC	Benton, Washington	86 min
Oct 21, 10:42 PM CDT	Mesoscale Discussion	SPC	Benton, Crawford, Franklin, Howard, Little River, Logan and 6 more	93 min
Oct 22, 1:44 AM CDT	Mesoscale Discussion	SPC	Baxter, Boone, Carroll, Clark, Conway, Franklin and 24 more	91 min
Oct 22, 4:57 AM CDT	Mesoscale Discussion	SPC	Arkansas, Ashley, Bradley, Calhoun, Clay, Cleveland and 29 more	93 min
Oct 21, 8:10 PM CDT	Mesoscale Discussion	SPC	Barry, Barton, Bates, Benton, Caldwell, Camden and 40 more	95 min
Oct 21, 10:06 PM CDT	Severe Thunderstorm Watch	SPC	Barry, Barton, Cedar, Christian, Dade, Dallas and 12 more	5 hr
Oct 21, 7:24 PM CDT	Tornado Watch	SPC	Adair, Atoka, Bryan, Carter, Cherokee, Choctaw and 33 more	7 hr
Oct 21, 7:53 PM CDT	Severe Thunderstorm Watch	SPC	Brown, Callahan, Coleman, Collin, Comanche, Cooke and 28 more	6 hr
Oct 21, 10:09 PM CDT	Mesoscale Discussion	SPC	Callahan, Collin, Cooke, Dallas, Denton, Eastland and 14 more	96 min

Nearby

Severe Thunderstorm Watches in Arkansas, 2017 Severe Thunderstorm Watches in Texas, 2017 Severe Thunderstorm Watches in Missouri, 2017 Every severe thunderstorm 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.