Alert archive / Arkansas / Tornado Watches in 2018

Tornado Watch 417

October 31, 201825 counties in Arkansas

The Storm Prediction Center issued this tornado watch at Oct 31, 2018, 4:11 PM CDT for 25 counties in Arkansas. It was in force for 8 hr.

The area

The outline as issued.

The facts

Issued: Oct 31, 2018, 4:11 PM CDT (21:11 UTC)
Expired: Nov 1, 2018, 12:00 AM CDT
In force: 8 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1.5 in
Strongest gust expected: 60 kt

All 25 counties

Arkansas County, AR, Bradley County, AR, Calhoun County, AR, Clark County, AR, Cleveland County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Faulkner County, AR, Garland County, AR, Grant County, AR, Hot Spring County, AR, Jefferson County, AR, Lincoln County, AR, Lonoke County, AR, Monroe County, AR, Montgomery County, AR, Ouachita County, AR, Perry County, AR, Pike County, AR, Prairie County, AR, Pulaski County, AR, Saline County, AR, White County, AR, Woodruff County, AR

The radar

The Little Rock radar (KLZK), 104 km from the middle of the area, began a volume at 21:10 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: 40%
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: 20%
Six or more combined severe hail and wind reports: 70%

Warnings issued inside it

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

Issued	Product	Office	Counties	Lasted
Oct 31, 4:32 PM CDT	Flash Flood Warning	LZK	Garland, Montgomery, Pike, Polk, Scott, Yell	3 hr
Oct 31, 6:21 PM CDT	Flash Flood Warning	LZK	Cleburne, Independence, Jackson, Lawrence, Sharp, White	3 hr
Oct 31, 7:51 PM CDT	Flash Flood Warning	LZK	Faulkner, Garland, Grant, Perry, Pulaski, Saline	4 hr

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, 9.2 hours before the alert went out and 199 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: 273 J/kg
Mixed-layer CIN: -31 J/kg
Mixed-layer LCL: 723 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 187 m²/s²
0-3 km storm-relative helicity: 155 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.4

Open this sounding in Storm Lab

The text

As transmitted.

334 
WWUS20 KWNS 312108
SEL7  
SPC WW 312108
ARZ000-010500-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 417
NWS Storm Prediction Center Norman OK
410 PM CDT Wed Oct 31 2018

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  Central and southeastern Arkansas

* Effective this Wednesday afternoon from 410 PM until Midnight
  CDT.

* Primary threats include...
  A couple tornadoes possible
  Scattered damaging wind gusts to 70 mph possible
  Scattered large hail events to 1.5 inches in diameter possible

SUMMARY...Thunderstorms will increase through the evening from
southwestern into central Arkansas, and then storms will spread
eastward through the early overnight hours.  The storm environment
will gradually become more favorable for rotating storms, with an
attendant threat for a couple of tornadoes, damaging winds, and
isolated large hail.

The tornado watch area is approximately along and 75 statute miles
east and west of a line from 70 miles south southwest of Hot Springs
AR to 45 miles northeast of Little Rock AR. For a complete depiction
of the watch see the associated watch outline update (WOUS64 KWNS
WOU7).

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 416...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
storm motion vector 24035.

...Thompson

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 31, 3:02 PM CDT	Tornado Watch	SPC	Columbia, Hempstead, Howard, Lafayette, Little River, Miller and 2 more	9 hr
Oct 31, 3:55 PM CDT	Mesoscale Discussion	SPC	Arkansas, Bradley, Calhoun, Clark, Cleveland, Cross and 18 more	95 min
Oct 31, 6:14 PM CDT	Mesoscale Discussion	SPC	Columbia, Hempstead, Lafayette, Little River, Miller, Nevada and 1 more	61 min

Nearby

Tornado Watches in Arkansas, 2018 Every 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.