Alert archive / Arkansas / Severe Thunderstorm Watches in 2020
Severe Thunderstorm Watch 477
The Storm Prediction Center issued this severe thunderstorm watch at Aug 31, 2020, 6:20 AM CDT for 28 counties in Arkansas; LeFlore County, Sequoyah County, Oklahoma. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 31, 2020, 6:20 AM CDT (11:20 UTC)
- Expired
- Aug 31, 2020, 10:42 AM CDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 65 kt
All 30 counties
Arkansas County, AR, Clark County, AR, Cleveland County, AR, Conway County, AR, Crawford County, AR, Dallas County, AR, Faulkner County, AR, Franklin County, AR, Garland County, AR, Grant County, AR, Hot Spring County, AR, Jefferson County, AR, Johnson County, AR, Lincoln County, AR, Logan County, AR, Lonoke County, AR, Monroe County, AR, Montgomery 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, Sebastian County, AR, Yell County, AR, LeFlore County, OK, Sequoyah County, OK
The radar
The Western Arkansas radar (KSRX), 89 km from the middle of the area, began a volume at 11:20 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
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
10 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 31, 6:57 AM CDT | Severe Thunderstorm Warning | LZK | Logan, Yell | 48 min |
| Aug 31, 7:01 AM CDT | Severe Thunderstorm Warning | TSA | Crawford, Franklin, Sebastian | 44 min |
| Aug 31, 7:07 AM CDT | Severe Thunderstorm Warning | LZK | Logan, Scott | 38 min |
| Aug 31, 7:09 AM CDT | Flash Flood Warning | LZK | Logan, Scott | 4 hr |
| Aug 31, 7:21 AM CDT | Severe Thunderstorm Warning | LZK | Garland, Perry, Saline, Yell | 20 min |
| Aug 31, 7:26 AM CDT | Flash Flood Warning | LZK | Logan, Yell | 4 hr |
| Aug 31, 7:30 AM CDT | Flash Flood Warning | TSA | Sebastian | 4 hr |
| Aug 31, 8:50 AM CDT | Flash Flood Warning | LZK | Garland, Hot Spring, Montgomery, Perry, Saline, Yell | 3 hr |
| Aug 31, 9:02 AM CDT | Flash Flood Warning | TSA | Crawford, Franklin, Sebastian | 3 hr |
| Aug 31, 9:53 AM CDT | Flash Flood Warning | LZK | Grant, Hot Spring, Saline | 3 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
Springfield, MO (KSGF), launched 00:00Z, 11.3 hours before the alert went out and 216 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.
- Mixed-layer CAPE
- 922 J/kg
- Mixed-layer CIN
- -4 J/kg
- Mixed-layer LCL
- 693 m above ground
- 0-6 km bulk shear
- 36 kt
- 0-1 km storm-relative helicity
- 39 m²/s²
- 0-3 km storm-relative helicity
- 73 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 2.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 31, 4:18 AM CDT | Mesoscale Discussion | SPC | Benton, Crawford, Scott, Sebastian, Washington | 117 min |
| Aug 31, 9:38 AM CDT | Mesoscale Discussion | SPC | Arkansas, Clark, Cleveland, Dallas, Grant, Hot Spring and 6 more | 97 min |
| Aug 31, 12:16 PM CDT | Mesoscale Discussion | SPC | Clay, Craighead, Crittenden, Greene, Mississippi, Phillips | 89 min |
| Aug 31, 3:34 PM CDT | Mesoscale Discussion | SPC | Caddo, Canadian, Carter, Cleveland, Comanche, Cotton and 31 more | 86 min |
| Aug 31, 3:53 PM CDT | Severe Thunderstorm Watch | SPC | Caddo, Canadian, Carter, Cleveland, Comanche, Cotton and 30 more | 10 hr |
| Aug 31, 6:13 PM CDT | Mesoscale Discussion | SPC | Caddo, Canadian, Cleveland, Comanche, Cotton, Craig and 17 more | 92 min |
Nearby
Severe Thunderstorm Watches in Arkansas, 2020Severe Thunderstorm Watches in Oklahoma, 2020Every severe thunderstorm watch in 2020
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.