Alert archive / Arkansas / Mesoscale Discussions in 2021
Mesoscale Discussion 447
The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 8:52 AM CDT for 23 counties in Arkansas; 7 counties in Missouri. It was in force for 113 min.
The area
The outline as issued.
The facts
- Issued
- Apr 28, 2021, 8:52 AM CDT (13:52 UTC)
- Expired
- Apr 28, 2021, 10:45 AM CDT
- In force
- 113 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 30 counties
Baxter County, AR, Boone County, AR, Clay County, AR, Cleburne County, AR, Conway County, AR, Craighead County, AR, Fulton County, AR, Greene County, AR, Independence County, AR, Izard County, AR, Jackson County, AR, Johnson County, AR, Lawrence County, AR, Marion County, AR, Mississippi County, AR, Newton County, AR, Poinsett County, AR, Pope County, AR, Randolph County, AR, Searcy County, AR, Sharp County, AR, Stone County, AR, Van Buren County, AR, Butler County, MO, Dunklin County, MO, Howell County, MO, Oregon County, MO, Ozark County, MO, Ripley County, MO, Taney County, MO
The radar
The Little Rock radar (KLZK), 135 km from the middle of the area, began a volume at 13:54 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.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Little Rock, AR (KLZK), launched 12:00Z, 1.9 hours before the alert went out and 201 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
- 845 J/kg
- Mixed-layer CIN
- -8 J/kg
- Mixed-layer LCL
- 593 m above ground
- 0-6 km bulk shear
- 48 kt
- 0-1 km storm-relative helicity
- 78 m²/s²
- 0-3 km storm-relative helicity
- 122 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 1.7
The text
As transmitted.
989
ACUS11 KWNS 281352
SWOMCD
SPC MCD 281352
MOZ000-ARZ000-281545-
Mesoscale Discussion 0447
NWS Storm Prediction Center Norman OK
0852 AM CDT Wed Apr 28 2021
Areas affected...Portions of northern AR and southern MO
Concerning...Severe potential...Watch possible
Valid 281352Z - 281545Z
Probability of Watch Issuance...40 percent
SUMMARY...Some severe threat may continue this morning with a
cluster of storms moving eastward, including the potential for
damaging winds and a tornado. Watch issuance is possible.
DISCUSSION...A loosely organized cluster of storms has developed
this morning across northwestern AR and southwestern MO. VWPs from
KLZK/KSRX indicate around 30-35 kt of 0-1 km shear is present, along
with a favorable veering/strengthening wind profile with height
through mid levels. Low-level rotation has been noted with a couple
circulations within the line. An isolated tornado threat may
continue through the morning across parts of southern MO and
northern AR where rich low-level moisture, a weakly unstable
airmass, and strong shear at low levels can support surface-based
storms. Given the linear nature of the ongoing convection, damaging
winds may be the primary severe threat. Filtered diurnal heating
through a cloud deck downstream of this ongoing activity should
support a gradual increase in boundary-layer instability over the
next couple of hours. Although convective evolution remains somewhat
uncertain this morning, downstream watch issuance may be needed if
storms maintain their current intensity.
..Gleason/Hart.. 04/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PAH...MEG...LZK...SGF...
LAT...LON 35369122 35249244 35359364 35959328 36859321 36929183
36849004 36178978 35549013 35369122SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 28, 3:01 AM CDT | Tornado Watch | SPC | Benton, Carroll, Crawford, Madison, Washington | 7 hr |
| Apr 28, 6:35 AM CDT | Mesoscale Discussion | SPC | Washington | 3 hr |
| Apr 28, 9:25 AM CDT | Mesoscale Discussion | SPC | Carroll, Crawford, Madison, Washington | 65 min |
| Apr 28, 10:56 AM CDT | Mesoscale Discussion | SPC | Fulton | 64 min |
| Apr 28, 6:01 PM CDT | Mesoscale Discussion | SPC | Crawford, Franklin, Howard, Logan, Montgomery, Polk and 3 more | 119 min |
| Apr 28, 9:33 AM CDT | Tornado Watch | SPC | Christian, Douglas, Howell, Oregon, Ozark, Shannon and 4 more | 4 hr |
| Apr 28, 12:33 PM CDT | Mesoscale Discussion | SPC | Bollinger, Butler, Cape Girardeau, Carter, Madison, Mississippi and 7 more | 57 min |
| Apr 28, 12:40 PM CDT | Severe Thunderstorm Watch | SPC | Bollinger, Butler, Cape Girardeau, Carter, Mississippi, New Madrid and 4 more | 7 hr |
| Apr 28, 3:29 PM CDT | Mesoscale Discussion | SPC | Bollinger, Butler, Cape Girardeau, Mississippi, New Madrid, Scott and 1 more | 91 min |
| Apr 28, 5:25 PM CDT | Mesoscale Discussion | SPC | Mississippi | 2 hr |
Nearby
Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Missouri, 2021Every mesoscale discussion in 2021
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.