Alert archive / North Carolina / Mesoscale Discussions in 2021
Mesoscale Discussion 349
The Storm Prediction Center issued this mesoscale discussion at Apr 9, 2021, 6:23 PM EDT for 20 counties in North Carolina; 15 counties in Virginia. It was in force for 97 min.
The area
The outline as issued.
The facts
- Issued
- Apr 9, 2021, 6:23 PM EDT (22:23 UTC)
- Expired
- Apr 9, 2021, 8:00 PM EDT
- In force
- 97 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 78
All 35 counties
Bertie County, NC, Camden County, NC, Caswell County, NC, Chowan County, NC, Currituck County, NC, Edgecombe County, NC, Franklin County, NC, Gates County, NC, Granville County, NC, Halifax County, NC, Hertford County, NC, Martin County, NC, Nash County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Person County, NC, Rockingham County, NC, Vance County, NC, Warren County, NC, Brunswick County, VA, City of Chesapeake, VA, City of Danville, VA, City of Emporia, VA, City of Franklin, VA, City of Portsmouth, VA, City of Suffolk, VA, Greensville County, VA, Halifax County, VA, Isle of Wight County, VA, Lunenburg County, VA, Mecklenburg County, VA, Pittsylvania County, VA, Southampton County, VA, Sussex County, VA
The radar
The Raleigh/Durham radar (KRAX), 95 km from the middle of the area, began a volume at 22:28 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 nearest sounding before it
Roanoke, VA (KRNK), launched 12:00Z, 10.4 hours before the alert went out and 156 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
- 132 J/kg
- Mixed-layer CIN
- -77 J/kg
- Mixed-layer LCL
- 654 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 182 m²/s²
- 0-3 km storm-relative helicity
- 199 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.2
The text
As transmitted.
845
ACUS11 KWNS 092223
SWOMCD
SPC MCD 092223
NCZ000-VAZ000-100000-
Mesoscale Discussion 0349
NWS Storm Prediction Center Norman OK
0523 PM CDT Fri Apr 09 2021
Areas affected...Portions of southern Virginia into northern North
Carolina
Concerning...Severe Thunderstorm Watch 78...
Valid 092223Z - 100000Z
The severe weather threat for Severe Thunderstorm Watch 78
continues.
SUMMARY...The severe threat continues across Severe Thunderstorm
Watch #078. Large hail and damaging winds are expected to be the
primary threats, with severe potential likely persisting for at
least a few more hours.
DISCUSSION...Mature semi-discrete multicellular clusters and
transient supercells are straddling the VA/NC border, with MRMS
Mosaic radar data showing MESH cores within the 1-1.5 inch range
with 50 dBZ cell cores exceeding 35 kft. 20Z Mesoanalysis provided
mid-level lapse rates show a 7-8 C/km plume advecting eastward over
the Carolina Piedmont, atop widespread 8-8.5 C/km 0-3 km lapse rates
given the presence of a dry boundary layer. The deep-layer steep
lapse rates will continue to support a large hail threat with the
more mature storms. Though the deep-layer flow below 500 mb is
relatively weak, the dry boundary layer will foster ample
microphysical cooling, with damaging outflow gusts possible. While
storm outflow will have a tendency to locally undercut storms and
reduce their longevity to a degree, the outflow will support
localized lift for the initiation of newer, intense updrafts. As
such, large hail and gusty wind threats are expected to persist for
at least a few more hours, with a gradual weakening trend expected
with the onset of nocturnal cooling.
..Squitieri.. 04/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...MHX...RAH...RNK...
LAT...LON 36497985 36937938 36977858 36997736 37007642 36587582
36157593 35907650 35737718 35897828 36187927 36347996
36497985SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 9, 1:37 PM EDT | Mesoscale Discussion | SPC | Alleghany, Ashe, Stokes, Surry, Warren, Wilkes | 113 min |
| Apr 9, 3:38 PM EDT | Severe Thunderstorm Watch | SPC | Bertie, Camden, Caswell, Chowan, Edgecombe, Franklin and 14 more | 7 hr |
Nearby
Mesoscale Discussions in North Carolina, 2021Mesoscale Discussions in Virginia, 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.