Alert archive / North Carolina / Mesoscale Discussions in 2021

Mesoscale Discussion 1776

September 22, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Sep 22, 2021, 2:44 PM EDT for 4 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Sep 22, 2021, 2:44 PM EDT (18:44 UTC)
Expired: Sep 22, 2021, 5:15 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 107 counties

Alamance County, NC, Alexander County, NC, Alleghany County, NC, Anson County, NC, Ashe County, NC, Burke County, NC, Cabarrus County, NC, Caldwell County, NC, Caswell County, NC, Catawba County, NC, Chatham County, NC, Cleveland County, NC, Davidson County, NC, Davie County, NC, Durham County, NC, Forsyth County, NC, Gaston County, NC, Granville County, NC, Guilford County, NC, Iredell County, NC, Lee County, NC, Lincoln County, NC, McDowell County, NC, Mecklenburg County, NC, Montgomery County, NC, Moore County, NC, Orange County, NC, Person County, NC, Polk County, NC, Randolph County, NC, Richmond County, NC, Rockingham County, NC, Rowan County, NC, Rutherford County, NC, Scotland County, NC, Stanly County, NC, Stokes County, NC, Surry County, NC, Union County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Aiken County, SC, Anderson County, SC, Bamberg County, SC, Barnwell County, SC, Calhoun County, SC, Cherokee County, SC, Chester County, SC, Chesterfield County, SC, Clarendon County, SC, Darlington County, SC, Dorchester County, SC, Edgefield County, SC, Fairfield County, SC, Greenville County, SC, Greenwood County, SC, Kershaw County, SC, Lancaster County, SC, Laurens County, SC, Lee County, SC, Lexington County, SC, Marlboro County, SC, Newberry County, SC, Orangeburg County, SC, Pickens County, SC, Richland County, SC, Saluda County, SC, Spartanburg County, SC, Sumter County, SC, Union County, SC, York County, SC, Alleghany County, VA, Amherst County, VA, Appomattox County, VA, Bath County, VA, Bedford County, VA, Botetourt County, VA, Campbell County, VA, Carroll County, VA, Charlotte County, VA, City of Buena Vista, VA, City of Covington, VA, City of Danville, VA, City of Galax, VA, City of Lexington, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, Craig County, VA, Floyd County, VA, Franklin County, VA, Giles County, VA, Grayson County, VA, Halifax County, VA, Henry County, VA, Montgomery County, VA, Nelson County, VA, Patrick County, VA, Pittsylvania County, VA, Pulaski County, VA, Roanoke County, VA, Rockbridge County, VA, Wythe County, VA, Monroe County, WV

The radar

The Raleigh/Durham radar (KRAX), 149 km from the middle of the area, began a volume at 18:47 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

Greensboro/Hi Pt, NC (KGSO), launched 12:00Z, 6.7 hours before the alert went out and 56 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: 410 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 516 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 77 m²/s²
0-3 km storm-relative helicity: 117 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

320 
ACUS11 KWNS 221844
SWOMCD
SPC MCD 221844 
VAZ000-NCZ000-SCZ000-WVZ000-TNZ000-222115-

Mesoscale Discussion 1776
NWS Storm Prediction Center Norman OK
0144 PM CDT Wed Sep 22 2021

Areas affected...portions of central into northern South
Carolina...western North Carolina...western Virginia

Concerning...Severe potential...Watch unlikely 

Valid 221844Z - 222115Z

Probability of Watch Issuance...20 percent

SUMMARY...A couple damaging gusts may accompany the stronger storms
through the remainder of the afternoon. A WW issuance is not
anticipated given the isolated, brief nature of the severe threat.

DISCUSSION...A broad confluence zone, delineating the surface cold
front/lee trough axis, is progressing across the central/southern
Appalachians, accompanied primarily by heavier rain bands. However,
adequate diurnal heating in advance of this confluence band has
supported surface temperatures reaching near 80 F with 70+ F
dewpoints, contributing to 1000-2000 J/kg MLCAPE in the absence of
appreciable lapse rates (per 18Z mesoanalysis). 

With continued surface heating, and modest deep-layer ascent from
the approaching mid-level trough overspreading the surface
lee-trough axis, some convective intensification is expected along
the aforementioned confluence zone. However,
unidirectional/meridional tropospheric flow suggests that vertical
shear profiles will be mediocre in terms of supporting severe
potential. Coupled with less than 5.5 C/km mid-level lapse rates,
updrafts are not expected to become overly robust, hence the
unlikelihood of a WW issuance. Nonetheless, one of the stronger 
line segments within the confluence band may support a couple strong
wind gusts this afternoon.

..Squitieri/Hart.. 09/22/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...AKQ...LWX...RAH...ILM...RNK...CHS...RLX...CAE...
GSP...MRX...

LAT...LON   34728287 37698066 38178016 38117943 37867891 37377855
            36847850 36217856 35427903 34447956 33578005 32978042
            32888089 33188152 34728287

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 22, 6:14 PM EDT	Mesoscale Discussion	SPC	Lancaster, Middlesex, Northumberland, Richmond, Westmoreland	2 hr
Sep 22, 1:08 PM EDT	Mesoscale Discussion	SPC	Brooke, Calhoun, Doddridge, Gilmer, Hancock, Harrison and 11 more	3 hr
Sep 22, 2:23 PM EDT	Tornado Watch	SPC	Brooke, Hancock, Marion, Marshall, Monongalia, Ohio and 1 more	6 hr
Sep 22, 4:08 PM EDT	Mesoscale Discussion	SPC	Brooke, Hancock, Monongalia, Ohio	97 min

Nearby

Mesoscale Discussions in North Carolina, 2021 Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in South Carolina, 2021 Every 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.