Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 526
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 1:04 PM EDT for 4 states. It was in force for 56 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 1:04 PM EDT (17:04 UTC)
- Expired
- May 4, 2021, 2:00 PM EDT
- In force
- 56 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...severe thunderstorm watch likely
- Chance of a watch
- 80%
All 115 counties
Charles County, MD, Caswell County, NC, Northampton County, NC, Person County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Vance County, NC, Warren County, NC, Albemarle County, VA, Alleghany County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Augusta County, VA, Bath County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Carroll County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Covington, VA, City of Danville, VA, City of Emporia, VA, City of Fairfax, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Galax, VA, City of Harrisonburg, VA, City of Hopewell, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Petersburg, VA, City of Radford, VA, City of Richmond, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, City of Williamsburg, VA, Craig County, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Giles County, VA, Goochland County, VA, Grayson County, VA, Greene County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Henry County, VA, Highland County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mecklenburg County, VA, Montgomery County, VA, Nelson County, VA, New Kent County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Prince William County, VA, Pulaski County, VA, Rappahannock County, VA, Richmond County, VA, Roanoke County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Southampton County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Warren County, VA, Westmoreland County, VA, Wythe County, VA, Greenbrier County, WV, Hardy County, WV, Mercer County, WV, Monroe County, WV, Pendleton County, WV, Pocahontas County, WV, Randolph County, WV, Summers County, WV
The radar
The Roanoke radar (KFCX), 122 km from the middle of the area, began a volume at 17:07 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
Roanoke, VA (KRNK), launched 12:00Z, 5.1 hours before the alert went out and 53 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
- 649 J/kg
- Mixed-layer CIN
- -120 J/kg
- Mixed-layer LCL
- 750 m above ground
- 0-6 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 116 m²/s²
- 0-3 km storm-relative helicity
- 105 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted.
284
ACUS11 KWNS 041704
SWOMCD
SPC MCD 041704
VAZ000-MDZ000-NCZ000-WVZ000-041800-
Mesoscale Discussion 0526
NWS Storm Prediction Center Norman OK
1204 PM CDT Tue May 04 2021
Areas affected...Eastern West Virginia...northern North
Carolina...and Virginia
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 041704Z - 041800Z
Probability of Watch Issuance...80 percent
SUMMARY...A broken line of thunderstorms is expected to develop in
the coming hours across eastern West Virginia and western Virginia.
These storms will pose a risk for damaging winds as they move east.
A watch is likely in the next 1-2 hours.
DISCUSSION...Satellite and radar trends have shown a recent uptick
in convection across eastern West Virginia and far western Virginia
over the past 30-60 minutes. This activity is primarily being driven
by lift ahead of a shortwave impulse - likely a lingering MCV from
prior convection across the mid-South. Morning soundings from NC and
VA show steep mid-level lapse rates near 8 C/km and mostly clear
skies have allowed temperatures to warm into the low to mid 80s.
These factors, combined with rich boundary-layer moisture (dewpoints
in the 60s), are supporting increasing MLCAPE values with 1000 J/kg
noted across central VA in recent RAP mesoanalysis. Continued
boundary-layer heating will further augment instability while
reducing MLCIN through the mid afternoon. Increasing upper-level
flow in the vicinity of the shortwave should support effective bulk
shear values near 30-35 knots, which will support at least some
storm organization within a broken line. Given steepening low-level
lapse rates across the region, the primary threat appears to be
damaging winds, though a few instances of severe hail are possible.
..Moore/Grams.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...RAH...RNK...PBZ...RLX...
LAT...LON 36758151 37438114 38628019 39107935 39087779 38757696
38037659 37247654 36597687 36317751 36308031 36418099
36758151SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 1:51 PM EDT | Severe Thunderstorm Watch | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 8 more | 6 hr |
| May 4, 3:50 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Charles, Dorchester, Howard and 7 more | 115 min |
| May 4, 9:37 AM EDT | Severe Thunderstorm Watch | SPC | Cherokee, Clay, Graham, Macon, Swain | 3 hr |
| May 4, 1:21 PM EDT | Mesoscale Discussion | SPC | Clay, Macon | 114 min |
| May 4, 4:16 PM EDT | Mesoscale Discussion | SPC | Alamance, Anson, Bladen, Cabarrus, Caswell, Chatham and 35 more | 119 min |
| May 4, 4:56 PM EDT | Severe Thunderstorm Watch | SPC | Anson, Bladen, Cumberland, Harnett, Hoke, Lee and 7 more | 3 hr |
| May 4, 5:52 PM EDT | Mesoscale Discussion | SPC | Charles City, Gloucester, Greensville, Isle of Wight, James City, Prince George and 18 more | 53 min |
Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in North Carolina, 2021Mesoscale Discussions in West 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.