Alert archive / North Carolina / Mesoscale Discussions in 2021
Mesoscale Discussion 1305
The Storm Prediction Center issued this mesoscale discussion at Jul 17, 2021, 1:15 PM EDT for 26 counties in North Carolina; 24 counties in Virginia. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 17, 2021, 1:15 PM EDT (17:15 UTC)
- Expired
- Jul 17, 2021, 3:45 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 50 counties
Alamance County, NC, Alexander County, NC, Caswell County, NC, Chatham County, NC, Davidson County, NC, Davie County, NC, Durham County, NC, Forsyth County, NC, Franklin County, NC, Granville County, NC, Guilford County, NC, Iredell County, NC, Lee County, NC, Nash County, NC, Orange County, NC, Person County, NC, Randolph County, NC, Rockingham County, NC, Rowan County, NC, Stokes County, NC, Surry County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wilkes County, NC, Yadkin County, NC, Amelia County, VA, Appomattox County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Charlotte County, VA, Chesterfield County, VA, City of Danville, VA, City of Emporia, VA, City of Martinsville, VA, Cumberland County, VA, Dinwiddie County, VA, Franklin County, VA, Goochland County, VA, Greensville County, VA, Halifax County, VA, Henry County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nottoway County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA
The radar
The Roanoke radar (KFCX), 101 km from the middle of the area, began a volume at 17:17 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, 5.3 hours before the alert went out and 62 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
- 966 J/kg
- Mixed-layer CIN
- -78 J/kg
- Mixed-layer LCL
- 843 m above ground
- 0-6 km bulk shear
- 13 kt
- 0-1 km storm-relative helicity
- 12 m²/s²
- 0-3 km storm-relative helicity
- 19 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
515
ACUS11 KWNS 171716
SWOMCD
SPC MCD 171715
VAZ000-NCZ000-171945-
Mesoscale Discussion 1305
NWS Storm Prediction Center Norman OK
1215 PM CDT Sat Jul 17 2021
Areas affected...Portions of southern VA and western/central NC
Concerning...Severe potential...Watch unlikely
Valid 171715Z - 171945Z
Probability of Watch Issuance...20 percent
SUMMARY...A threat for occasional damaging wind gusts should
continue as storms move eastward this afternoon. The overall severe
threat will probably remain fairly isolated/marginal, and watch
issuance appears unlikely at this time.
DISCUSSION...Storms have recently formed along/east of the Blue
Ridge Mountains in southern VA and western NC. Additional storms may
develop this afternoon along a pre-frontal trough across
south-central VA into central NC. Visible satellite imagery shows
mostly clear skies ahead of this activity, and robust diurnal
heating has already warmed surface temperatures into the upper 80s
and lower 90s as of 17Z. MLCAPE of 1500-3000 J/kg will be present
across the warm sector, even with mid-level lapse rates remaining
poor. Steepening low-level lapse rates should support some potential
for strong/gusty downdraft winds with any loosely organized clusters
that can form. However, deep-layer shear is expected to remain quite
weak across this region (25 kt or less), with the stronger mid-level
southwesterly flow displaced well to the north. This should keep
overall storm organization modest at best, and the threat for
damaging wind gusts fairly isolated. At this point, it appears that
Severe Thunderstorm Watch issuance will probably not be needed due
to the limited storm organization expected.
..Gleason/Dial.. 07/17/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...RAH...RNK...GSP...
LAT...LON 35528102 35938140 36438120 37058005 37487884 37777832
37737756 37027740 36167768 35497850 35367964 35528102SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 17, 12:00 PM EDT | Mesoscale Discussion | SPC | Arlington, Clarke, Fairfax, Fauquier, Frederick, Loudoun and 8 more | 3 hr |
| Jul 17, 1:13 PM EDT | Severe Thunderstorm Watch | SPC | Albemarle, Arlington, Augusta, Clarke, Culpeper, Fairfax and 28 more | 10 hr |
| Jul 17, 3:02 PM EDT | Mesoscale Discussion | SPC | Arlington, Fairfax, Prince William, Stafford, City of Alexandria, City of Fairfax and 4 more | 88 min |
| Jul 17, 4:38 PM EDT | Mesoscale Discussion | SPC | Arlington, Clarke, Culpeper, Fairfax, Fauquier, Frederick and 19 more | 97 min |
| Jul 17, 6:54 PM EDT | Mesoscale Discussion | SPC | Arlington, Clarke, Culpeper, Fairfax, Fauquier, Frederick and 21 more | 2 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.