Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 973
The Storm Prediction Center issued this mesoscale discussion at Jun 14, 2021, 6:41 PM EDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 14, 2021, 6:41 PM EDT (22:41 UTC)
- Expired
- Jun 14, 2021, 8:45 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 52 counties
Kent County, DE, New Castle County, DE, Sussex County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Arlington County, VA, Caroline County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, Culpeper County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Greene County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Rockingham County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA
The radar
The Sterling radar (KLWX), 50 km from the middle of the area, began a volume at 22:43 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 10.7 hours before the alert went out and 42 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
- 2 J/kg
- Mixed-layer CIN
- -447 J/kg
- Mixed-layer LCL
- 1007 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 31 m²/s²
- 0-3 km storm-relative helicity
- 87 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
485
ACUS11 KWNS 142241
SWOMCD
SPC MCD 142241
NJZ000-MDZ000-DEZ000-PAZ000-VAZ000-DCZ000-WVZ000-150045-
Mesoscale Discussion 0973
NWS Storm Prediction Center Norman OK
0541 PM CDT Mon Jun 14 2021
Areas affected...Northern Virginia into Maryland and Delaware
Concerning...Severe potential...Watch likely
Valid 142241Z - 150045Z
Probability of Watch Issuance...80 percent
SUMMARY...The environment ahead of an approaching cold front is
supportive for strong to severe thunderstorms across northern
Virginia, eastern Maryland, and Delaware. Storms along, and possibly
ahead of the front will pose a risk for severe hail and damaging
wind into the evening hours.
DISCUSSION...Strong convection continues to develop along a cold
front across southern PA into northern WV, resulting in a few wind
damage reports as they move to the east. Ahead of this front across
northern VA and MD, temperatures in the 80s and low 90s with
dewpoints in the 60s are supporting 1000-1500 J/kg MLCAPE with
minimal inhibition per RAP mesoanalysis estimates. Additionally,
strong upper-level flow over the region is supporting 40-50 knots of
effective bulk shear, which will help organize any convection that
develops in this thermodynamic environment.
Thunderstorms will likely move into the northern VA region by 00 UTC
along the front, but convective development ahead of the front
within a subtle lee trough (where a growing field of cumulus is
noted in recent GOES imagery) is possible in the coming hours. Shear
vectors oriented nearly along the front should support semi-discrete
to linear clusters that will pose a hail and damaging wind risk.
While there is some uncertainty regarding the exact timing of storm
arrival and the potential for increasing MLCIN after 01 UTC with the
onset of diurnal cooling, the environment should generally remain
supportive of a severe risk into the evening hours. A watch will
likely be needed to cover this threat.
..Moore/Guyer.. 06/14/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...CTP...LWX...
LAT...LON 38557889 39097795 39457739 39747686 39967608 39817514
39127509 38317535 37977597 37887654 37957706 38027767
38207894 38557889SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 14, 2:06 PM EDT | Severe Thunderstorm Watch | SPC | New Castle | 9 hr |
| Jun 14, 6:18 PM EDT | Mesoscale Discussion | SPC | New Castle | 117 min |
| Jun 14, 7:29 PM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 6 hr |
| Jun 14, 11:31 AM EDT | Mesoscale Discussion | SPC | Allegany, Garrett | 89 min |
| Jun 14, 3:55 PM EDT | Mesoscale Discussion | SPC | Allegany, Garrett, Washington | 65 min |
| Jun 14, 3:59 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Garrett, Washington | 6 hr |
| Jun 14, 7:37 PM EDT | Mesoscale Discussion | SPC | Allegany, Garrett | 113 min |
| Jun 14, 1:40 PM EDT | Mesoscale Discussion | SPC | Burlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 3 more | 3 hr |
Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in Maryland, 2021Mesoscale Discussions in Delaware, 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.