Alert archive / Virginia / Mesoscale Discussions in 2020

Mesoscale Discussion 968

June 22, 20205 states

The Storm Prediction Center issued this mesoscale discussion at Jun 22, 2020, 1:58 PM EDT for 5 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jun 22, 2020, 1:58 PM EDT (17:58 UTC)
Expired: Jun 22, 2020, 4:30 PM EDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 127 counties

Allegany County, MD, Baltimore County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Garrett County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Allegany County, NY, Cattaraugus County, NY, Chautauqua County, NY, Adams County, PA, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Bedford County, PA, Blair County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Crawford County, PA, Cumberland County, PA, Dauphin County, PA, Elk County, PA, Erie County, PA, Fayette County, PA, Forest County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lawrence County, PA, Lycoming County, PA, McKean County, PA, Mercer County, PA, Mifflin County, PA, Perry County, PA, Potter County, PA, Snyder County, PA, Somerset County, PA, Tioga County, PA, Union County, PA, Venango County, PA, Warren County, PA, Washington County, PA, Westmoreland County, PA, York County, PA, Albemarle County, VA, Amelia County, VA, Arlington County, VA, Augusta County, VA, Buckingham County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Hopewell, VA, City of Manassas, VA, City of Manassas Park, VA, City of Petersburg, VA, City of Richmond, VA, City of Staunton, VA, City of Waynesboro, VA, City of Williamsburg, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Frederick County, VA, Goochland County, VA, Greene County, VA, Hanover County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Nelson County, VA, New Kent County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Powhatan County, VA, Prince George County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Monongalia County, WV, Morgan County, WV, Pendleton County, WV, Preston County, WV, Tucker County, WV

The radar

The State College radar (KCCX), 100 km from the middle of the area, began a volume at 18:01 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.0 hours before the alert went out and 138 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: 333 J/kg
Mixed-layer CIN: -93 J/kg
Mixed-layer LCL: 968 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 48 m²/s²
0-3 km storm-relative helicity: 69 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

343 
ACUS11 KWNS 221759
SWOMCD
SPC MCD 221758 
PAZ000-VAZ000-MDZ000-DCZ000-NYZ000-WVZ000-OHZ000-222030-

Mesoscale Discussion 0968
NWS Storm Prediction Center Norman OK
1258 PM CDT Mon Jun 22 2020

Areas affected...portions of the Mid-Atlantic...eastern Great
Lakes...Upper Ohio Valley

Concerning...Severe potential...Watch unlikely 

Valid 221758Z - 222030Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated to scattered strong to severe storms are expected
across portions of the Mid-Atlantic this afternoon. Damaging wind
gusts and marginally severe hail are the main severe threats. A
watch issuance is unlikely at this time, but convective trends will
be monitored closely.

DISCUSSION...An upper-level shortwave trough is moving northeast
across the Appalachians and eastern Great Lakes and into the
Mid-Atlantic today. At the surface, a remnant MCV continues to
slowly move northeast and is currently analyzed in northeast Ohio.
Storms have developed along the leading edge of the forcing for
ascent across the eastern Great Lakes and Mid-Atlantic/vicinity with
a surface pressure trough helping to focus low-level convergence and
convective initiation in western/central Pennsylvania into West
Virginia and Virginia. 

Daytime heating of a moist airmass (surface dewpoints in the upper
60s to low 70s F) has resulted in a maturing Cu field across the
Mid-Atlantic with some locations beginning to breach their
respective convective temperatures. MLCAPE of 1000-2500 J/kg across
the region will support deep convection with damaging wind gusts
possible given steep low-level lapse rates and water loaded
downdrafts. The lack of flow aloft will limit storm organization and
mostly outflow dominant multicellular convection is likely. However,
forcing for ascent from the upper-level shortwave trough coupled
with surface features like the MCV and surface pressure trough may
act to focus/maintain storms in a more organized manner and lead to
a localized increase of severe hail/wind potential.

..Nauslar/Guyer.. 06/22/2020

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

ATTN...WFO...BGM...AKQ...BUF...CTP...LWX...RNK...PBZ...RLX...
CLE...

LAT...LON   37277657 36907798 37797914 39297994 40708058 41818089
            42367958 42587851 42497776 42027704 41337687 40077665
            38627656 37277657

Nearby

Mesoscale Discussions in Virginia, 2020 Mesoscale Discussions in Pennsylvania, 2020 Mesoscale Discussions in Maryland, 2020 Every mesoscale discussion in 2020

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.