Alert archive / Virginia / Mesoscale Discussions in 2021

Mesoscale Discussion 845

June 3, 20215 states

The Storm Prediction Center issued this mesoscale discussion at Jun 3, 2021, 4:47 PM EDT for 5 states. It was in force for 88 min.

The area

The outline as issued.

The facts

Issued: Jun 3, 2021, 4:47 PM EDT (20:47 UTC)
Expired: Jun 3, 2021, 6:15 PM EDT
In force: 88 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 234

All 66 counties

Kent County, DE, New Castle 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, Frederick 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, Talbot County, MD, Gloucester County, NJ, Hunterdon County, NJ, Salem County, NJ, Somerset County, NJ, Berks County, PA, Bucks County, PA, Chester County, PA, Delaware County, PA, Lancaster County, PA, Lehigh County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA, York County, PA, Albemarle County, VA, Arlington County, VA, Buckingham County, VA, Caroline County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, Culpeper County, VA, Cumberland County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Hanover County, VA, King George County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Orange County, VA, Powhatan County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Westmoreland County, VA

The radar

The Sterling radar (KLWX), 39 km from the middle of the area, began a volume at 20:49 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, 8.8 hours before the alert went out and 31 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: 73 J/kg
Mixed-layer CIN: -52 J/kg
Mixed-layer LCL: 511 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 116 m²/s²
0-3 km storm-relative helicity: 118 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

990 
ACUS11 KWNS 032047
SWOMCD
SPC MCD 032047 
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-032215-

Mesoscale Discussion 0845
NWS Storm Prediction Center Norman OK
0347 PM CDT Thu Jun 03 2021

Areas affected...the Mid Atlantic region

Concerning...Severe Thunderstorm Watch 234...

Valid 032047Z - 032215Z

The severe weather threat for Severe Thunderstorm Watch 234
continues.

SUMMARY...Scattered strong/isolated severe storms continue from
southeastern Pennsylvania southwestward into central Virginia, where
locally damaging wind gusts remain the primary risk.

DISCUSSION...Latest radar loop shows a broken band of storms that
continues to evolve along and east of the higher terrain of
Pennsylvania/Maryland/Virginia.  Diurnal heating combined with the
relatively moist (generally mid to upper 60s dewpoints)
boundary-layer airmass across the area has pushed mixed-layer CAPE
values into the 1000 to 1500 J/kg range.  Coupled with
increasing/weakly veering flow with height which is aiding updraft
organization, isolated severe storms have evolved, a few exhibiting
supercell characteristics.  While marginally severe hail is
possible, greater risk is for locally damaging wind gusts --
particularly as storms grow upscale/congeal.  Meanwhile, an
isolated/brief tornado cannot be ruled out over the next 1-2 hours.

..Goss.. 06/03/2021

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

ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...

LAT...LON   37477908 39477769 40787530 40667449 38127599 37447826
            37477908

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 3, 1:46 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle	119 min
Jun 3, 2:48 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	6 hr

Nearby

Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in Maryland, 2021 Mesoscale Discussions in Pennsylvania, 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.