Alert archive / Virginia / Mesoscale Discussions in 2021

Mesoscale Discussion 850

June 4, 20216 states

The Storm Prediction Center issued this mesoscale discussion at Jun 4, 2021, 4:12 PM EDT for 6 states. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued: Jun 4, 2021, 4:12 PM EDT (20:12 UTC)
Expired: Jun 4, 2021, 5:45 PM EDT
In force: 93 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 235...236

All 68 counties

Kent County, DE, New Castle County, DE, Sussex County, DE, Calvert County, MD, Caroline County, MD, Cecil County, MD, Dorchester County, MD, Harford County, MD, Kent County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Worcester County, MD, Atlantic County, NJ, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Ocean County, NJ, Salem County, NJ, Union County, NJ, Bronx County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Queens County, NY, Richmond County, NY, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA, Accomack County, VA, Charles City County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Hampton, VA, City of Hopewell, VA, City of Newport News, VA, City of Petersburg, VA, City of Poquoson, VA, City of Richmond, VA, City of Williamsburg, VA, Essex County, VA, Gloucester County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Prince George County, VA, Richmond County, VA, Surry County, VA, York County, VA

The radar

The Dover AFB radar (KDOX), 26 km from the middle of the area, began a volume at 20:14 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 8.2 hours before the alert went out and 109 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: 396 J/kg
Mixed-layer CIN: -12 J/kg
Mixed-layer LCL: 545 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 58 m²/s²
0-3 km storm-relative helicity: 44 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

604 
ACUS11 KWNS 042012
SWOMCD
SPC MCD 042012 
NYZ000-NJZ000-PAZ000-MDZ000-DEZ000-VAZ000-042145-

Mesoscale Discussion 0850
NWS Storm Prediction Center Norman OK
0312 PM CDT Fri Jun 04 2021

Areas affected...from eastern Virginia/the Chesapeake region
north-northeastward to the New York City area

Concerning...Severe Thunderstorm Watch 235...236...

Valid 042012Z - 042145Z

The severe weather threat for Severe Thunderstorm Watch 235, 236
continues.

SUMMARY...Isolated strong storms within bands of convection will
remain capable of producing gusty winds/minor damage.

DISCUSSION...Latest radar loop shows two rather distinct bands of
storms moving across the Mid Atlantic region.  One band -- within WW
235 crossing the Chesapeake Bay and adjacent eastern Virginia --
continues moving east-southeastward at around 30 kt, and will
continue affecting areas from the Delmarva Peninsula to the Richmond
area over the next hour or so.  Gusty winds, and local damage to
trees, will remain possible.

Farther north, a second band of storms is moving eastward at around
20 kt, and extends from the New York City area southwestward to the
lower Delaware Valley region.  Like the band farther to the south,
stronger cells within the line will be capable of gusty winds
locally, along with minor damage.

Storms in both areas will continue over the next couple of hours,
before beginning a gradual weakening trend this evening.

..Goss.. 06/04/2021

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

ATTN...WFO...OKX...PHI...AKQ...CTP...LWX...

LAT...LON   37387787 38167670 39177634 39637636 40117583 40537465
            41147397 40827335 39847402 38647496 37527543 36947600
            37027695 37387787

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 4, 2:26 PM EDT	Mesoscale Discussion	SPC	New Castle	94 min
Jun 4, 3:09 PM EDT	Severe Thunderstorm Watch	SPC	New Castle	5 hr
Jun 4, 12:46 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Calvert, Charles, Prince George's, Queen Anne's, Saint Mary's and 2 more	59 min
Jun 4, 12:59 PM EDT	Severe Thunderstorm Watch	SPC	Calvert, Charles, Dorchester, Saint Mary's, Somerset, Wicomico	7 hr

Nearby

Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in New Jersey, 2021 Mesoscale Discussions in Maryland, 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.