Alert archive / Virginia / Mesoscale Discussions in 2021

Mesoscale Discussion 1211

July 9, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Jul 9, 2021, 2:15 PM EDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 9, 2021, 2:15 PM EDT (18:15 UTC)
Expired: Jul 9, 2021, 4:15 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch possible
Chance of a watch: 40%

All 72 counties

Kent County, DE, New Castle County, DE, Sussex County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Harford County, MD, Howard County, MD, Kent 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, Granville County, NC, Northampton County, NC, Vance County, NC, Warren County, NC, Accomack County, VA, Amelia County, VA, Arlington County, VA, Brunswick County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Falls Church, VA, City of Franklin, VA, City of Fredericksburg, 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, Dinwiddie County, VA, Essex County, VA, Gloucester County, VA, Greensville County, VA, Hanover County, VA, Henrico County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Lunenburg County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Nottoway County, VA, Powhatan County, VA, Prince George County, VA, Richmond County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA

The radar

The Norfolk radar (KAKQ), 115 km from the middle of the area, began a volume at 18:15 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, 6.3 hours before the alert went out and 116 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 712 m above ground
0-6 km bulk shear: 12 kt
0-1 km storm-relative helicity: 57 m²/s²
0-3 km storm-relative helicity: 57 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

357 
ACUS11 KWNS 091815
SWOMCD
SPC MCD 091815 
NJZ000-MDZ000-DEZ000-VAZ000-PAZ000-NCZ000-DCZ000-092015-

Mesoscale Discussion 1211
NWS Storm Prediction Center Norman OK
0115 PM CDT Fri Jul 09 2021

Areas affected...eastern Virginia into eastern Maryland and Delaware

Concerning...Severe potential...Watch possible 

Valid 091815Z - 092015Z

Probability of Watch Issuance...40 percent

SUMMARY...Scattered storms are expected to form over the next few
hours with locally damaging wind gusts and small hail possible.

DISCUSSION...Surface convergence continues to increase in relation
to a developing low pressure trough, with westerly winds across
western VA and NC. GPS PWAT sensors indicate a relative maximum
around 1.80" over eastern VA, with continued heating further
destabilizing the air mass. Shear is weak, but the favorable time of
day and steepening low-level lapse rates should foster strong
outflow, with a few severe gusts possible. The increasing westerly
flow should push the better moisture eastward with time,

..Jewell/Bunting.. 07/09/2021

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

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

LAT...LON   36317743 36157819 36197893 36697877 37317812 37947768
            38967718 39607682 39737631 39767582 39707554 39357525
            38917526 38687533 38417548 37837570 37297592 36767654
            36317743

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 8, 10:01 PM EDT	Mesoscale Discussion	SPC	Sussex	59 min
Jul 9, 4:35 PM EDT	Mesoscale Discussion	SPC	New Castle	115 min
Jul 9, 5:40 PM EDT	Mesoscale Discussion	SPC	Beaufort, Bertie, Bladen, Brunswick, Chowan, Columbus and 14 more	95 min

Nearby

Mesoscale Discussions in Virginia, 2021 Mesoscale Discussions in Maryland, 2021 Mesoscale Discussions in North Carolina, 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.