Alert archive / Virginia / Mesoscale Discussions in 2016

Mesoscale Discussion 1417

July 28, 20166 states

The Storm Prediction Center issued this mesoscale discussion at Jul 28, 2016, 12:58 PM EDT for 6 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 28, 2016, 12:58 PM EDT (16:58 UTC)
Expired: Jul 28, 2016, 3:00 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 80%

All 76 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, 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, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Atlantic County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Adams County, PA, Chester County, PA, Delaware County, PA, Philadelphia County, PA, York County, PA, Albemarle County, VA, Arlington 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 Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Culpeper 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, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Northumberland County, VA, Orange County, VA, Page 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, Jefferson County, WV

The radar

The Sterling radar (KLWX), 55 km from the middle of the area, began a volume at 16:58 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.

Severe Thunderstorm Watch 418Jul 28, 1:25 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 5.0 hours before the alert went out and 47 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: 552 J/kg
Mixed-layer CIN: -98 J/kg
Mixed-layer LCL: 1083 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 13 m²/s²
0-3 km storm-relative helicity: 87 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.8

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 28, 1:27 PM EDT	Severe Thunderstorm Watch	SPC	Kent, New Castle, Sussex	11 hr
Jul 28, 4:10 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	95 min
Jul 28, 6:52 PM EDT	Mesoscale Discussion	SPC	Kent, New Castle, Sussex	83 min
Jul 28, 1:28 PM EDT	Mesoscale Discussion	SPC	Alleghany, Bedford, Bland, Botetourt, Craig, Floyd and 12 more	3 hr
Jul 28, 2:08 PM EDT	Severe Thunderstorm Watch	SPC	Alleghany, Amherst, Appomattox, Bath, Bedford, Bland and 29 more	10 hr
Jul 28, 2:57 PM EDT	Mesoscale Discussion	SPC	Accomack, Amelia, Brunswick, Charles City, Chesterfield, Dinwiddie and 36 more	3 hr

Nearby

Mesoscale Discussions in Virginia, 2016 Mesoscale Discussions in Maryland, 2016 Mesoscale Discussions in New Jersey, 2016 Every mesoscale discussion in 2016

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.