Alert archive / Virginia / Mesoscale Discussions in 2007

Mesoscale Discussion 1698

August 9, 20074 states

The Storm Prediction Center issued this mesoscale discussion at Aug 9, 2007, 2:41 PM EDT for 4 states. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued: Aug 9, 2007, 2:41 PM EDT (18:41 UTC)
Expired: Aug 9, 2007, 4:15 PM EDT
In force: 94 min
Issued by: the Storm Prediction Center

All 54 counties

Allegany County, MD, Anne Arundel County, MD, Calvert County, MD, Charles County, MD, Dorchester County, MD, Frederick County, MD, Garrett County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Washington County, MD, Wicomico County, MD, Bedford County, PA, Cambria County, PA, Fayette County, PA, Franklin County, PA, Fulton County, PA, Indiana County, PA, Somerset County, PA, Westmoreland County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, King George County, VA, Lancaster County, VA, Loudoun County, VA, Northumberland County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Shenandoah County, VA, Stafford County, VA, Warren County, VA, Westmoreland County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Preston County, WV

The radar

The Sterling radar (KLWX), 41 km from the middle of the area, began a volume at 18:43 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, 6.7 hours before the alert went out and 48 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: 547 J/kg
Mixed-layer CIN: -121 J/kg
Mixed-layer LCL: 1213 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 40 m²/s²
0-3 km storm-relative helicity: 117 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 3.4

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 9, 8:47 AM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Carroll, Cecil, Frederick, Harford and 6 more	58 min
Aug 9, 9:47 AM EDT	Severe Thunderstorm Watch	SPC	Allegany, Anne Arundel, Baltimore, Carroll, Frederick, Harford and 5 more	6 hr
Aug 9, 12:35 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Caroline, Cecil, Dorchester and 11 more	85 min
Aug 9, 12:48 PM EDT	Severe Thunderstorm Watch	SPC	Caroline, Cecil, Dorchester, Kent, Queen Anne's, Somerset and 3 more	3 hr
Aug 9, 1:22 PM EDT	Severe Thunderstorm Watch	SPC	Garrett	7 hr
Aug 9, 2:25 PM EDT	Mesoscale Discussion	SPC	Calvert, Charles, Dorchester, Saint Mary's, Somerset, Wicomico	2 hr
Aug 9, 7:23 PM EDT	Mesoscale Discussion	SPC	Allegany, Anne Arundel, Baltimore, Calvert, Caroline, Carroll and 16 more	67 min
Aug 9, 11:54 AM EDT	Mesoscale Discussion	SPC	Allegheny, Beaver, Butler, Fayette, Greene, Lawrence and 3 more	2 hr
Aug 9, 5:03 PM EDT	Mesoscale Discussion	SPC	Allegheny, Armstrong, Beaver, Butler, Fayette, Greene and 4 more	87 min

Nearby

Mesoscale Discussions in Virginia, 2007 Mesoscale Discussions in Maryland, 2007 Mesoscale Discussions in Pennsylvania, 2007 Every mesoscale discussion in 2007

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.