Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 2078

October 18, 201234 counties in North Carolina; 63 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Oct 18, 2012, 8:55 PM EDT for 34 counties in North Carolina; 63 counties in Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Oct 18, 2012, 8:55 PM EDT (00:55 UTC)
Expired
Oct 18, 2012, 11:00 PM EDT
In force
2 hr
Issued by
the Storm Prediction Center
Chance of a watch
40%
All 97 counties

Alamance County, NC, Cabarrus County, NC, Caswell County, NC, Chatham County, NC, Davidson County, NC, Davie County, NC, Durham County, NC, Edgecombe County, NC, Forsyth County, NC, Franklin County, NC, Gaston County, NC, Granville County, NC, Guilford County, NC, Halifax County, NC, Harnett County, NC, Iredell County, NC, Johnston County, NC, Lee County, NC, Mecklenburg County, NC, Montgomery County, NC, Moore County, NC, Nash County, NC, Northampton County, NC, Orange County, NC, Person County, NC, Randolph County, NC, Rockingham County, NC, Rowan County, NC, Stanly County, NC, Stokes County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Wilson County, NC, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Bedford County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charles City County, VA, Charlotte County, VA, Chesterfield County, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Petersburg, VA, City of Richmond, VA, City of Waynesboro, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fauquier County, VA, Fluvanna County, VA, Franklin County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Henry County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Loudoun County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mecklenburg County, VA, Nelson County, VA, New Kent County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Prince William County, VA, Rappahannock County, VA, Southampton County, VA, Spotsylvania County, VA, Stafford County, VA, Sussex County, VA, Warren County, VA

The radar

The Roanoke radar (KFCX), 115 km from the middle of the area, began a volume at 00:55 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

Roanoke, VA (KRNK), launched 00:00Z, 0.9 hours before the alert went out and 74 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-pSkew-T log-p diagram, Roanoke, VA at 00:00Z on 2012-10-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 322 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Roanoke, VA at 00:00Z on 2012-10-19The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 307 square meters per square second.1939587897117136Sfc1 km3 km6 km9 kmRMLM
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
322 J/kg
Mixed-layer CIN
-7 J/kg
Mixed-layer LCL
830 m above ground
0-6 km bulk shear
69 kt
0-1 km storm-relative helicity
307 m²/s²
0-3 km storm-relative helicity
353 m²/s²
Significant tornado parameter
0.6
Supercell composite
3.2

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.

IssuedProductOfficeCountiesLasted
Oct 19, 4:48 PM EDTMesoscale DiscussionSPCArlington, Fairfax, Fauquier, Loudoun, Prince William, City of Alexandria and 4 more87 min

Nearby

Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in North Carolina, 2012Every mesoscale discussion in 2012

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.