Alert archive / Virginia / Mesoscale Discussions in 2011
Mesoscale Discussion 660
The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2011, 10:44 AM EDT for 5 states. It was in force for 61 min.
The area
The outline as issued.
The facts
- Issued
- Apr 28, 2011, 10:44 AM EDT (14:44 UTC)
- Expired
- Apr 28, 2011, 11:45 AM EDT
- In force
- 61 min
- Issued by
- the Storm Prediction Center
All 99 counties
Kent County, DE, New Castle 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, Talbot County, MD, Washington County, MD, Salem County, NJ, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington 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 Alexandria, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Danville, VA, City of Emporia, VA, City of Fairfax, VA, City of Falls Church, 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, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Henry County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mecklenburg County, VA, Middlesex County, VA, Nelson County, VA, New Kent County, VA, Northumberland 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, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Warren County, VA, Westmoreland County, VA, Berkeley County, WV, Jefferson County, WV
The radar
The Norfolk radar (KAKQ), 130 km from the middle of the area, began a volume at 14:47 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.
The nearest sounding before it
Roanoke, VA (KRNK), launched 12:00Z, 2.7 hours before the alert went out and 141 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 911 m above ground
- 0-6 km bulk shear
- 81 kt
- 0-1 km storm-relative helicity
- -166 m²/s²
- 0-3 km storm-relative helicity
- 43 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
The text
As transmitted, in the capitals the NWS used until 2016.
867 ACUS11 KWNS 281445 SWOMCD SPC MCD 281444 NJZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-NCZ000-281545- MESOSCALE DISCUSSION 0660 NWS STORM PREDICTION CENTER NORMAN OK 0944 AM CDT THU APR 28 2011 AREAS AFFECTED...THE DELMARVA INTO SRN VA CONCERNING...TORNADO WATCH 251... VALID 281444Z - 281545Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 251 CONTINUES. A NARROW AXIS OF MODERATE INSTABILITY CURRENTLY EXTENDS NWD ACROSS ERN VA TOWARD THE DELMARVA. THIS AIRMASS IS SUFFICIENTLY SHEARED FOR MAINTAINING THE ONGOING SEVERE BAND OF FRONTAL CONVECTION AS IT PROPAGATES TOWARD THE MIDDLE ATLANTIC COAST. LATEST RADAR DATA SUGGEST FASTER-MOVING LINE SEGMENTS AND BOW-TYPE STRUCTURES HAVE EVOLVED OVER CNTRL VA AND THIS ACTIVITY COULD PRODUCE VERY DAMAGING WINDS AS IT SPREADS TOWARD THE TIDEWATER REGION. ..DARROW.. 04/28/2011 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...PHI...AKQ...LWX...RNK... LAT...LON 36548015 39647791 39647491 36567726 36548015
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 27, 8:15 PM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 8 hr |
| Apr 28, 4:05 AM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 6 hr |
| Apr 28, 6:21 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 54 min |
| Apr 28, 9:45 AM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 6 hr |
| Apr 28, 11:49 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 56 min |
| Apr 28, 2:00 PM EDT | Mesoscale Discussion | SPC | Kent, Sussex | 60 min |
| Apr 28, 12:27 AM EDT | Mesoscale Discussion | SPC | Allegany, Frederick, Howard, Montgomery, Washington | 63 min |
| Apr 28, 12:41 AM EDT | Tornado Watch | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more | 7 hr |
| Apr 28, 7:38 AM EDT | Tornado Watch | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Charles, Dorchester and 10 more | 7 hr |
| Apr 28, 2:41 PM EDT | Tornado Watch | SPC | Dorchester, Somerset, Wicomico, Worcester | 6 hr |
| Apr 28, 6:33 PM EDT | Mesoscale Discussion | SPC | Dorchester, Saint Mary's, Somerset, Wicomico, Worcester | 57 min |
| Apr 28, 3:32 AM EDT | Mesoscale Discussion | SPC | Hunterdon, Sussex, Warren | 28 min |
| Apr 27, 9:22 PM EDT | Mesoscale Discussion | SPC | Buchanan, Dickenson, Lee, Russell, Scott, Smyth and 5 more | 53 min |
| Apr 27, 10:12 PM EDT | Mesoscale Discussion | SPC | Albemarle, Alleghany, Amelia, Amherst, Appomattox, Arlington and 68 more | 63 min |
| Apr 28, 12:34 AM EDT | Mesoscale Discussion | SPC | Buchanan, Dickenson, Lee, Russell, Scott, Tazewell and 3 more | 26 min |
Nearby
Mesoscale Discussions in Virginia, 2011Mesoscale Discussions in Maryland, 2011Mesoscale Discussions in Delaware, 2011Every mesoscale discussion in 2011
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.