Alert archive / Virginia / Mesoscale Discussions in 2011
Mesoscale Discussion 665
The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2011, 2:00 PM EDT for Kent County, Sussex County, Delaware; 13 counties in Maryland; 53 counties in Virginia. It was in force for 60 min.
The area
The outline as issued.
The facts
- Issued
- Apr 28, 2011, 2:00 PM EDT (18:00 UTC)
- Expired
- Apr 28, 2011, 3:00 PM EDT
- In force
- 60 min
- Issued by
- the Storm Prediction Center
All 68 counties
Kent County, DE, Sussex County, DE, Anne Arundel County, MD, Calvert County, MD, Caroline County, MD, Charles County, MD, Dorchester 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, Worcester County, MD, 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 Chesapeake, 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 Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Richmond, VA, City of Suffolk, VA, City of Virginia Beach, 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, 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, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA
The radar
The Norfolk radar (KAKQ), 93 km from the middle of the area, began a volume at 18:00 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
Wallops Is Stn, VA (KWAL), launched 12:00Z, 6.0 hours before the alert went out and 121 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
- 90 J/kg
- Mixed-layer CIN
- -342 J/kg
- Mixed-layer LCL
- 795 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 295 m²/s²
- 0-3 km storm-relative helicity
- 277 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted, in the capitals the NWS used until 2016.
523 ACUS11 KWNS 281800 SWOMCD SPC MCD 281800 DEZ000-MDZ000-VAZ000-NCZ000-DCZ000-281900- MESOSCALE DISCUSSION 0665 NWS STORM PREDICTION CENTER NORMAN OK 0100 PM CDT THU APR 28 2011 AREAS AFFECTED...DELMARVA INTO SRN VA CONCERNING...TORNADO WATCH 251... VALID 281800Z - 281900Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 251 CONTINUES. TORNADO WATCH 251 IS SCHEDULED TO EXPIRE AT 19Z BUT LOW LEVEL WINDS HAVE YET TO VEER SIGNIFICANTLY. THIS HAS ALLOWED AN AXIS OF MODEST INSTABILITY TO LINGER ACROSS THE TIDEWATER REGION AHEAD OF THE MAIN COLD FRONT. THERE IS SOME CONCERN THAT NEW DEVELOPMENT MAY OCCUR ALONG WRN FRINGE OF MOIST/INSTABILITY PLUME WHICH WOULD NECESSITATE AN EXTENSION OF THE ONGOING SEVERE THREAT. A NEW WW MAY BE REQUIRED TO ACCOUNT FOR THIS SCENARIO. ..DARROW.. 04/28/2011 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...PHI...AKQ...LWX... LAT...LON 36637840 39127711 39527580 38367497 36557593 36637840
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, 10:44 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 61 min |
| Apr 28, 11:49 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 56 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 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.