Alert archive / Virginia / Mesoscale Discussions in 2011
Mesoscale Discussion 459
The Storm Prediction Center issued this mesoscale discussion at Apr 16, 2011, 4:29 PM EDT for 4 states. It was in force for 31 min.
The area
The outline as issued.
The facts
- Issued
- Apr 16, 2011, 4:29 PM EDT (20:29 UTC)
- Expired
- Apr 16, 2011, 5:00 PM EDT
- In force
- 31 min
- Issued by
- the Storm Prediction Center
All 58 counties
Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Calvert 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, Adams County, PA, Chester County, PA, Franklin County, PA, Fulton County, PA, Lancaster County, PA, York County, PA, Arlington County, VA, City of Alexandria, 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, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Pendleton County, WV
The radar
The Sterling radar (KLWX), 25 km from the middle of the area, began a volume at 20:33 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 8.5 hours before the alert went out and 27 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
- 533 m above ground
- 0-6 km bulk shear
- 56 kt
- 0-1 km storm-relative helicity
- 473 m²/s²
- 0-3 km storm-relative helicity
- 699 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
843
ACUS11 KWNS 162030
SWOMCD
SPC MCD 162029
PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-162100-
MESOSCALE DISCUSSION 0459
NWS STORM PREDICTION CENTER NORMAN OK
0329 PM CDT SAT APR 16 2011
AREAS AFFECTED...NRN VA / MUCH OF MD / E WV PANHANDLE / FAR SRN PA
CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 151...
VALID 162029Z - 162100Z
ISOLD TORNADO THREAT CONTINUES ACROSS MUCH OF NRN VA/MD AND THE ERN
WV PANHANDLE. A TORNADO RISK MAY ALSO EXTEND NWD INTO FAR SRN
PA...LIKELY REQUIRING A WW WITHIN THE HOUR.
THE AIRMASS IS CONTINUING TO DESTABILIZE ACROSS THE MID-ATLANTIC AND
PORTIONS OF THE HIGHER TERRAIN OF THE CNTRL APPALACHIANS. SINGLE
SITE RADAR IMAGERY SHOWS ROTATING STORMS OVER THE SWRN HALF OF THE
DISCUSSION AREA AND GIVEN THE DEGREE OF FORCING AND PROBABLE AIRMASS
RECOVERY ALONG THE MASON-DIXON LINE...WILL LIKELY NECESSITATE A NEW
WW TO THE N OF THE EXISTING TORNADO WATCH. VERY STRONG WIND PROFILE
IN PLACE ACROSS THE REGION /REFERENCE KLWX VAD DATA---50 KTS 0-1 KM
SHEAR/ WILL SUPPORT THE POTENTIAL FOR ISOLD TORNADO/S INTO THE EARLY
EVENING HOURS.
..SMITH.. 04/16/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PHI...AKQ...CTP...LWX...
LAT...LON 38287958 39727887 39937825 40087724 40187643 40127576
39917565 39507586 37987600 38217742 38167838 38287958SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 16, 12:52 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Calvert, Caroline, Charles, Dorchester, Frederick and 10 more | 113 min |
| Apr 16, 1:29 PM EDT | Tornado Watch | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more | 8 hr |
| Apr 16, 4:41 PM EDT | Tornado Watch | SPC | Caroline, Cecil, Kent, Queen Anne's, Talbot | 6 hr |
| Apr 16, 6:38 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Caroline, Carroll, Cecil and 13 more | 97 min |
| Apr 16, 10:43 AM EDT | Mesoscale Discussion | SPC | Fayette, Greene, Washington | 62 min |
| Apr 16, 1:34 PM EDT | Mesoscale Discussion | SPC | Beaver, Crawford, Lawrence, Mercer, Washington | 116 min |
| Apr 16, 2:05 PM EDT | Mesoscale Discussion | SPC | Adams, Bedford, Cumberland, Dauphin, Franklin, Fulton and 6 more | 55 min |
| Apr 16, 10:39 AM EDT | Mesoscale Discussion | SPC | Brunswick, Charles City, Chesterfield, Dinwiddie, Gloucester, Greensville and 25 more | 2 hr |
| Apr 16, 12:02 PM EDT | Tornado Watch | SPC | Amelia, Amherst, Appomattox, Bedford, Brunswick, Buckingham and 62 more | 11 hr |
| Apr 16, 2:28 PM EDT | Mesoscale Discussion | SPC | Amelia, Brunswick, Charles City, Charlotte, Chesterfield, Cumberland and 43 more | 92 min |
| Apr 16, 4:49 PM EDT | Mesoscale Discussion | SPC | Brunswick, Caroline, Charles City, Chesterfield, Dinwiddie, Essex and 33 more | 86 min |
| Apr 16, 6:59 PM EDT | Mesoscale Discussion | SPC | Greensville, Isle of Wight, Prince George, Southampton, Surry, Sussex and 9 more | 91 min |
Nearby
Mesoscale Discussions in Virginia, 2011Mesoscale Discussions in Maryland, 2011Mesoscale Discussions in West Virginia, 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.