Alert archive / Virginia / Mesoscale Discussions in 2017
Mesoscale Discussion 461
The Storm Prediction Center issued this mesoscale discussion at Apr 6, 2017, 12:18 PM EDT for 5 states. It was in force for 57 min.
The area
The outline as issued.
The facts
- Issued
- Apr 6, 2017, 12:18 PM EDT (16:18 UTC)
- Expired
- Apr 6, 2017, 1:15 PM EDT
- In force
- 57 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 63 counties
Kent County, DE, New Castle County, DE, Sussex County, DE, Anne Arundel County, MD, Calvert County, MD, Caroline County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Harford 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, Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Ocean County, NJ, Salem County, NJ, Chester County, PA, Delaware County, PA, Philadelphia County, PA, Arlington County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Colonial Heights, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Hopewell, VA, City of Manassas, VA, City of Manassas Park, VA, City of Richmond, VA, Essex County, VA, Fairfax County, VA, Gloucester County, VA, Goochland County, VA, Hanover County, VA, Henrico County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Louisa County, VA, Middlesex County, VA, New Kent County, VA, Northumberland County, VA, Orange County, VA, Powhatan County, VA, Prince William County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Westmoreland County, VA
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, 4.3 hours before the alert went out and 114 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
- 550 m above ground
- 0-6 km bulk shear
- 75 kt
- 0-1 km storm-relative helicity
- 243 m²/s²
- 0-3 km storm-relative helicity
- 459 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
503
ACUS11 KWNS 061619
SWOMCD
SPC MCD 061618
NJZ000-PAZ000-MDZ000-DEZ000-VAZ000-DCZ000-061715-
Mesoscale Discussion 0461
NWS Storm Prediction Center Norman OK
1118 AM CDT Thu Apr 06 2017
Areas affected...Portions of the Mid-Atlantic
Concerning...Severe potential...Watch possible
Valid 061618Z - 061715Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated instances of damaging winds may occur through mid
afternoon from Virginia northward to southern New Jersey. Watch
issuance may be possible if convective trends warrant.
DISCUSSION...Several small bowing segments have organized over
northern/eastern Virginia late this morning/early this afternoon, on
the nose of robust DCVA associated with a sharp impulse currently
lifting north into Virginia. In response, a surface cyclone appears
to be organizing over far northern Virginia, with a sharpening
trough extending to its south/southeast. Enhanced surface
convergence (along this trough, as well as the front to its west)
and larger-scale ascent over the region will likely maintain pockets
of strong convection lifting northeast from Virginia towards
southeastern Pennsylvania and southern New Jersey this afternoon.
The near-surface thermal profile becomes considerably more stable
with northeastward extent, but considering the strength of forcing
for ascent, an isolated damaging-wind risk may extend into southern
New Jersey through the afternoon hours, especially where weak
diurnal heating occurs. However, due to the expected disorganized
nature of the threat, watch issuance is not currently anticipated.
Surface/radar observations will be monitored for a more organized
uptick in the damaging wind threat, though.
..Picca/Hart.. 04/06/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...AKQ...CTP...LWX...
LAT...LON 38857503 37417639 37227751 37427814 38147823 39027717
39347671 40117567 40147467 39927409 39297451 38857503SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 6, 12:45 PM EDT | Severe Thunderstorm Watch | SPC | Kent, New Castle, Sussex | 4 hr |
| Apr 6, 3:12 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 63 min |
| Apr 6, 5:59 AM EDT | Mesoscale Discussion | SPC | Calvert, Charles, Dorchester, Saint Mary's | 91 min |
| Apr 6, 7:06 AM EDT | Tornado Watch | SPC | Dorchester, Somerset, Wicomico, Worcester | 8 hr |
| Apr 6, 12:51 AM EDT | Mesoscale Discussion | SPC | Appomattox, Bedford, Campbell, Charlotte, Floyd, Franklin and 8 more | 114 min |
| Apr 6, 10:38 AM EDT | Mesoscale Discussion | SPC | Amelia, Brunswick, Caroline, Charles City, Chesterfield, Dinwiddie and 37 more | 67 min |
Nearby
Mesoscale Discussions in Virginia, 2017Mesoscale Discussions in Maryland, 2017Mesoscale Discussions in New Jersey, 2017Every mesoscale discussion in 2017
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.