Alert archive / Virginia / Mesoscale Discussions in 2017
Mesoscale Discussion 923
The Storm Prediction Center issued this mesoscale discussion at May 30, 2017, 5:56 PM EDT for 24 counties in Virginia; Jefferson County, West Virginia. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- May 30, 2017, 5:56 PM EDT (21:56 UTC)
- Expired
- May 30, 2017, 7:00 PM EDT
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 40%
All 25 counties
Caroline County, VA, City of Fredericksburg, VA, City of Richmond, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Essex County, VA, Fauquier County, VA, Frederick County, VA, Hanover County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, New Kent County, VA, Orange County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Jefferson County, WV
The radar
The Sterling radar (KLWX), 58 km from the middle of the area, began a volume at 21:58 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 9.9 hours before the alert went out and 56 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
- 70 J/kg
- Mixed-layer CIN
- -49 J/kg
- Mixed-layer LCL
- 528 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 125 m²/s²
- 0-3 km storm-relative helicity
- 167 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.5
The text
As transmitted.
201
ACUS11 KWNS 302157
SWOMCD
SPC MCD 302156
VAZ000-MDZ000-WVZ000-302300-
Mesoscale Discussion 0923
NWS Storm Prediction Center Norman OK
0456 PM CDT Tue May 30 2017
Areas affected...Northern VA
Concerning...Severe potential...Watch possible
Valid 302156Z - 302300Z
Probability of Watch Issuance...40 percent
SUMMARY...Isolated severe thunderstorms will continue across
northern Virginia into the early evening hours. Large hail will be
the primary threat, though locally damaging winds are possible.
DISCUSSION...Strong boundary-layer heating has contributed to steep
low-level lapse rates west of the wedge front across VA. As a
result, surface-based thunderstorms have developed along the eastern
fringe of this more buoyant air mass and are slowly maturing within
a corridor of favorable low-level convergence. High-res model
guidance has been consistent regarding this development and
supercells are evolving within a strongly sheared and favorably
unstable environment. Latest radar data strongly suggests at least
golf ball sized hail with the supercell over Culpeper/Stafford
Counties. There is increasing concern that this activity will
linger into the evening hours as they propagate southeast along the
wedge front. Hail and wind can be expected with this activity.
..Darrow/Guyer.. 05/30/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...LWX...
LAT...LON 39397773 38747750 38317716 37907668 37447675 37457746
38207825 39277839 39397773SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 30, 12:03 PM EDT | Mesoscale Discussion | SPC | Hampshire, Mineral | 2 hr |
Nearby
Mesoscale Discussions in Virginia, 2017Mesoscale Discussions in West Virginia, 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; radar from the NEXRAD Level II archive.