Alert archive / Virginia / Mesoscale Discussions in 2018
Mesoscale Discussion 1469
The Storm Prediction Center issued this mesoscale discussion at Sep 17, 2018, 3:25 PM EDT for Calvert County, Charles County, Saint Mary's County, Maryland; 22 counties in Virginia. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 17, 2018, 3:25 PM EDT (19:25 UTC)
- Expired
- Sep 17, 2018, 5:30 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
All 25 counties
Calvert County, MD, Charles County, MD, Saint Mary's County, MD, Amelia County, VA, Brunswick County, VA, Caroline County, VA, Chesterfield County, VA, City of Colonial Heights, VA, City of Hopewell, VA, City of Petersburg, VA, City of Richmond, VA, Dinwiddie County, VA, Essex County, VA, Goochland County, VA, Hanover County, VA, Henrico County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nottoway County, VA, Powhatan County, VA, Richmond County, VA, Westmoreland County, VA
The radar
The Norfolk radar (KAKQ), 79 km from the middle of the area, began a volume at 19:25 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, 7.4 hours before the alert went out and 162 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
- 117 J/kg
- Mixed-layer CIN
- -10 J/kg
- Mixed-layer LCL
- 632 m above ground
- 0-6 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 119 m²/s²
- 0-3 km storm-relative helicity
- 176 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
The text
As transmitted.
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</html>SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 17, 3:42 PM EDT | Tornado Watch | SPC | Anne Arundel, Calvert, Charles, Prince George's, Saint Mary's | 4 hr |
| Sep 17, 7:09 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Calvert, Charles, Prince George's, Saint Mary's, Talbot and 1 more | 2 hr |
| Sep 17, 10:28 AM EDT | Mesoscale Discussion | SPC | Amelia, Brunswick, Buckingham, Charlotte, Chesterfield, Cumberland and 18 more | 2 hr |
Nearby
Mesoscale Discussions in Virginia, 2018Mesoscale Discussions in Maryland, 2018Every mesoscale discussion in 2018
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.