Alert archive / Virginia / Severe Thunderstorm Watches in 2017
Severe Thunderstorm Watch 455
The Storm Prediction Center issued this severe thunderstorm watch at Aug 18, 2017, 2:27 PM EDT for 7 states. It was in force for 9 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 18, 2017, 2:27 PM EDT (18:27 UTC)
- Expired
- Aug 18, 2017, 11:00 PM EDT
- In force
- 9 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 60 kt
All 132 counties
Greater Bridgeport Planning Region, CT, Northwest Hills Planning Region, CT, Kent County, DE, New Castle County, DE, Sussex County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline 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, Somerset County, MD, Talbot County, MD, Washington County, MD, Wicomico County, MD, Worcester County, MD, Atlantic County, NJ, Bergen County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Essex County, NJ, Gloucester County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Passaic County, NJ, Salem County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Bronx County, NY, Columbia County, NY, Delaware County, NY, Dutchess County, NY, Greene County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Orange County, NY, Putnam County, NY, Queens County, NY, Richmond County, NY, Rockland County, NY, Sullivan County, NY, Ulster County, NY, Westchester County, NY, Adams County, PA, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Franklin County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Monroe County, PA, Montgomery County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Pike County, PA, Schuylkill County, PA, Wayne County, PA, Wyoming County, PA, York County, PA, Accomack County, VA, Arlington County, VA, Charles City County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Hampton, VA, City of Manassas, VA, City of Manassas Park, VA, City of Newport News, VA, City of Petersburg, VA, City of Poquoson, VA, City of Williamsburg, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Gloucester County, VA, Greene County, VA, James City County, VA, King and Queen County, VA, King George County, VA, King William County, VA, Lancaster County, VA, Loudoun County, VA, Madison County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Orange County, VA, Prince George County, VA, Prince William County, VA, Rappahannock County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, York County, VA
The radar
The Philadelphia radar (KDIX), 123 km from the middle of the area, began a volume at 18:28 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 10%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
36 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 18, 2:32 PM EDT | Severe Thunderstorm Warning | CTP | Lebanon | 43 min |
| Aug 18, 2:33 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Lehigh | 42 min |
| Aug 18, 2:36 PM EDT | Severe Thunderstorm Warning | CTP | Cumberland, Dauphin, Juniata, Perry, York | 54 min |
| Aug 18, 3:46 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Lehigh, Montgomery, Northampton | 44 min |
| Aug 18, 4:02 PM EDT | Flash Flood Warning | PHI | Berks | 4 hr |
| Aug 18, 4:24 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Bucks, Montgomery | 51 min |
| Aug 18, 4:29 PM EDT | Severe Thunderstorm Warning | PHI | Cecil | 61 min |
| Aug 18, 4:35 PM EDT | Severe Thunderstorm Warning | LWX | Baltimore, Harford | 55 min |
| Aug 18, 4:38 PM EDT | Severe Thunderstorm Warning | CTP | Lancaster | 52 min |
| Aug 18, 5:03 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 42 min |
| Aug 18, 5:07 PM EDT | Flash Flood Warning | LWX | Baltimore, Howard, City of Baltimore | 3 hr |
| Aug 18, 5:10 PM EDT | Flash Flood Warning | LWX | Harford | 4 hr |
| Aug 18, 5:11 PM EDT | Severe Thunderstorm Warning | PHI | Hunterdon, Mercer, Somerset | 49 min |
| Aug 18, 5:14 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Baltimore, Harford, Howard, City of Baltimore | 91 min |
| Aug 18, 5:29 PM EDT | Severe Thunderstorm Warning | LWX | Charles | 46 min |
| Aug 18, 5:32 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Howard, Montgomery, Prince George's | 73 min |
| Aug 18, 5:39 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 66 min |
| Aug 18, 5:46 PM EDT | Severe Thunderstorm Warning | PHI | Hunterdon, Morris, Somerset | 44 min |
| Aug 18, 5:54 PM EDT | Severe Thunderstorm Warning | PHI | Burlington, Mercer, Middlesex, Monmouth | 66 min |
| Aug 18, 5:54 PM EDT | Severe Thunderstorm Warning | OKX | Orange | 51 min |
| Aug 18, 5:59 PM EDT | Severe Thunderstorm Warning | LWX | Calvert, Charles, Prince George's, Saint Mary's | 46 min |
| Aug 18, 6:10 PM EDT | Severe Thunderstorm Warning | PHI | Kent | 65 min |
| Aug 18, 6:34 PM EDT | Flash Flood Warning | LWX | Montgomery, Prince George's | 3 hr |
| Aug 18, 6:42 PM EDT | Severe Thunderstorm Warning | LWX | Calvert, Charles, Saint Mary's | 63 min |
| Aug 18, 6:58 PM EDT | Severe Thunderstorm Warning | PHI | Burlington, Camden, Ocean | 29 min |
| Aug 18, 7:00 PM EDT | Severe Thunderstorm Warning | PHI | Burlington, Mercer, Middlesex, Monmouth, Ocean | 60 min |
| Aug 18, 7:07 PM EDT | Severe Thunderstorm Warning | PHI | Kent, New Castle, Sussex | 53 min |
| Aug 18, 7:13 PM EDT | Severe Thunderstorm Warning | AKQ | Caroline, Essex, Hanover, King and Queen, Richmond, Westmoreland | 47 min |
| Aug 18, 7:14 PM EDT | Flash Flood Warning | LWX | Harford | 3 hr |
| Aug 18, 7:36 PM EDT | Flash Flood Warning | LWX | Calvert, Charles, Saint Mary's | 4 hr |
| Aug 18, 7:49 PM EDT | Severe Thunderstorm Warning | PHI | Atlantic, Cape May, Cumberland, Gloucester | 35 min |
| Aug 18, 7:51 PM EDT | Severe Thunderstorm Warning | LWX | Calvert, Charles, Saint Mary's | 84 min |
| Aug 18, 7:53 PM EDT | Severe Thunderstorm Warning | PHI | Kent, Sussex | 48 min |
| Aug 18, 7:53 PM EDT | Severe Thunderstorm Warning | AKQ | Essex, King and Queen, Lancaster, Northumberland, Richmond, Westmoreland | 52 min |
| Aug 18, 7:58 PM EDT | Severe Thunderstorm Warning | AKQ | Essex, Gloucester, Hanover, Henrico, King and Queen, King William and 5 more | 62 min |
| Aug 18, 9:17 PM EDT | Severe Thunderstorm Warning | AKQ | Somerset, Wicomico, Worcester | 43 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Brookhaven, NY (KOKX), launched 12:00Z, 6.5 hours before the alert went out and 222 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
- 1073 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 147 m²/s²
- 0-3 km storm-relative helicity
- 215 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 18, 4:34 PM EDT | Mesoscale Discussion | SPC | 86 min | |
| Aug 18, 1:54 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 2 hr |
| Aug 17, 8:00 PM EDT | Mesoscale Discussion | SPC | Crawford, Lawrence, Mercer, Venango | 90 min |
Nearby
Severe Thunderstorm Watches in Virginia, 2017Severe Thunderstorm Watches in Pennsylvania, 2017Severe Thunderstorm Watches in Maryland, 2017Every severe thunderstorm watch 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.