Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2017
Severe Thunderstorm Watch 480
The Storm Prediction Center issued this severe thunderstorm watch at Sep 5, 2017, 3:26 PM EDT for 5 states. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 5, 2017, 3:26 PM EDT (19:26 UTC)
- Expired
- Sep 5, 2017, 8:02 PM EDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 41 counties
Baltimore County, MD, Carroll County, MD, Cecil County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Morris County, NJ, Somerset County, NJ, Sussex County, NJ, Warren County, NJ, Adams County, PA, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Franklin County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Perry County, PA, Philadelphia County, PA, Schuylkill County, PA, York County, PA, City of Winchester, VA, Clarke County, VA, Frederick County, VA, Loudoun County, VA, Berkeley County, WV, Jefferson County, WV
The radar
The Philadelphia radar (KDIX), 136 km from the middle of the area, began a volume at 19:29 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
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
15 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 5, 3:31 PM EDT | Severe Thunderstorm Warning | LWX | Clarke, Frederick, City of Winchester | 44 min |
| Sep 5, 3:51 PM EDT | Severe Thunderstorm Warning | LWX | Carroll, Frederick, Washington | 39 min |
| Sep 5, 3:51 PM EDT | Severe Thunderstorm Warning | CTP | Adams, Cumberland, York | 84 min |
| Sep 5, 4:07 PM EDT | Tornado Warning | CTP | Adams, York | 38 min |
| Sep 5, 4:08 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Carbon, Lehigh, Northampton | 52 min |
| Sep 5, 4:16 PM EDT | Severe Thunderstorm Warning | LWX | Clarke, Loudoun | 29 min |
| Sep 5, 4:35 PM EDT | Severe Thunderstorm Warning | CTP | Cumberland, Dauphin, Lancaster, Lebanon, York | 85 min |
| Sep 5, 4:46 PM EDT | Severe Thunderstorm Warning | LWX | Clarke, Fauquier, Loudoun, Warren | 44 min |
| Sep 5, 4:54 PM EDT | Severe Thunderstorm Warning | PHI | Warren | 51 min |
| Sep 5, 5:14 PM EDT | Flash Flood Warning | PHI | Berks | 4 hr |
| Sep 5, 5:19 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Chester, Montgomery | 56 min |
| Sep 5, 5:30 PM EDT | Flash Flood Warning | PHI | Berks | 4 hr |
| Sep 5, 5:34 PM EDT | Severe Thunderstorm Warning | LWX | Clarke, Fauquier, Loudoun, Warren | 26 min |
| Sep 5, 5:49 PM EDT | Severe Thunderstorm Warning | PHI | Berks, Bucks, Lehigh, Montgomery, Northampton | 41 min |
| Sep 5, 6:26 PM EDT | Severe Thunderstorm Warning | PHI | Hunterdon, Morris, Somerset, Sussex, Warren | 49 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 7.4 hours before the alert went out and 180 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
- 4 J/kg
- Mixed-layer CIN
- -324 J/kg
- Mixed-layer LCL
- 1529 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 8 m²/s²
- 0-3 km storm-relative helicity
- 79 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 5, 5:00 PM EDT | Mesoscale Discussion | SPC | New Castle | 90 min |
| Sep 5, 2:31 PM EDT | Mesoscale Discussion | SPC | Carroll, Frederick, Howard, Montgomery, Washington | 59 min |
| Sep 4, 10:26 PM EDT | Mesoscale Discussion | SPC | Erie | 64 min |
Nearby
Severe Thunderstorm Watches in Pennsylvania, 2017Severe Thunderstorm Watches in Maryland, 2017Severe Thunderstorm Watches in New Jersey, 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.