Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2007
Severe Thunderstorm Watch 573
The Storm Prediction Center issued this severe thunderstorm watch at Aug 9, 2007, 9:47 AM EDT for 4 states. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 9, 2007, 9:47 AM EDT (13:47 UTC)
- Expired
- Aug 9, 2007, 4:00 PM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 40 counties
Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Adams County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Centre County, PA, Clearfield County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Mifflin County, PA, Perry County, PA, Snyder County, PA, Somerset County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, Clarke County, VA, Fairfax County, VA, Loudoun County, VA, Berkeley County, WV, Jefferson County, WV, Morgan County, WV
The radar
The Sterling radar (KLWX), 101 km from the middle of the area, began a volume at 13:47 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
- 5%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- 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
8 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 9, 10:08 AM EDT | Severe Thunderstorm Warning | CTP | Fulton, Huntingdon | 67 min |
| Aug 9, 10:33 AM EDT | Severe Thunderstorm Warning | CTP | Bedford | 27 min |
| Aug 9, 10:38 AM EDT | Severe Thunderstorm Warning | CTP | Franklin | 67 min |
| Aug 9, 10:47 AM EDT | Severe Thunderstorm Warning | LWX | Washington | 73 min |
| Aug 9, 10:51 AM EDT | Severe Thunderstorm Warning | CTP | Cumberland, Perry | 54 min |
| Aug 9, 11:18 AM EDT | Severe Thunderstorm Warning | LWX | Carroll, Frederick | 72 min |
| Aug 9, 11:28 AM EDT | Severe Thunderstorm Warning | CTP | Adams | 47 min |
| Aug 9, 3:47 PM EDT | Severe Thunderstorm Warning | CTP | Cambria, Somerset | 58 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, 1.8 hours before the alert went out and 106 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
- 547 J/kg
- Mixed-layer CIN
- -121 J/kg
- Mixed-layer LCL
- 1213 m above ground
- 0-6 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 40 m²/s²
- 0-3 km storm-relative helicity
- 117 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 3.4
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 9, 8:47 AM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Carroll, Cecil, Frederick, Harford and 6 more | 58 min |
| Aug 9, 12:35 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Caroline, Cecil, Dorchester and 11 more | 85 min |
| Aug 9, 12:48 PM EDT | Severe Thunderstorm Watch | SPC | Caroline, Cecil, Dorchester, Kent, Queen Anne's, Somerset and 3 more | 3 hr |
| Aug 9, 1:22 PM EDT | Severe Thunderstorm Watch | SPC | Garrett | 7 hr |
| Aug 9, 2:25 PM EDT | Mesoscale Discussion | SPC | Calvert, Charles, Dorchester, Saint Mary's, Somerset, Wicomico | 2 hr |
| Aug 9, 2:41 PM EDT | Mesoscale Discussion | SPC | Allegany, Anne Arundel, Calvert, Charles, Dorchester, Frederick and 9 more | 94 min |
| Aug 9, 7:23 PM EDT | Mesoscale Discussion | SPC | Allegany, Anne Arundel, Baltimore, Calvert, Caroline, Carroll and 16 more | 67 min |
| Aug 9, 11:54 AM EDT | Mesoscale Discussion | SPC | Allegheny, Beaver, Butler, Fayette, Greene, Lawrence and 3 more | 2 hr |
| Aug 9, 5:03 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Butler, Fayette, Greene and 4 more | 87 min |
Nearby
Severe Thunderstorm Watches in Pennsylvania, 2007Severe Thunderstorm Watches in Maryland, 2007Severe Thunderstorm Watches in Virginia, 2007Every severe thunderstorm watch in 2007
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.