Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 330
The Storm Prediction Center issued this severe thunderstorm watch at Jun 30, 2021, 4:51 PM EDT for 4 counties in Maryland; 9 counties in Pennsylvania; 5 counties in West Virginia. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 30, 2021, 4:51 PM EDT (20:51 UTC)
- Expired
- Jun 30, 2021, 8:14 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 60 kt
Counties Allegany County, MD, Carroll County, MD, Frederick County, MD, Washington County, MD, Adams County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Lancaster County, PA, Lebanon County, PA, Perry County, PA, Schuylkill County, PA, York County, PA, Berkeley County, WV, Hampshire County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV
The radar
The Sterling radar (KLWX), 118 km from the middle of the area, began a volume at 20:52 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
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 40%
Warnings issued inside it
5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 30, 4:55 PM EDT | Severe Thunderstorm Warning | LWX | Allegany, Washington | 21 min |
| Jun 30, 5:11 PM EDT | Severe Thunderstorm Warning | LWX | Hampshire, Morgan | 34 min |
| Jun 30, 5:24 PM EDT | Severe Thunderstorm Warning | CTP | Franklin, Fulton | 48 min |
| Jun 30, 5:32 PM EDT | Severe Thunderstorm Warning | LWX | Berkeley, Morgan | 23 min |
| Jun 30, 6:27 PM EDT | Severe Thunderstorm Warning | CTP | Cumberland | 48 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, 8.9 hours before the alert went out and 120 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
- 40 J/kg
- Mixed-layer CIN
- -217 J/kg
- Mixed-layer LCL
- 1553 m above ground
- 0-6 km bulk shear
- 14 kt
- 0-1 km storm-relative helicity
- -26 m²/s²
- 0-3 km storm-relative helicity
- 76 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
316 WWUS20 KWNS 302045 SEL0 SPC WW 302045 MDZ000-PAZ000-VAZ000-WVZ000-010200- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 330 NWS Storm Prediction Center Norman OK 445 PM EDT Wed Jun 30 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Maryland South central Pennsylvania Extreme northern Virginia The eastern West Virginia Panhandle * Effective this Wednesday afternoon and evening from 445 PM until 1000 PM EDT. * Primary threats include... Isolated damaging wind gusts to 70 mph possible SUMMARY...A couple of storm clusters may persist and spread east-northeastward through this evening, along an immediately southeast of an outflow boundary approaching southern Pennsylvania. The storm environment favors occasional downbursts with wind damage. The severe thunderstorm watch area is approximately along and 40 statute miles north and south of a line from 30 miles east northeast of Harrisburg PA to 40 miles south southwest of Altoona PA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 326...WW 327...WW 328...WW 329... AVIATION...A few severe thunderstorms with hail surface and aloft to 0.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 26020. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 30, 4:41 PM EDT | Mesoscale Discussion | SPC | Allegany, Baltimore, Carroll, Frederick, Garrett, Howard and 2 more | 2 hr |
| Jun 30, 6:58 PM EDT | Mesoscale Discussion | SPC | Carroll, Frederick, Montgomery | 92 min |
| Jun 30, 11:30 AM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Beaver, Blair, Butler, Cambria and 23 more | 2 hr |
| Jun 30, 11:47 AM EDT | Severe Thunderstorm Watch | SPC | Allegheny, Armstrong, Beaver, Butler, Clarion, Fayette and 9 more | 7 hr |
| Jun 30, 12:46 PM EDT | Severe Thunderstorm Watch | SPC | Bedford, Blair, Cambria, Cameron, Centre, Clearfield and 20 more | 7 hr |
| Jun 30, 2:16 PM EDT | Mesoscale Discussion | SPC | Carbon, Lackawanna, Luzerne, Monroe, Pike, Wayne and 1 more | 119 min |
| Jun 30, 3:21 PM EDT | Severe Thunderstorm Watch | SPC | Berks, Bradford, Carbon, Lackawanna, Lehigh, Luzerne and 6 more | 7 hr |
| Jun 30, 3:29 PM EDT | Mesoscale Discussion | SPC | Allegheny, Armstrong, Bedford, Blair, Cambria, Centre and 16 more | 2 hr |
| Jun 30, 4:48 PM EDT | Mesoscale Discussion | SPC | Lackawanna, Susquehanna, Wayne | 87 min |
Nearby
Severe Thunderstorm Watches in Pennsylvania, 2021Severe Thunderstorm Watches in West Virginia, 2021Severe Thunderstorm Watches in Maryland, 2021Every severe thunderstorm watch in 2021
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.