Alert archive / Pennsylvania / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 246

April 27, 201132 counties in Pennsylvania

The Storm Prediction Center issued this severe thunderstorm watch at Apr 27, 2011, 11:50 PM EDT for 32 counties in Pennsylvania. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Apr 27, 2011, 11:50 PM EDT (03:50 UTC)
Expired
Apr 28, 2011, 7:00 AM EDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.5 in
Strongest gust expected
60 kt
All 32 counties

Adams County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Elk County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lycoming County, PA, McKean County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Potter County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Sullivan County, PA, Tioga County, PA, Union County, PA, York County, PA

The radar

The State College radar (KCCX), 28 km from the middle of the area, began a volume at 03:53 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
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
30%
One or more gusts of 65 knots or more
30%
Ten or more severe hail reports
30%
One or more hailstones of 2 inches or more
20%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

19 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 28, 12:26 AM EDTSevere Thunderstorm WarningCTPBedford, Somerset64 min
Apr 28, 12:33 AM EDTSevere Thunderstorm WarningCTPLycoming, Tioga57 min
Apr 28, 1:21 AM EDTSevere Thunderstorm WarningCTPBedford, Blair, Huntingdon, Mifflin39 min
Apr 28, 1:35 AM EDTSevere Thunderstorm WarningCTPLycoming, Sullivan25 min
Apr 28, 1:42 AM EDTFlash Flood WarningCTPCameron, Clinton, Lycoming, Potter, Sullivan, Tioga4 hr
Apr 28, 1:44 AM EDTFlash Flood WarningCTPBedford, Blair, Cambria, Fulton, Huntingdon, Somerset4 hr
Apr 28, 2:52 AM EDTSevere Thunderstorm WarningCTPCentre, Clinton, Cumberland, Franklin, Juniata, Mifflin and 3 more53 min
Apr 28, 3:02 AM EDTFlash Flood WarningCTPCentre3 hr
Apr 28, 3:34 AM EDTFlash Flood WarningCTPFranklin3 hr
Apr 28, 3:37 AM EDTSevere Thunderstorm WarningCTPCentre, Clinton, Dauphin, Juniata, Lycoming, Montour and 4 more38 min
Apr 28, 3:46 AM EDTSevere Thunderstorm WarningCTPAdams, Cumberland, Dauphin, Lancaster, Lebanon, Perry and 1 more44 min
Apr 28, 4:00 AM EDTSevere Thunderstorm WarningCTPColumbia, Dauphin, Lycoming, Montour, Northumberland, Schuylkill and 1 more60 min
Apr 28, 4:25 AM EDTFlash Flood WarningCTPAdams, Cumberland, Dauphin, Perry, York7 hr
Apr 28, 4:28 AM EDTSevere Thunderstorm WarningCTPAdams, Cumberland, Dauphin, Lancaster, Lebanon, Schuylkill and 1 more47 min
Apr 28, 5:14 AM EDTSevere Thunderstorm WarningCTPAdams, Cumberland, Franklin, York46 min
Apr 28, 5:35 AM EDTTornado WarningCTPAdams, Cumberland, York25 min
Apr 28, 5:49 AM EDTSevere Thunderstorm WarningCTPDauphin, Lebanon, Schuylkill56 min
Apr 28, 6:13 AM EDTFlash Flood WarningCTPLebanon, Schuylkill4 hr
Apr 28, 6:53 AM EDTSevere Thunderstorm WarningCTPLebanon, Schuylkill37 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

Pittsburgh, PA (KPIT), launched 00:00Z, 3.8 hours before the alert went out and 214 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.

Skew-T log-pSkew-T log-p diagram, Pittsburgh, PA at 00:00Z on 2011-04-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 38 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Pittsburgh, PA at 00:00Z on 2011-04-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 128 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
38 J/kg
Mixed-layer CIN
-123 J/kg
Mixed-layer LCL
1277 m above ground
0-6 km bulk shear
65 kt
0-1 km storm-relative helicity
128 m²/s²
0-3 km storm-relative helicity
134 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 27, 8:15 PM EDTSevere Thunderstorm WatchSPCCaroline, Cecil, Kent, Queen Anne's, Talbot8 hr
Apr 28, 12:27 AM EDTMesoscale DiscussionSPCAllegany, Frederick, Howard, Montgomery, Washington63 min
Apr 28, 12:41 AM EDTTornado WatchSPCAllegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more7 hr
Apr 28, 4:05 AM EDTSevere Thunderstorm WatchSPCCaroline, Cecil, Kent, Queen Anne's, Talbot6 hr
Apr 28, 7:38 AM EDTTornado WatchSPCAnne Arundel, Baltimore, Calvert, Carroll, Charles, Dorchester and 10 more7 hr
Apr 28, 9:45 AM EDTSevere Thunderstorm WatchSPCCaroline, Cecil, Kent, Queen Anne's, Talbot6 hr
Apr 28, 10:44 AM EDTMesoscale DiscussionSPCAnne Arundel, Baltimore, Calvert, Caroline, Carroll, Cecil and 13 more61 min
Apr 28, 11:49 AM EDTMesoscale DiscussionSPCCecil, Kent, Queen Anne's56 min
Apr 28, 2:00 PM EDTMesoscale DiscussionSPCAnne Arundel, Calvert, Caroline, Charles, Dorchester, Kent and 7 more60 min
Apr 28, 2:41 PM EDTTornado WatchSPCDorchester, Somerset, Wicomico, Worcester6 hr
Apr 28, 6:33 PM EDTMesoscale DiscussionSPCDorchester, Saint Mary's, Somerset, Wicomico, Worcester57 min
Apr 27, 9:03 PM EDTMesoscale DiscussionSPCAdams, Bradford, Columbia, Cumberland, Dauphin, Juniata and 9 more57 min
Apr 27, 10:45 PM EDTMesoscale DiscussionSPCBlair, Bradford, Cambria, Carbon, Centre, Clinton and 23 more60 min
Apr 28, 2:20 AM EDTMesoscale DiscussionSPCAdams, Bedford, Berks, Blair, Bradford, Carbon and 31 more55 min
Apr 28, 3:32 AM EDTMesoscale DiscussionSPCAdams, Berks, Bradford, Bucks, Carbon, Chester and 25 more28 min
Apr 28, 6:21 AM EDTMesoscale DiscussionSPCBerks, Bucks, Carbon, Chester, Delaware, Lackawanna and 7 more54 min

Nearby

Severe Thunderstorm Watches in Pennsylvania, 2011Every severe thunderstorm watch in 2011

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.