Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 264, NWS State College, PA

September 1, 2021Lancaster County, Pennsylvania

NWS State College, PA issued this severe thunderstorm warning at Sep 1, 2021, 4:21 PM EDT for Lancaster County, Pennsylvania. It was in force for 39 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Sep 1, 2021, 4:21 PM EDT (20:21 UTC)
Expired
Sep 1, 2021, 5:00 PM EDT
In force
39 min
Issued by
NWS State College, PA
Area
Storm-based polygon
Tornado
Possible
Hail
0.75 in
Wind
60.0 mph

County Lancaster County, PA

The radar

The Dover AFB radar (KDOX), 135 km from the middle of the area, began a volume at 20:22 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.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

IssuedProductOfficeLasted
Sep 1, 12:40 PM EDTTornado WatchSPC9 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.4 hours before the alert went out and 161 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, Washington/Dulle, VA at 12:00Z on 2021-09-01Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 558 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 2021-09-01The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 122 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
558 J/kg
Mixed-layer CIN
-21 J/kg
Mixed-layer LCL
575 m above ground
0-6 km bulk shear
48 kt
0-1 km storm-relative helicity
122 m²/s²
0-3 km storm-relative helicity
223 m²/s²
Significant tornado parameter
0.4
Supercell composite
2.6

Open this sounding in Storm Lab

The text

As transmitted.

461 
WUUS51 KCTP 012021
SVRCTP
PAC071-012100-
/O.NEW.KCTP.SV.W.0264.210901T2021Z-210901T2100Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service State College PA
421 PM EDT Wed Sep 1 2021

The National Weather Service in State College PA has issued a

* Severe Thunderstorm Warning for...
  Eastern Lancaster County in south central Pennsylvania...

* Until 500 PM EDT.

* At 421 PM EDT, a severe thunderstorm was located over Homeville,
  moving northeast at 50 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
  Ephrata, Willow Street, New Holland, Leola, Paradise, Reamstown,
  Strasburg, Quarryville, Gap, Adamstown, Terre Hill, Churchtown,
  Leacock, Bareville, Smithville, Bowmansville, Lampeter,
  Intercourse, Christiana and Fivepointville.

This includes The Pennsylvania Turnpike from mile markers 285 to 295.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 1000 PM EDT for south central
Pennsylvania.

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

For your protection move to an interior room on the lowest floor of a
building.

Very heavy rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

A Tornado Watch remains in effect until 1000 PM EDT for south central
Pennsylvania.

&&

LAT...LON 3995 7632 4027 7608 4014 7587 4010 7594
      4004 7594 3997 7599 3993 7600 3987 7599
      3987 7600 3985 7602 3983 7602 3982 7604
      3981 7603 3978 7606
TIME...MOT...LOC 2021Z 204DEG 41KT 3989 7600 

TORNADO...POSSIBLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Colbert

The office that day

Everything else NWS State College, PA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 1, 8:54 AM EDTFlash Flood Warning Considerable damage threatCTPBedford, Blair, Cambria, Centre, Clearfield, Fulton and 3 more8 hr
Sep 1, 9:37 AM EDTFlash Flood Warning Considerable damage threatCTPCambria, Clearfield, Somerset6 hr
Sep 1, 9:45 AM EDTAreal Flood AdvisoryCTPAdams, Columbia, Cumberland, Dauphin, Franklin, Juniata and 10 more2 hr
Sep 1, 11:04 AM EDTRiver Flood WarningCTPSnyder, Union17 hr
Sep 1, 11:04 AM EDTRiver Flood WarningCTPCambria17 hr
Sep 1, 11:04 AM EDTRiver Flood WarningCTPHuntingdon23 hr
Sep 1, 11:04 AM EDTRiver Flood WarningCTPJuniata, Mifflin20 hr
Sep 1, 11:04 AM EDTRiver Flood WarningCTPBedford, Huntingdon30 hr
Sep 1, 11:04 AM EDTRiver Flood WarningCTPDauphin55 hr
Sep 1, 12:04 PM EDTFlash Flood Warning Considerable damage threatCTPAdams, Columbia, Cumberland, Dauphin, Franklin, Juniata and 10 more6 hr
Sep 1, 1:09 PM EDTFlash Flood Warning EmergencyCatastrophic damage threatCTPCambria5 hr
Sep 1, 2:07 PM EDTSevere Thunderstorm WarningCTPAdams53 min
Sep 1, 2:28 PM EDTSevere Thunderstorm WarningCTPYork77 min
Sep 1, 3:05 PM EDTTornado WarningCTPYork23 min
Sep 1, 3:25 PM EDTSevere Thunderstorm WarningCTPLancaster, York35 min
Sep 1, 3:34 PM EDTAreal Flood WarningCTPCambria, Clearfield, Somerset6 hr
Sep 1, 4:24 PM EDTFlash Flood Warning EmergencyCatastrophic damage threatCTPAdams, York4 hr
Sep 1, 4:40 PM EDTAreal Flood WarningCTPBedford, Blair, Cambria, Centre, Clearfield, Franklin and 4 more6 hr
Sep 1, 5:41 PM EDTAreal Flood WarningCTPAdams, Centre, Columbia, Cumberland, Dauphin, Franklin and 15 more14 hr

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2021Every severe thunderstorm warning 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.