Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 240, NWS State College, PA

August 18, 20214 counties in Pennsylvania

NWS State College, PA issued this severe thunderstorm warning at Aug 18, 2021, 3:36 PM EDT for 4 counties in Pennsylvania. It was in force for 24 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 18, 2021, 3:36 PM EDT (19:36 UTC)
Expired: Aug 18, 2021, 4:00 PM EDT
In force: 24 min
Issued by: NWS State College, PA
Area: Storm-based polygon
Tornado: Possible
Hail: 0.75 in
Wind: 60.0 mph

Counties Cumberland County, PA, Dauphin County, PA, Lancaster County, PA, York County, PA

The radar

The Sterling radar (KLWX), 128 km from the middle of the area, began a volume at 19:37 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 was reported inside it

Time	Report	Where	Remark
Aug 18, 3:39 PM EDT	TSTM WND DMG	2 Wsw Siddonsburg, PA	TREES DOWN ON FILEYS ROAD.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

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

Issued	Product	Office	Lasted
Aug 18, 11:37 AM EDT	Tornado Watch	SPC	11 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 7.6 hours before the alert went out and 128 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 1011 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 592 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 151 m²/s²
0-3 km storm-relative helicity: 175 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 4.6

Open this sounding in Storm Lab

The text

As transmitted.

946 
WUUS51 KCTP 181936
SVRCTP
PAC041-043-071-133-182000-
/O.NEW.KCTP.SV.W.0240.210818T1936Z-210818T2000Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service State College PA
336 PM EDT Wed Aug 18 2021

The National Weather Service in State College PA has issued a

* Severe Thunderstorm Warning for...
  West central Lancaster County in south central Pennsylvania...
  Northwestern York County in south central Pennsylvania...
  Southeastern Dauphin County in south central Pennsylvania...
  East central Cumberland County in south central Pennsylvania...

* Until 400 PM EDT.

* At 336 PM EDT, severe thunderstorms were located along a line
  extending from Siddonsburg to 6 miles northwest of Weigelstown to
  near Dover to East Berlin, moving east at 40 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Harrisburg, York, Lower Allen, Hershey, Colonial Park, Weigelstown,
  Elizabethtown, Progress, Mechanicsburg, Middletown, Camp Hill,
  Palmyra, New Cumberland, Steelton, Lemoyne, Hummelstown, Shiloh,
  East York, Stonybrook-Wilshire and West York.

This includes the following Interstates...
 The Pennsylvania Turnpike from mile markers 234 to 259.
 Interstate 83 from mile markers 18 to 48.
 Interstate 283 from mile markers 0 to 2.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 800 PM EDT for south central
Pennsylvania.

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

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

&&

LAT...LON 3990 7698 3992 7697 3994 7697 3997 7699
      4001 7700 4016 7712 4036 7663 4014 7654
      4005 7653 3998 7659 3989 7698
TIME...MOT...LOC 1936Z 249DEG 35KT 4012 7699 4004 7693 3997 7692 3993
7698

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

$$

Jurewicz

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 18, 9:50 AM EDT	Special Weather Statement	CTP	Bedford	55 min
Aug 18, 10:25 AM EDT	Areal Flood Advisory	CTP	Bedford	3 hr
Aug 18, 10:32 AM EDT	Severe Thunderstorm Warning	CTP	Bedford, Blair	43 min
Aug 18, 10:53 AM EDT	Special Weather Statement	CTP	Cambria	37 min
Aug 18, 10:57 AM EDT	Special Weather Statement	CTP	Bedford	18 min
Aug 18, 11:15 AM EDT	Special Weather Statement	CTP	Blair, Cambria	30 min
Aug 18, 11:33 AM EDT	Areal Flood Advisory	CTP	Blair, Cambria	3 hr
Aug 18, 12:04 PM EDT	Areal Flood Advisory	CTP	Bedford	2 hr
Aug 18, 12:11 PM EDT	Special Weather Statement	CTP	Blair	34 min
Aug 18, 12:26 PM EDT	Special Weather Statement	CTP	Schuylkill	34 min
Aug 18, 12:35 PM EDT	Flash Flood Warning Considerable damage threat	CTP	Bedford, Blair, Huntingdon	3 hr
Aug 18, 12:39 PM EDT	Special Weather Statement	CTP	Cumberland	36 min
Aug 18, 12:54 PM EDT	Severe Thunderstorm Warning	CTP	Cumberland, Perry	36 min
Aug 18, 1:01 PM EDT	Special Weather Statement	CTP	Huntingdon	44 min
Aug 18, 1:15 PM EDT	Special Weather Statement	CTP	Juniata, Mifflin	30 min
Aug 18, 1:31 PM EDT	Severe Thunderstorm Warning	CTP	Juniata, Perry	44 min
Aug 18, 1:37 PM EDT	Flash Flood Warning Considerable damage threat	CTP	Blair, Centre, Huntingdon	82 min
Aug 18, 2:00 PM EDT	Special Weather Statement	CTP	Snyder	30 min
Aug 18, 2:02 PM EDT	Tornado Warning	CTP	Centre, Huntingdon	28 min
Aug 18, 2:12 PM EDT	Severe Thunderstorm Warning	CTP	Centre, Clinton	33 min
Aug 18, 2:26 PM EDT	Special Weather Statement	CTP	Cumberland, Perry	34 min
Aug 18, 2:29 PM EDT	Special Weather Statement	CTP	Centre	31 min
Aug 18, 2:36 PM EDT	Severe Thunderstorm Warning	CTP	Cumberland, Perry	39 min
Aug 18, 3:03 PM EDT	Special Weather Statement	CTP	Cumberland	42 min
Aug 18, 3:10 PM EDT	Tornado Warning	CTP	Adams, York	40 min
Aug 18, 3:17 PM EDT	Areal Flood Warning	CTP	Bedford, Blair, Huntingdon	118 min
Aug 18, 3:56 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin, Juniata, Northumberland, Perry, Snyder	34 min
Aug 18, 4:03 PM EDT	Special Weather Statement	CTP	Dauphin	42 min
Aug 18, 4:05 PM EDT	Severe Thunderstorm Warning	CTP	Franklin, Fulton	40 min
Aug 18, 4:30 PM EDT	Areal Flood Advisory	CTP	Juniata, Perry, Snyder	4 hr
Aug 18, 4:30 PM EDT	Special Weather Statement	CTP	Snyder	30 min
Aug 18, 4:39 PM EDT	Severe Thunderstorm Warning	CTP	Franklin	36 min
Aug 18, 4:42 PM EDT	Areal Flood Advisory	CTP	Fulton, Huntingdon	2 hr
Aug 18, 4:48 PM EDT	Areal Flood Advisory	CTP	Cameron, Clinton, Lycoming, Potter, Tioga	5 hr
Aug 18, 5:10 PM EDT	Severe Thunderstorm Warning	CTP	Adams, Cumberland, Franklin, Perry, York	35 min
Aug 18, 5:18 PM EDT	Severe Thunderstorm Warning	CTP	Juniata, Mifflin	45 min
Aug 18, 5:31 PM EDT	Severe Thunderstorm Warning	CTP	Dauphin	74 min
Aug 18, 5:35 PM EDT	Special Weather Statement	CTP	Lancaster	25 min
Aug 18, 5:35 PM EDT	Severe Thunderstorm Warning	CTP	Adams	40 min
Aug 18, 5:38 PM EDT	Severe Thunderstorm Warning	CTP	Adams, Cumberland, York	37 min
Aug 18, 6:13 PM EDT	Severe Thunderstorm Warning	CTP	Adams, Cumberland, Dauphin, Lancaster, Perry, York	47 min
Aug 18, 6:37 PM EDT	Areal Flood Advisory	CTP	Adams, Cumberland, Franklin, York	2 hr
Aug 18, 6:47 PM EDT	Severe Thunderstorm Warning	CTP	Adams, Dauphin, Lancaster, Lebanon, Schuylkill, York	43 min
Aug 18, 6:56 PM EDT	Special Weather Statement	CTP	Schuylkill	19 min
Aug 18, 7:23 PM EDT	Areal Flood Advisory	CTP	Columbia, Sullivan	2 hr
Aug 18, 7:30 PM EDT	Severe Thunderstorm Warning	CTP	Lancaster, York	45 min
Aug 18, 7:37 PM EDT	Flash Flood Warning Considerable damage threat	CTP	Schuylkill	2 hr
Aug 18, 7:40 PM EDT	Flash Flood Warning	CTP	Dauphin, Lancaster, York	3 hr

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2021 Every 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.