Alert archive / Pennsylvania / Severe Thunderstorm Warnings in 2026

Severe Thunderstorm Warning 37, NWS Philadelphia/Mount Holly

May 20, 2026New Castle County, Delaware; Chester County, Delaware County, Pennsylvania

NWS Philadelphia/Mount Holly issued this severe thunderstorm warning at May 20, 2026, 4:50 PM EDT for New Castle County, Delaware; Chester County, Delaware County, Pennsylvania. It was in force for 40 min. 2 reports 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: May 20, 2026, 4:50 PM EDT (20:50 UTC)
Expired: May 20, 2026, 5:30 PM EDT
In force: 40 min
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties New Castle County, DE, Chester County, PA, Delaware County, PA

The radar

The Dover AFB radar (KDOX), 117 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 was reported inside it

Time	Report	Where	Remark
May 20, 5:12 PM EDT	TSTM WND DMG	1 Ene Lenape, PA	Picture sent in of a large pine tree down. Time estimated from radar.
May 20, 5:12 PM EDT	TSTM WND DMG	1 Ene Lenape, PA	Picture sent in of a large pine tree down. Time estimated from radar.

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
May 20, 2:10 PM EDT	Severe Thunderstorm Watch	SPC	7 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.8 hours before the alert went out and 159 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: 47 J/kg
Mixed-layer CIN: -204 J/kg
Mixed-layer LCL: 1752 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: -79 m²/s²
0-3 km storm-relative helicity: -47 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

211 
WUUS51 KPHI 202050
SVRPHI
DEC003-PAC029-045-202130-
/O.NEW.KPHI.SV.W.0037.260520T2050Z-260520T2130Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mount Holly NJ
450 PM EDT Wed May 20 2026

The National Weather Service in Mount Holly NJ has issued a

* Severe Thunderstorm Warning for...
  Northwestern New Castle County in northern Delaware...
  Southern Chester County in southeastern Pennsylvania...
  Southwestern Delaware County in southeastern Pennsylvania...

* Until 530 PM EDT.

* At 450 PM EDT, a severe thunderstorm was located near Cochranville,
  or 13 miles northwest of Newark, moving east at 15 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Damage to roofs, siding, trees, and power lines is 
           possible.

* Locations impacted include...
  Wilmington, Newark, West Chester, Westtown, Elsmere, Kennett
  Square, Oxford, Parkesburg, West Grove, Newport, Glen Roy,
  Homeville, Cochranville, Stanton, Cheyney, North Star, Talleyville,
  Elam, Mount Vernon, and Marshallton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3977 7606 3981 7603 3983 7604 3983 7602
      3987 7601 3987 7599 3997 7599 3996 7550
      3970 7557 3970 7579 3972 7579 3972 7608
TIME...MOT...LOC 2050Z 276DEG 12KT 3984 7590 

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

$$

Fitzsimmons

1 follow-up statement

471 
WWUS51 KPHI 202118
SVSPHI

Severe Weather Statement
National Weather Service Mount Holly NJ
518 PM EDT Wed May 20 2026

DEC003-PAC029-045-202130-
/O.CON.KPHI.SV.W.0037.000000T0000Z-260520T2130Z/
New Castle DE-Chester PA-Delaware PA-
518 PM EDT Wed May 20 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 PM EDT
FOR NORTHWESTERN NEW CASTLE...SOUTHERN CHESTER AND SOUTHWESTERN
DELAWARE COUNTIES...

At 518 PM EDT, a severe thunderstorm was located over West Grove, or
10 miles north of Newark, moving east at 15 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Damage to roofs, siding, trees, and power lines is 
         possible.

Locations impacted include...
Wilmington, Newark, West Chester, Westtown, Elsmere, Kennett Square,
Oxford, Parkesburg, West Grove, Newport, Cochranville, Stanton,
Cheyney, North Star, Talleyville, Elam, Marshallton, Pike Creek,
Ashland, and Greenville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3972 7600 3997 7593 3996 7550 3970 7557
      3970 7571 3971 7579 3972 7579
TIME...MOT...LOC 2118Z 275DEG 13KT 3983 7578 

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

$$

Fitzsimmons

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 20, 5:18 PM EDT	Severe Thunderstorm Warning	PHI	Kent, New Castle	42 min
May 20, 5:29 PM EDT	Severe Thunderstorm Warning	PHI	New Castle	46 min
May 20, 5:35 PM EDT	Severe Thunderstorm Warning	PHI	New Castle	40 min
May 19, 8:04 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	25 min
May 20, 3:57 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Lehigh	48 min
May 20, 4:00 PM EDT	Severe Thunderstorm Warning	PHI	Berks	45 min
May 20, 4:29 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Chester, Montgomery	46 min
May 20, 4:43 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Lehigh, Northampton	47 min
May 20, 4:46 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Lehigh, Montgomery	44 min
May 20, 5:10 PM EDT	Severe Thunderstorm Warning	PHI	Chester, Delaware, Montgomery, Philadelphia	50 min
May 20, 5:15 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Chester, Montgomery, Philadelphia	45 min
May 20, 5:24 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Northampton	51 min
May 20, 5:40 PM EDT	Flash Flood Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	3 hr
May 20, 5:41 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	49 min
May 20, 5:52 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Montgomery, Philadelphia	38 min
May 20, 6:01 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Montgomery, Philadelphia	44 min
May 20, 6:09 PM EDT	Severe Thunderstorm Warning	PHI	Delaware, Philadelphia	46 min

Nearby

Severe Thunderstorm Warnings in Pennsylvania, 2026 Severe Thunderstorm Warnings in Delaware, 2026 Every severe thunderstorm warning in 2026

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.