Alert archive / Pennsylvania / Special Weather Statements in 2021

Special Weather Statement, NWS Philadelphia/Mount Holly

April 21, 2021Chester County, Lehigh County, Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Apr 21, 2021, 12:03 PM EDT for Chester County, Lehigh County, Pennsylvania. It was in force for 42 min. 8 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: Apr 21, 2021, 12:03 PM EDT (16:03 UTC)
Expired: Apr 21, 2021, 12:45 PM EDT
In force: 42 min
Issued by: NWS Philadelphia/Mount Holly

Counties Chester County, PA, Lehigh County, PA

The radar

The Philadelphia radar (KDIX), 115 km from the middle of the area, began a volume at 16:03 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
Apr 21, 12:20 PM EDT	HAIL 0.25	2 Ssw District Twp, PA
Apr 21, 12:22 PM EDT	HAIL 1	1 S Boyertown, PA
Apr 21, 12:30 PM EDT	HAIL 0.25	3 Wnw Uwchlan Twp, PA
Apr 21, 12:35 PM EDT	TSTM WND DMG	1 Ssw Allentown, PA	TREE DOWN ON WIRES NEAR LEHIGH PKWY. TIME ESTIMATED FROM RADAR.
Apr 21, 12:35 PM EDT	HAIL 0.25	Emmaus, PA
Apr 21, 12:50 PM EDT	HAIL 0.25	Collegeville, PA
Apr 21, 12:52 PM EDT	HAIL 0.25	Landenberg, PA
Apr 21, 12:55 PM EDT	HAIL 0.25	Kennett Square, PA

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 4.1 hours before the alert went out and 199 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: 8 J/kg
Mixed-layer CIN: -277 J/kg
Mixed-layer LCL: 1577 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 128 m²/s²
0-3 km storm-relative helicity: 109 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

609 
WWUS81 KPHI 211603
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
1203 PM EDT Wed Apr 21 2021

DEZ001-PAZ060-061-070-101>103-105-211645-
New Castle-Upper Bucks-Lehigh-Western Montgomery-Delaware-Western
Chester-Eastern Chester-Berks-
1203 PM EDT Wed Apr 21 2021

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN NEW
CASTLE...EASTERN BERKS...LEHIGH...NORTHWESTERN MONTGOMERY...WEST
CENTRAL BUCKS...CHESTER AND WEST CENTRAL DELAWARE COUNTIES...

At 1203 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Kutztown to Oxford. Movement was
east at 40 mph.

Wind gusts up to 50 mph and pea size hail are possible with these
storms.

Locations impacted include...
Allentown, Newark, West Chester, Bethlehem, Pottstown, Phoenixville,
Coatesville, Emmaus, Westtown, Northampton, Downingtown, Elsmere,
Kennett Square, Birdsboro, Collegeville, Oxford, Kutztown,
Royersford, Fleetwood and Parkesburg.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 296 and 322.
 Northeast Extension between mile markers 42 and 62.
 Interstate 78 in Pennsylvania between mile markers 41 and 63.
 Interstate 176 in Pennsylvania between mile markers 1 and 5.

If outdoors, consider seeking shelter inside a building.

LAT...LON 3987 7599 3998 7598 4004 7593 4011 7594
      4014 7588 4017 7593 4060 7582 4069 7550
      4066 7548 4067 7544 4062 7538 4058 7541
      4057 7539 4022 7544 3970 7561 3970 7579
      3972 7579 3972 7604
TIME...MOT...LOC 1603Z 253DEG 35KT 4055 7576 3979 7596 

$$

Davis

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 20, 8:48 PM EDT	Freeze Watch	PHI	Hunterdon, Morris, Somerset, Sussex, Warren	7 hr
Apr 21, 3:26 AM EDT	Freeze Warning	PHI	Hunterdon, Morris, Somerset, Sussex, Warren	30 hr
Apr 21, 12:25 PM EDT	Severe Thunderstorm Warning	PHI	Warren	50 min
Apr 21, 12:51 PM EDT	Severe Thunderstorm Warning	PHI	Sussex, Warren	21 min
Apr 21, 12:55 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Warren	27 min
Apr 21, 1:10 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden, Gloucester, Mercer, Salem	50 min
Apr 21, 1:17 PM EDT	Special Weather Statement	PHI	Hunterdon, Morris, Somerset, Sussex	58 min
Apr 21, 1:28 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Camden, Gloucester	36 min
Apr 21, 1:30 PM EDT	Special Marine Warning	PHI		60 min
Apr 21, 1:43 PM EDT	Severe Thunderstorm Warning	PHI	Hunterdon, Middlesex, Morris, Somerset	33 min
Apr 21, 1:58 PM EDT	Special Weather Statement	PHI	Burlington, Camden, Monmouth, Ocean	62 min
Apr 21, 2:02 PM EDT	Severe Thunderstorm Warning	PHI	Burlington, Camden, Monmouth, Ocean	43 min
Apr 21, 2:03 PM EDT	Special Weather Statement	PHI	Cumberland	27 min
Apr 21, 2:17 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Cumberland, Gloucester, Salem	43 min
Apr 21, 2:28 PM EDT	Special Weather Statement	PHI	Middlesex, Monmouth	47 min
Apr 21, 2:30 PM EDT	Special Marine Warning	PHI		60 min
Apr 21, 2:38 PM EDT	Severe Thunderstorm Warning	PHI	Monmouth, Ocean	37 min
Apr 21, 2:40 PM EDT	Special Marine Warning	PHI		55 min
Apr 21, 2:43 PM EDT	Special Weather Statement	PHI	Cape May	32 min
Apr 21, 2:50 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic, Burlington, Ocean	40 min
Apr 21, 3:02 PM EDT	Severe Thunderstorm Warning	PHI	Atlantic	28 min
Apr 21, 3:07 PM EDT	Special Marine Warning	PHI		53 min
Apr 21, 12:17 PM EDT	Severe Thunderstorm Warning	PHI	Berks, Bucks, Chester, Lehigh, Montgomery, Northampton	43 min
Apr 21, 12:54 PM EDT	Special Weather Statement	PHI	Delaware	36 min
Apr 21, 1:23 PM EDT	Severe Thunderstorm Warning	PHI	Kent	37 min
Apr 21, 2:09 PM EDT	Special Weather Statement	PHI	Sussex	36 min
Apr 21, 2:18 PM EDT	Severe Thunderstorm Warning	PHI	Kent, Sussex	42 min
Apr 21, 2:47 PM EDT	Severe Thunderstorm Warning	PHI	Sussex	16 min
Apr 21, 12:50 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Kent, Queen Anne's, Talbot	40 min

Nearby

Special Weather Statements in Pennsylvania, 2021 Every special weather statement 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.