Alert archive / Pennsylvania / Special Weather Statements in 2021

Special Weather Statement, NWS Philadelphia/Mount Holly

August 10, 2021Chester County, Montgomery County, Philadelphia County, Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Aug 10, 2021, 5:11 PM EDT for Chester County, Montgomery County, Philadelphia County, Pennsylvania. It was in force for 34 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
Aug 10, 2021, 5:11 PM EDT (21:11 UTC)
Expired
Aug 10, 2021, 5:45 PM EDT
In force
34 min
Issued by
NWS Philadelphia/Mount Holly
Hail
0.25 in
Wind
40

Counties Chester County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 110 km from the middle of the area, began a volume at 21:13 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 nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.2 hours before the alert went out and 191 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 2021-08-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 529 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, Washington/Dulle, VA at 12:00Z on 2021-08-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 37 square meters per square second.1939Sfc1 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
529 J/kg
Mixed-layer CIN
-120 J/kg
Mixed-layer LCL
1096 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
37 m²/s²
0-3 km storm-relative helicity
65 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

429 
WWUS81 KPHI 102111
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
511 PM EDT Tue Aug 10 2021
 
PAZ070-071-101>104-102145-
Eastern Montgomery PA-Western Montgomery PA-Delaware PA-
Western Chester PA-Eastern Chester PA-Philadelphia PA-
511 PM EDT Tue Aug 10 2021

...Strong thunderstorms will impact portions of southern Montgomery,
Chester, central Philadelphia and central Delaware Counties through
545 PM EDT...

At 511 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Lansdale to near Honey Brook. Movement was
southeast at 20 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around 
         unsecured objects. Minor damage to outdoor objects is 
         possible.

Locations impacted include...
Philadelphia, West Chester, Norristown, Phoenixville, West Norriton,
East Norriton, Coatesville, Westtown, Downingtown, Conshohocken,
Ambler, Kennett Square, Collegeville, Royersford, Jenkintown,
Narberth, Trappe, Rockledge, Abington and Honey Brook.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 303 and 340.
 Northeast Extension between mile markers 21 and 30.
 Interstate 95 in Pennsylvania between mile markers 30 and 32.
 Interstate 76 in Pennsylvania between mile markers 327 and 342.
 Interstate 476 in Pennsylvania between mile markers 5 and 19.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building. 

&&

LAT...LON 4004 7593 4011 7594 4026 7536 4004 7498
      3981 7577 4003 7595
TIME...MOT...LOC 2111Z 313DEG 17KT 4021 7531 4007 7585 

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

$$

SFJ

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 10, 1:02 AM EDTSpecial Weather StatementPHIBurlington28 min
Aug 10, 3:33 AM EDTExcessive Heat WarningPHIBurlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 5 more4 days
Aug 10, 3:33 AM EDTHeat AdvisoryPHIAtlantic, Cape May, Cumberland, Monmouth, Ocean, Salem and 2 more4 days
Aug 10, 3:54 AM EDTAreal Flood AdvisoryPHIAtlantic80 min
Aug 10, 4:59 AM EDTAreal Flood AdvisoryPHIBurlington60 min
Aug 10, 5:58 AM EDTFlash Flood WarningPHIBurlington, Mercer2 hr
Aug 10, 2:07 PM EDTSpecial Weather StatementPHISalem38 min
Aug 10, 4:52 PM EDTSpecial Weather StatementPHIMonmouth23 min
Aug 10, 4:54 PM EDTSpecial Marine WarningPHI26 min
Aug 10, 5:05 PM EDTSpecial Weather StatementPHISomerset, Warren25 min
Aug 10, 5:09 PM EDTSevere Thunderstorm WarningPHIBurlington, Hunterdon, Mercer, Somerset, Warren51 min
Aug 10, 5:30 PM EDTSpecial Weather StatementPHIWarren30 min
Aug 10, 5:58 PM EDTSpecial Weather StatementPHIMercer, Middlesex, Morris, Somerset, Warren32 min
Aug 10, 6:27 PM EDTSpecial Weather StatementPHIBurlington, Mercer, Middlesex, Monmouth, Morris33 min
Aug 10, 6:59 PM EDTSpecial Weather StatementPHIMiddlesex, Monmouth31 min
Aug 10, 7:09 PM EDTSpecial Marine WarningPHI66 min
Aug 10, 7:27 PM EDTSpecial Weather StatementPHIMonmouth33 min
Aug 9, 10:10 PM EDTAreal Flood AdvisoryPHICarbon3 hr
Aug 10, 3:06 PM EDTSpecial Weather StatementPHIBerks24 min
Aug 10, 3:33 PM EDTSpecial Weather StatementPHIBerks27 min
Aug 10, 3:52 PM EDTSpecial Weather StatementPHIBerks, Carbon, Lehigh23 min
Aug 10, 4:01 PM EDTSevere Thunderstorm WarningPHIBerks, Carbon, Chester, Lehigh, Montgomery, Northampton44 min
Aug 10, 4:18 PM EDTAreal Flood AdvisoryPHIBerks, Carbon, Lehigh3 hr
Aug 10, 4:33 PM EDTSevere Thunderstorm WarningPHIBerks, Bucks, Carbon, Chester, Lehigh, Monroe and 2 more42 min
Aug 10, 5:40 PM EDTSpecial Weather StatementPHIChester35 min
Aug 10, 6:36 PM EDTSevere Thunderstorm WarningPHIBerks, Chester39 min
Aug 10, 7:10 PM EDTSevere Thunderstorm WarningPHIBerks, Chester, Montgomery65 min
Aug 10, 7:54 PM EDTSevere Thunderstorm Warning Considerable damage threatPHIChester51 min
Aug 10, 7:12 PM EDTSpecial Weather StatementPHIKent, Queen Anne's33 min
Aug 10, 7:42 PM EDTSpecial Weather StatementPHIKent, Queen Anne's, Talbot33 min

Nearby

Special Weather Statements in Pennsylvania, 2021Every 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.