Alert archive / Pennsylvania / Special Weather Statements in 2021

Special Weather Statement, NWS Philadelphia/Mount Holly

August 23, 2021Montgomery County, Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Aug 23, 2021, 4:41 PM EDT for Montgomery 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 23, 2021, 4:41 PM EDT (20:41 UTC)
Expired
Aug 23, 2021, 5:15 PM EDT
In force
34 min
Issued by
NWS Philadelphia/Mount Holly
Hail
0.00 in
Wind
40

County Montgomery County, PA

The radar

The Philadelphia radar (KDIX), 102 km from the middle of the area, began a volume at 20:41 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, 8.7 hours before the alert went out and 207 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 2021-08-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 5 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 2021-08-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 90 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
5 J/kg
Mixed-layer CIN
-84 J/kg
Mixed-layer LCL
1259 m above ground
0-6 km bulk shear
22 kt
0-1 km storm-relative helicity
90 m²/s²
0-3 km storm-relative helicity
46 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

656 
WWUS81 KPHI 232041
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
441 PM EDT Mon Aug 23 2021
 
PAZ101>104-232115-
Eastern Montgomery PA-Western Montgomery PA-Western Chester PA-
Eastern Chester PA-
441 PM EDT Mon Aug 23 2021

...A strong thunderstorm will impact portions of southwestern
Montgomery and northeastern Chester Counties through 515 PM EDT...

At 441 PM EDT, Doppler radar was tracking a strong thunderstorm over
Royersford, or 17 miles north of West Chester, moving southeast at 15
mph.

HAZARD...Wind gusts up to 40 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around 
         unsecured objects.

Locations impacted include...
West Chester, Norristown, Pottstown, Phoenixville, West Norriton,
East Norriton, Collegeville, Royersford, Trappe, Pughtown, Valley
Forge, Paoli, Chester Springs, King Of Prussia, Cedarville, Plymouth
Meeting, Lionville-Marchwood, West Goshen, Stowe and Bridgeport.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 314 and 333.
 Interstate 76 in Pennsylvania between mile markers 327 and 329.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building. 

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4024 7570 4031 7558 4011 7529 3995 7559
TIME...MOT...LOC 2041Z 334DEG 14KT 4020 7555 

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

$$

Gorse

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 22, 8:11 PM EDTAreal Flood AdvisoryPHIWarren6 hr
Aug 22, 8:47 PM EDTFlash Flood WarningPHISussex, Warren6 hr
Aug 22, 11:27 PM EDTAreal Flood WarningPHIMiddlesex29 hr
Aug 23, 2:09 AM EDTRiver Flood WarningPHIMorris, Passaic17 hr
Aug 23, 3:25 AM EDTAreal Flood WarningPHIMorris8 hr
Aug 23, 4:10 AM EDTRiver Flood WarningPHIMorris41 hr
Aug 23, 5:07 AM EDTAreal Flood WarningPHIWarren21 hr
Aug 23, 5:22 AM EDTAreal Flood WarningPHISomerset9 hr
Aug 23, 5:44 AM EDTAreal Flood WarningPHIHunterdon7 hr
Aug 23, 7:20 AM EDTRiver Flood WarningPHIHunterdon, Somerset7 hr
Aug 23, 7:47 AM EDTRiver Flood WarningPHIMorris, Passaic13 hr
Aug 23, 8:36 AM EDTAreal Flood WarningPHISomerset9 hr
Aug 23, 8:42 AM EDTRiver Flood WarningPHIMiddlesex, Somerset21 hr
Aug 23, 11:22 AM EDTRiver Flood WarningPHIMiddlesex, Somerset16 hr
Aug 23, 11:32 AM EDTRiver Flood WarningPHIEssex, Morris, Passaic5 days
Aug 23, 11:58 AM EDTRiver Flood WarningPHISomerset15 hr
Aug 23, 12:19 PM EDTRiver Flood WarningPHIBurlington33 hr
Aug 23, 12:51 PM EDTCoastal Flood StatementPHIOcean3 hr
Aug 23, 2:26 PM EDTAreal Flood WarningPHISussex14 hr
Aug 23, 2:26 PM EDTSpecial Weather StatementPHIOcean49 min
Aug 23, 3:12 PM EDTSpecial Weather StatementPHIOcean33 min
Aug 23, 3:15 PM EDTSevere Thunderstorm WarningPHIOcean45 min
Aug 23, 3:18 PM EDTSpecial Marine WarningPHI57 min
Aug 23, 3:38 PM EDTRiver Flood WarningPHIEssex, Morris, Passaic48 hr
Aug 23, 4:47 PM EDTSpecial Weather StatementPHIAtlantic28 min
Aug 23, 4:50 PM EDTSpecial Marine WarningPHI55 min
Aug 23, 5:13 PM EDTSpecial Weather StatementPHICamden32 min
Aug 23, 5:39 PM EDTSpecial Marine WarningPHI33 min
Aug 23, 6:46 PM EDTSpecial Marine WarningPHI64 min
Aug 22, 10:34 PM EDTAreal Flood AdvisoryPHICarbon, Lehigh, Northampton3 hr
Aug 22, 10:53 PM EDTFlash Flood WarningPHICarbon, Lehigh, Monroe, Montgomery, Northampton4 hr
Aug 22, 11:42 PM EDTAreal Flood AdvisoryPHIBerks3 hr
Aug 23, 12:32 AM EDTRiver Flood WarningPHIMonroe10 hr
Aug 23, 12:55 AM EDTRiver Flood WarningPHIMonroe10 hr
Aug 23, 2:36 AM EDTAreal Flood WarningPHICarbon, Monroe21 hr
Aug 23, 3:50 AM EDTRiver Flood WarningPHICarbon3 hr
Aug 23, 3:50 AM EDTRiver Flood WarningPHILehigh, Northampton11 hr
Aug 23, 8:28 AM EDTAreal Flood WarningPHILehigh7 hr
Aug 23, 7:14 PM EDTSevere Thunderstorm WarningPHIKent, New Castle31 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.