Alert archive / Pennsylvania / Special Weather Statements in 2021

Special Weather Statement, NWS Philadelphia/Mount Holly

October 5, 2021Chester County, Pennsylvania

NWS Philadelphia/Mount Holly issued this special weather statement at Oct 5, 2021, 12:32 AM EDT for Chester County, Pennsylvania. It was in force for 43 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
Oct 5, 2021, 12:32 AM EDT (04:32 UTC)
Expired
Oct 5, 2021, 1:15 AM EDT
In force
43 min
Issued by
NWS Philadelphia/Mount Holly
Hail
0.00 in
Wind
40

County Chester County, PA

The radar

The Philadelphia radar (KDIX), 121 km from the middle of the area, began a volume at 04:32 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 00:00Z, 4.5 hours before the alert went out and 195 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 00:00Z on 2021-10-05Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1291 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 00:00Z on 2021-10-05The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 40 square meters per square second.193958Sfc1 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
1291 J/kg
Mixed-layer CIN
-7 J/kg
Mixed-layer LCL
1228 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
40 m²/s²
0-3 km storm-relative helicity
49 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.6

Open this sounding in Storm Lab

The text

As transmitted.

197 
WWUS81 KPHI 050432
SPSPHI

Special Weather Statement
National Weather Service Mount Holly NJ
1232 AM EDT Tue Oct 5 2021
 
PAZ060-101-103-050515-
Western Montgomery PA-Western Chester PA-Berks PA-
1232 AM EDT Tue Oct 5 2021

...A strong thunderstorm will impact portions of southeastern Berks,
northwestern Montgomery and northeastern Chester Counties through 115
AM EDT...

At 1232 AM EDT, Doppler radar was tracking a strong thunderstorm over
New Morgan, or 10 miles east of New Holland, moving northeast at 25
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...
Pottstown, Phoenixville, Birdsboro, Collegeville, Royersford, Trappe,
Honey Brook, Elverson, Bechtelsville, New Morgan, Pughtown,
Glenmoore, Chester Springs, Gilbertsville, Cedarville, Stowe,
Boyertown, Spring City, Pottsgrove and Lorane.

This includes the following highways...
 Pennsylvania Turnpike between mile markers 296 and 311.
 Interstate 176 in Pennsylvania between mile markers 1 and 8.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building. 

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 4043 7562 4016 7543 3999 7588 4007 7594
      4011 7594 4014 7588 4022 7601
TIME...MOT...LOC 0432Z 239DEG 20KT 4015 7590 

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

$$

PO

The office that day

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

IssuedProductOfficeCountiesLasted
Oct 5, 12:49 AM EDTSpecial Weather StatementPHISalem26 min
Oct 5, 2:10 AM EDTAreal Flood AdvisoryPHIBurlington, Camden, Gloucester, Salem4 hr
Oct 5, 2:27 AM EDTFlash Flood WarningPHICamden, Gloucester3 hr
Oct 5, 2:51 AM EDTSpecial Weather StatementPHIAtlantic39 min
Oct 5, 3:20 AM EDTAreal Flood AdvisoryPHIAtlantic, Burlington, Ocean3 hr
Oct 5, 3:33 AM EDTSpecial Weather StatementPHIAtlantic57 min
Oct 5, 1:24 AM EDTSpecial Weather StatementPHIMontgomery36 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.