Severe Thunderstorm Watch 427

Issued

Aug 11, 2021, 3:02 PM EDT (19:02 UTC)

Expired

Aug 11, 2021, 9:00 PM EDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

1 in

Strongest gust expected

50 kt

The State College radar (KCCX), 72 km from the middle of the area, began a volume at 19:02 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.

Two or more tornadoes

5%

One or more EF2 to EF5 tornadoes

2%

Ten or more severe wind reports

40%

One or more gusts of 65 knots or more

20%

Ten or more severe hail reports

20%

One or more hailstones of 2 inches or more

5%

Six or more combined severe hail and wind reports

60%

• Mesoscale Discussion 1477 Severe potential...watch possibleAug 11, 11:50 AM EDT
• Mesoscale Discussion 1481 Severe potential...watch possibleAug 11, 2:03 PM EDT
• Mesoscale Discussion 1490 Severe thunderstorm watch 427Aug 11, 6:44 PM EDT

234 
WWUS20 KWNS 111859
SEL7  
SPC WW 111859
DEZ000-MDZ000-NJZ000-PAZ000-CWZ000-120100-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 427
NWS Storm Prediction Center Norman OK
300 PM EDT Wed Aug 11 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northern Delaware
  Eastern Maryland
  Parts of western and southern New Jersey
  South central and southeastern Pennsylvania
  Coastal Waters

* Effective this Wednesday afternoon and evening from 300 PM
  until 900 PM EDT.

* Primary threats include...
  Scattered damaging wind gusts to 60 mph possible
  Isolated large hail events to 1 inch in diameter possible

SUMMARY...Scattered pulse-type severe storms are expected across
southern Pennsylvania and vicinity through the remainder of the
afternoon/evening, and new storms may also form along an outflow
boundary with ongoing storms approaching south central Pennsylvania.
Occasional wind damage with precipitation-loaded downbursts should
be the main severe threat, though isolated marginally severe hail
near 1 inch diameter may occur briefly in the strongest storms.

The severe thunderstorm watch area is approximately along and 55
statute miles north and south of a line from 20 miles northwest of
Altoona PA to 15 miles east southeast of Allentown PA. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU7).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 423...WW 424...WW
425...WW 426...

AVIATION...A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 50 knots. A few
cumulonimbi with maximum tops to 500. Mean storm motion vector
27015.

...Thompson

Severe Thunderstorm Watches in Pennsylvania, 2021Every severe thunderstorm watch in 2021

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.