Tornado Watch 447

Issued

Aug 18, 2021, 11:37 AM EDT (15:37 UTC)

Expired

Aug 18, 2021, 11:00 PM EDT

In force

11 hr

Issued by

the Storm Prediction Center

Largest hail expected

0.5 in

Strongest gust expected

60 kt

The State College radar (KCCX), 107 km from the middle of the area, began a volume at 15:41 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.

Two or more tornadoes

50%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

10%

Ten or more severe hail reports

5%

One or more hailstones of 2 inches or more

5%

Six or more combined severe hail and wind reports

40%

• Mesoscale Discussion 1550 Severe potential...watch possibleAug 18, 8:46 AM EDT
• Mesoscale Discussion 1551 Severe potential...tornado watch likelyAug 18, 10:58 AM EDT
• Mesoscale Discussion 1555 Tornado watch 447Aug 18, 3:29 PM EDT
• Mesoscale Discussion 1557 Tornado watch 447Aug 18, 4:57 PM EDT

877 
WWUS20 KWNS 181533
SEL7  
SPC WW 181533
DCZ000-MDZ000-PAZ000-VAZ000-WVZ000-CWZ000-190000-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 447
NWS Storm Prediction Center Norman OK
1130 AM EDT Wed Aug 18 2021

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  District Of Columbia
  Maryland
  central and eastern Pennsylvania
  northern Virginia
  northeast West Virginia
  Coastal Waters

* Effective this Wednesday morning and evening from 1130 AM until
  800 PM EDT.

* Primary threats include...
  A few tornadoes possible
  Isolated damaging wind gusts to 70 mph possible

SUMMARY...Thunderstorms are expected to increase in intensity across
a portion of the Middle Atlantic and Northeast U.S. this afternoon
in association with the remnants of tropical cyclone Fred. Some of
the showers and thunderstorms will become capable of producing a few
tornadoes and isolated damaging wind.

The tornado watch area is approximately along and 100 statute miles
east and west of a line from 20 miles north northeast of
Williamsport PA to 70 miles south southwest of Martinsburg WV. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU7).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and 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.

&&

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 0.5 inches. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean
storm motion vector 19035.

...Dial

Tornado Watches in Pennsylvania, 2021Tornado Watches in Virginia, 2021Tornado Watches in Maryland, 2021Every tornado 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.