Severe Thunderstorm Watch 491

Issued

Jul 18, 2012, 12:41 PM EDT (16:41 UTC)

Expired

Jul 18, 2012, 9:00 PM EDT

In force

8 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The Sterling radar (KLWX), 71 km from the middle of the area, began a volume at 16:42 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

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1489Jul 18, 10:25 AM EDT
• Mesoscale Discussion 1493Jul 18, 3:44 PM EDT

990 
WWUS20 KWNS 181642
SEL1
SPC WW 181642
DCZ000-DEZ000-MDZ000-NJZ000-NYZ000-PAZ000-VAZ000-WVZ000-CWZ000-19010
0-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 491
NWS STORM PREDICTION CENTER NORMAN OK
1245 PM EDT WED JUL 18 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       DISTRICT OF COLUMBIA
       DELAWARE
       MARYLAND
       NEW JERSEY
       SOUTHEAST NEW YORK
       CENTRAL AND EASTERN PENNSYLVANIA
       NORTHERN VIRGINIA
       EASTERN WEST VIRGINIA PANHANDLE
       COASTAL WATERS

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 1245 PM UNTIL
900 PM EDT.

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 80
STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES EAST OF
STAUNTON VIRGINIA TO 25 MILES EAST NORTHEAST OF WILKESBARRE
PENNSYLVANIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

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 490...

DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON AHEAD OF COLD FRONT AND LEE TROUGH.
AMBIENT WARM SECTOR IS HOT AND HUMID WITH MLCAPE VALUES OF
2000-3000+ J/KG.  WHEN COUPLED WITH STEEPENING LOW-LEVEL LAPSE RATES
AND HIGH PW VALUES...SETUP WILL FAVOR THE DEVELOPMENT OF INTENSE WET
MICROBURSTS CAPABLE OF DAMAGING WINDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 31020.


...MEAD

Severe Thunderstorm Watches in Pennsylvania, 2012Severe Thunderstorm Watches in Virginia, 2012Severe Thunderstorm Watches in Maryland, 2012Every severe thunderstorm watch in 2012

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.