Severe Thunderstorm Watch 564

Issued

Aug 5, 2012, 3:36 PM EDT (19:36 UTC)

Expired

Aug 5, 2012, 8:28 PM EDT

In force

5 hr

Issued by

the Storm Prediction Center

Largest hail expected

1 in

Strongest gust expected

60 kt

The Sterling radar (KLWX), 72 km from the middle of the area, began a volume at 19:37 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

30%

One or more gusts of 65 knots or more

10%

Ten or more severe hail reports

10%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1708Aug 5, 2:49 PM EDT
• Mesoscale Discussion 1713Aug 5, 6:38 PM EDT

048 
WWUS20 KWNS 051938
SEL4
SPC WW 051938
DCZ000-DEZ000-MDZ000-NJZ000-PAZ000-VAZ000-CWZ000-060100-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 564
NWS STORM PREDICTION CENTER NORMAN OK
340 PM EDT SUN AUG 5 2012

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

       DISTRICT OF COLUMBIA
       NORTHERN DELAWARE
       CENTRAL MARYLAND
       WESTERN NEW JERSEY
       SOUTHEAST PENNSYLVANIA
       NORTHERN VIRGINIA
       COASTAL WATERS

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 340 PM UNTIL 900
PM EDT.

HAIL TO 1 INCH 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 70
STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES SOUTH
SOUTHWEST OF WASHINGTON DISTRICT OF COLUM TO 20 MILES NORTH OF
ALLENTOWN PENNSYLVANIA.  FOR A COMPLETE DEPICTION OF THE WATCH
SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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 563...

DISCUSSION...CONVECTION FORMING OVER E EDGE OF THE HIGHER TERRAIN
FROM NRN VA INTO SE PA SHOULD CONTINUE TO SPREAD EWD THROUGH THE
AFTERNOON/EVENING.  MODERATE INSTABILITY IS PRESENT AHEAD OF THESE
STORMS...WHERE SURFACE TEMPERATURES HAVE WARMED INTO THE LOW 90S
WITH DEWPOINTS IN THE LOW 70S.  GIVEN THE COMBINATION OF MLCAPE OF
1500-2500 J/KG PER THE 18Z IAD SOUNDING...AND ROUGHLY 30 KT
LOW-MIDLEVEL SWLY FLOW...THE STRONGER STORMS COULD PRODUCE A FEW
DAMAGING OUTFLOW GUSTS THROUGH THIS EVENING.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.
A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION
VECTOR 26020.


...THOMPSON

Severe Thunderstorm Watches in Virginia, 2012Severe Thunderstorm Watches in Maryland, 2012Severe Thunderstorm Watches in New Jersey, 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.