Tornado Watch 240

Issued

Apr 27, 2011, 6:15 PM EDT (22:15 UTC)

Expired

Apr 28, 2011, 12:42 AM EDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Sterling radar (KLWX), 148 km from the middle of the area, began a volume at 22:18 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

40%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

40%

One or more hailstones of 2 inches or more

30%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 627Apr 27, 3:22 PM EDT
• Mesoscale Discussion 628Apr 27, 3:55 PM EDT
• Mesoscale Discussion 631Apr 27, 4:39 PM EDT
• Mesoscale Discussion 633Apr 27, 6:00 PM EDT
• Mesoscale Discussion 638Apr 27, 6:50 PM EDT
• Mesoscale Discussion 641Apr 27, 7:55 PM EDT
• Mesoscale Discussion 645Apr 27, 10:12 PM EDT
• Mesoscale Discussion 648Apr 28, 12:09 AM EDT
• Mesoscale Discussion 649Apr 28, 12:27 AM EDT
• Mesoscale Discussion 650Apr 28, 12:34 AM EDT

557 
WWUS20 KWNS 272213
SEL0
SPC WW 272213
DCZ000-MDZ000-NCZ000-VAZ000-WVZ000-CWZ000-280600-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 240
NWS STORM PREDICTION CENTER NORMAN OK
615 PM EDT WED APR 27 2011

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

       DISTRICT OF COLUMBIA
       MARYLAND
       NORTHERN NORTH CAROLINA
       CENTRAL AND EASTERN VIRGINIA
       EASTERN WEST VIRGINIA
       COASTAL WATERS

EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 615 PM
UNTIL 200 AM EDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 15 MILES NORTHEAST OF
MARTINSBURG WEST VIRGINIA TO 30 MILES WEST SOUTHWEST OF RALEIGH
NORTH CAROLINA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).

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.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 233. WATCH NUMBER 233 WILL NOT BE IN EFFECT AFTER
615 PM EDT. CONTINUE...WW 232...WW 234...WW 235...WW 236...WW
237...WW 238...WW 239...

DISCUSSION...TSTMS HAVE RAPIDLY INTENSIFIED THIS EVENING WITHIN A
MOIST AND MODERATELY UNSTABLE ENVIRONMENT WITH MLCAPE VALUES OF
1000-2000 J/KG.  DEEP-LAYER VERTICAL SHEAR IS ALREADY SUPPORTIVE OF
SUPERCELLS...AND LOW-LEVEL SHEAR IS FORECAST TO STRENGTHEN THROUGH
THE REMAINDER OF THE EVENING WITH EFFECTIVE SRH VALUES APPROACHING
250-300 M2/S2.  AS SUCH...THE POTENTIAL FOR TORNADOES WILL EXIST IN
ADDITION TO DAMAGING WINDS AND HAIL.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24035.


...MEAD

Tornado Watches in Virginia, 2011Tornado Watches in North Carolina, 2011Tornado Watches in Maryland, 2011Every tornado watch in 2011

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.