Severe Thunderstorm Watch 721

Issued

Aug 20, 2009, 2:41 PM EDT (18:41 UTC)

Expired

Aug 20, 2009, 9:32 PM EDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The Cleveland radar (KCLE), 107 km from the middle of the area, began a volume at 18:41 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

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

50%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

20%

One or more hailstones of 2 inches or more

10%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1936Aug 20, 11:42 AM EDT
• Mesoscale Discussion 1940Aug 20, 6:20 PM EDT

756 
WWUS20 KWNS 201844
SEL1  
SPC WW 201844
KYZ000-OHZ000-PAZ000-WVZ000-LEZ000-210200-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 721
NWS STORM PREDICTION CENTER NORMAN OK
245 PM EDT THU AUG 20 2009

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

       EXTREME NORTHEAST KENTUCKY
       CENTRAL AND EASTERN OHIO
       EXTREME NORTHWEST PENNSYLVANIA
       NORTHWEST WEST VIRGINIA
       LAKE ERIE

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 245 PM UNTIL
1000 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 90
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH
NORTHEAST OF CLEVELAND OHIO TO 55 MILES SOUTH SOUTHWEST OF ATHENS
OHIO.  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.

DISCUSSION...BROKEN BANDS OF THUNDERSTORMS ARE DEVELOPING IN
ASSOCIATION WITH A REMNANT OUTFLOW BOUNDARY ACROSS CENTRAL OH...AND
A SEPARATE CONFLUENCE BAND IN WRN OH.  CONTINUED SURFACE HEATING/
DESTABILIZATION WILL SUPPORT STORM INTENSIFICATION AND INCREASING
STORM COVERAGE THROUGH THE AFTERNOON.  THE ENVIRONMENT IS SUPPORTIVE
OF BOTH DISCRETE CELLS /SOME WITH SUPERCELL STRUCTURE/ AND SHORT
LINE SEGMENTS...WITH DAMAGING WINDS THE PRIMARY THREAT.  AN
ISOLATED/BRIEF TORNADO MAY ALSO OCCUR ACROSS CENTRAL OR NORTHERN OH
WITH ONE OF THE DISCRETE STORMS GIVEN MODERATE LOW-LEVEL SHEAR IN A
MOIST PROFILE.

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 24035.


...THOMPSON

Severe Thunderstorm Watches in Ohio, 2009Severe Thunderstorm Watches in West Virginia, 2009Severe Thunderstorm Watches in Kentucky, 2009Every severe thunderstorm watch in 2009

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.