Note:
The expiration time in the watch graphic is amended if the watch is
replaced, cancelled or extended.
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Watch Status Reports.
SEL7
URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 377
NWS STORM PREDICTION CENTER NORMAN OK
200 PM EDT THU JUN 11 2009
THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
DISTRICT OF COLUMBIA
MUCH OF CENTRAL MARYLAND
CENTRAL VIRGINIA
THE EXTREME ERN WEST VIRGINIA PANHANDLE
COASTAL WATERS
EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 200 PM UNTIL
800 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 60
STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES EAST
NORTHEAST OF MARTINSBURG WEST VIRGINIA TO 10 MILES SOUTH
SOUTHWEST OF SOUTH HILL VIRGINIA. FOR A COMPLETE DEPICTION OF
THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS
WOU7).
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 374...WW 375...WW 376...
DISCUSSION...THE REMNANT OUTFLOW WITH AN OVERNIGHT AND MORNING MCS
IS PROGRESSING EWD INTO WRN/CENTRAL VA AND MD ALONG WITH A BELT OF
40-50 KT MID LEVEL FLOW ACCOMPANYING AN ASSOCIATED MCV. GIVEN
SURFACE HEATING/DESTABILIZATION E OF THIS SYSTEM...ESPECIALLY ACROSS
CENTRAL/SRN VA...EXPECT CONVECTION TO INCREASE ALONG THE OUTFLOW
BOUNDARY WITH AN INCREASING THREAT FOR DAMAGING WINDS AND LARGE HAIL
THROUGH THE AFTERNOON.
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 27025.
...THOMPSON
Note:
The Aviation Watch (SAW) product is an approximation to the watch area.
The actual watch is depicted by the shaded areas.
SAW7
WW 377 SEVERE TSTM DC MD VA WV CW 111800Z - 120000Z
AXIS..60 STATUTE MILES EAST AND WEST OF LINE..
45ENE MRB/MARTINSBURG WV/ - 10SSW AVC/SOUTH HILL VA/
..AVIATION COORDS.. 50NM E/W /13NW EMI - 52NE RDU/
HAIL SURFACE AND ALOFT..1.5 INCHES. WIND GUSTS..60 KNOTS.
MAX TOPS TO 500. MEAN STORM MOTION VECTOR 27025.
LAT...LON 39637606 36547704 36547919 39637833
THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
FOR WOU7.
Watch 377 Status Report Message has not been issued yet.
Note:
Click for Complete Product Text.
Tornadoes
Probability of 2 or more tornadoes
|
Low (20%)
|
Probability of 1 or more strong (F2-F5) tornadoes
|
Low (5%)
|
Wind
Probability of 10 or more severe wind events
|
Mod (40%)
|
Probability of 1 or more wind events > 65 knots
|
Mod (30%)
|
Hail
Probability of 10 or more severe hail events
|
Mod (30%)
|
Probability
of 1 or
more hailstones > 2 inches
|
Low (20%)
|
Combined Severe Hail/Wind
Probability of 6 or more combined severe hail/wind events
|
High (70%)
|
For each watch, probabilities for particular events inside the watch
(listed above in each table) are determined by the issuing forecaster.
The "Low" category contains probability values ranging from less than 2%
to 20% (F2-F5 tornadoes), less than 5% to 20% (all other probabilities),
"Moderate" from 30% to 60%, and "High" from 70% to greater than 95%.
High values are bolded and lighter in color to provide awareness of
an increased threat for a particular event.
weather.gov 
