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.
SEL0
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 660
NWS STORM PREDICTION CENTER NORMAN OK
525 PM MDT TUE SEP 14 2010
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
WESTERN AND NORTHERN NEBRASKA
SOUTHWEST AND SOUTH CENTRAL SOUTH DAKOTA
EFFECTIVE THIS TUESDAY AFTERNOON AND WEDNESDAY MORNING FROM 525
PM UNTIL 100 AM MDT.
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 80 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 90 MILES WEST NORTHWEST OF
MULLEN NEBRASKA TO 50 MILES NORTH NORTHEAST OF ONEILL NEBRASKA.
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.
DISCUSSION...SCTD AREAS OF TSTMS EXPECTED TO MOVE/DEVELOP ENE ACROSS
WW AREA THOUGH EARLY WED AS WAA AND UPR LVL DIVERGENCE INCREASE
DOWNSTREAM FROM ERN WY/NRN CO UPR IMPULSE. DEEP SHEAR AND
INSTABILITY SHOULD REMAIN FAVORABLE FOR SUPERCELLS THROUGH LATE
TONIGHT...WITH WITH MODERATE STRENGTHENING OF SLY LLJ CONTRIBUTING
TO ENHANCED LOW LVL SHEAR. INCREASING CIN AFTER SUNSET MAY RESULT
IN MOST STORMS BEING SLIGHTLY ELEVATED. BUT COMBINATION OF FAIRLY
RICH MOISTURE WITH INCREASING ASCENT AND LOW LVL SHEAR ALONG STALLED
FRONT ON THE NEB/SD BORDER SUGGESTS A NON-ZERO RISK FOR
TORNADOES...IN ADDITION TO SVR WIND/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
550. MEAN STORM MOTION VECTOR 26025.
...CORFIDI
Note:
The Aviation Watch (SAW) product is an approximation to the watch area.
The actual watch is depicted by the shaded areas.
SAW0
WW 660 TORNADO NE SD 142325Z - 150700Z
AXIS..80 STATUTE MILES NORTH AND SOUTH OF LINE..
90WNW MHN/MULLEN NE/ - 50NNE ONL/ONEILL NE/
..AVIATION COORDS.. 70NM N/S /52NE BFF - 44NNE ONL/
HAIL SURFACE AND ALOFT..2 INCHES. WIND GUSTS..60 KNOTS.
MAX TOPS TO 550. MEAN STORM MOTION VECTOR 26025.
LAT...LON 43680269 44299830 41979830 41380269
THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
FOR WOU0.
Watch 660 Status Report Message has not been issued yet.
Note:
Click for Complete Product Text.
Tornadoes
Probability of 2 or more tornadoes
|
Mod (30%)
|
Probability of 1 or more strong (F2-F5) tornadoes
|
Low (20%)
|
Wind
Probability of 10 or more severe wind events
|
Mod (40%)
|
Probability of 1 or more wind events > 65 knots
|
Low (20%)
|
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.