Tornado Watch 154

Issued

Apr 21, 2007, 12:57 PM MDT (18:57 UTC)

Expired

Apr 21, 2007, 9:46 PM MDT

In force

9 hr

Issued by

the Storm Prediction Center

Largest hail expected

3 in

Strongest gust expected

60 kt

The North Platte radar (KLNX), 73 km from the middle of the area, began a volume at 18:58 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

80%

One or more EF2 to EF5 tornadoes

30%

Ten or more severe wind reports

70%

One or more gusts of 65 knots or more

30%

Ten or more severe hail reports

95%

One or more hailstones of 2 inches or more

50%

Six or more combined severe hail and wind reports

95%

• Mesoscale Discussion 524Apr 21, 12:35 PM MDT
• Mesoscale Discussion 527Apr 21, 4:57 PM MDT

000
WWUS20 KWNS 211904
SEL4  
SPC WW 211904
COZ000-NEZ000-220400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 154
NWS STORM PREDICTION CENTER NORMAN OK
200 PM CDT SAT APR 21 2007

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

       NORTHEAST COLORADO
       WESTERN AND CENTRAL NEBRASKA

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 200 PM UNTIL
1100 PM CDT.

TORNADOES...HAIL TO 3 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 85 STATUTE
MILES EAST AND WEST OF A LINE FROM 20 MILES EAST SOUTHEAST OF
IMPERIAL NEBRASKA TO 25 MILES EAST NORTHEAST OF VALENTINE
NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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...TSTMS EXPECTED TO DEVELOP IN WRN AND SRN PARTS OF WW
OVER THE NEXT 2 HOURS OR SO AS LOW LEVEL CONVERGENCE AND HEATING
CONTINUE ALONG FRONT/LEE TROUGH EXTENDING NE FROM SE CO LEE LOW. 
COUPLED WITH ARRIVAL OF INCREASED FORCING FOR ASCENT IN EXIT REGION
OF 80 KT NM MID LVL SPEED MAX...REGION WILL BE FAVORABLE FOR
LONG-LIVED SUPERCELLS.  DEGREE OF INSTABILITY...LOW LEVEL VEERING
PROFILES INVOF SW/NE FRONT...AND POTENTIAL FOR SOME STORMS TO MOVE
ALONG THE BOUNDARY SUGGEST A MODERATE PROBABILITY FOR TORNADOES IN
ADDITION TO LARGE HAIL AND POSSIBLY HIGH WIND.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 22035.


...CORFIDI

Tornado Watches in Nebraska, 2007Tornado Watches in Colorado, 2007Every tornado watch in 2007

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.