Severe Thunderstorm Watch 577

Issued

Jun 30, 2011, 12:18 PM MDT (18:18 UTC)

Expired

Jun 30, 2011, 9:00 PM MDT

In force

9 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The Cheyenne radar (KCYS), 73 km from the middle of the area, began a volume at 18:18 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

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

40%

One or more gusts of 65 knots or more

40%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1449Jun 30, 11:57 AM MDT
• Mesoscale Discussion 1452Jun 30, 1:49 PM MDT
• Mesoscale Discussion 1455Jun 30, 4:17 PM MDT
• Mesoscale Discussion 1457Jun 30, 7:25 PM MDT

471 
WWUS20 KWNS 301818
SEL7
SPC WW 301818
COZ000-NEZ000-WYZ000-010300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 577
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM MDT THU JUN 30 2011

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

       CENTRAL AND NORTHEAST COLORADO
       WESTERN NEBRASKA PANHANDLE
       SOUTH-CENTRAL AND SOUTHEAST WYOMING

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1220 PM UNTIL
900 PM MDT.

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 120
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES SOUTH OF
CRAIG COLORADO TO 20 MILES NORTH NORTHEAST OF SIDNEY NEBRASKA.
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 576...

DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY ACROSS WATCH AREA THIS AFTERNOON AS INTENSIFYING
LARGE-SCALE FORCING FOR ASCENT AND VERTICAL SHEAR ATTENDANT TO UT
VORTICITY MAXIMUM OVERSPREAD A STEEP LAPSE RATE ENVIRONMENT.  THE
STRENGTHENING DEEP-LAYER WIND FIELD AND DEEP...WELL-MIXED PBL WILL
PROMOTE STRONG DOWNDRAFT DEVELOPMENT AS WELL AS HAIL WITH THE MOST
INTENSE STORMS.

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 22030.


...MEAD

Severe Thunderstorm Watches in Colorado, 2011Severe Thunderstorm Watches in Nebraska, 2011Severe Thunderstorm Watches in Wyoming, 2011Every severe thunderstorm 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.