

223 

WWUS20 KWNS 291956

SEL0

SPC WW 291956

MTZ000-NEZ000-SDZ000-WYZ000-300300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 700

NWS STORM PREDICTION CENTER NORMAN OK

155 PM MDT FRI JUL 29 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       WESTERN NEBRASKA PANHANDLE

       WESTERN SOUTH DAKOTA

       EASTERN WYOMING



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 155 PM UNTIL 900

PM MDT.



HAIL TO 2.5 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 65

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES SOUTH

SOUTHEAST OF SCOTTSBLUFF NEBRASKA TO 15 MILES NORTH NORTHWEST OF

BAKER MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 699...



DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND

INTENSITY THIS AFTERNOON ALONG LEE TROUGH AS REGION IS INFLUENCED BY

WEAK MIDLEVEL IMPULSE MOVING ACROSS WY.  THE PRESENCE OF A STEEP

MIDLEVEL LAPSE RATE ENVIRONMENT ATOP UPPER 50S TO LOW/MID 60S

BOUNDARY LAYER DEWPOINTS IS YIELDING A MODERATE AMOUNT OF AFTERNOON

INSTABILITY WITH MLCAPE VALUES OF 1000-2500 J/KG.  IN ADDITION...THE

ENTRANCE REGION OF AN UPPER-LEVEL JET STREAK OVER WY INTO SD/NEB IS

RESULTING IN 40-50 KT SHEAR THROUGH THE 0-6 AND 0-8-KM LAYERS WHICH

IS MORE THAN SUFFICIENT TO SUPPORT SUPERCELLS CAPABLE OF LARGE HAIL

AND DAMAGING WIND GUSTS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 25015.





...MEAD



422 

WWUS20 KWNS 291956

SEL0

SPC WW 291956

MTZ000-NEZ000-SDZ000-WYZ000-300300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 700

NWS STORM PREDICTION CENTER NORMAN OK

155 PM MDT FRI JUL 29 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST MONTANA

       WESTERN NEBRASKA PANHANDLE

       WESTERN SOUTH DAKOTA

       EASTERN WYOMING



EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 155 PM UNTIL 900

PM MDT.



HAIL TO 2.5 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 65

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES SOUTH

SOUTHEAST OF SCOTTSBLUFF NEBRASKA TO 15 MILES NORTH NORTHWEST OF

BAKER MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 699...



DISCUSSION...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND

INTENSITY THIS AFTERNOON ALONG LEE TROUGH AS REGION IS INFLUENCED BY

WEAK MIDLEVEL IMPULSE MOVING ACROSS WY.  THE PRESENCE OF A STEEP

MIDLEVEL LAPSE RATE ENVIRONMENT ATOP UPPER 50S TO LOW/MID 60S

BOUNDARY LAYER DEWPOINTS IS YIELDING A MODERATE AMOUNT OF AFTERNOON

INSTABILITY WITH MLCAPE VALUES OF 1000-2500 J/KG.  IN ADDITION...THE

ENTRANCE REGION OF AN UPPER-LEVEL JET STREAK OVER WY INTO SD/NEB IS

RESULTING IN 40-50 KT SHEAR THROUGH THE 0-6 AND 0-8-KM LAYERS WHICH

IS MORE THAN SUFFICIENT TO SUPPORT SUPERCELLS CAPABLE OF LARGE HAIL

AND DAMAGING WIND GUSTS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 25015.





...MEAD

