

926 

WWUS20 KWNS 141943

SEL3

SPC WW 141943

IAZ000-MNZ000-NEZ000-SDZ000-150200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 583

NWS STORM PREDICTION CENTER NORMAN OK

240 PM CDT TUE JUL 14 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST AND CENTRAL MINNESOTA

       EXTREME NORTHEAST NEBRASKA

       EASTERN SOUTH DAKOTA



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 240 PM UNTIL

900 PM CDT.



HAIL TO 2 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 10 MILES NORTH

NORTHEAST OF ALEXANDRIA MINNESOTA TO 30 MILES SOUTHEAST OF

YANKTON SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE

THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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.



DISCUSSION...THUNDERSTORMS ARE DEVELOPING ALONG THE SURFACE COLD

FRONT AND A PRE-FRONTAL TROUGH ACROSS ERN SD...AND THIS ACTIVITY

WILL LIKELY INCREASE IN COVERAGE/INTENSITY THROUGH THE AFTERNOON

WHILE SPREADING EWD.  TIME SERIES OF LOCAL PROFILERS AND VWP/S SHOW

A TREND TOWARD WEAKENING LOW-LEVEL SHEAR IN THE AREA WHERE STORMS

ARE FORMING AND WILL MOVE OVER THE NEXT FEW HOURS.  THE STRONGER

LOW-LEVEL SHEAR IS LOCATED ALONG THE WARM FRONT IN CENTRAL

MN...WHERE CLOUDS AND COOL SURFACE TEMPERATURES HAVE LIMITED

INSTABILITY.  PRESENT INDICATIONS ARE THAT THE COLD FRONTAL STORMS

WILL BE THE PRIMARY CONCERN THROUGH THE AFTERNOON...WITH THE

POSSIBILITY OF DAMAGING WINDS AND LARGE HAIL WITH LINE SEGMENTS

AND/OR SPLITTING SUPERCELLS.



AVIATION...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 500. MEAN STORM

MOTION VECTOR 27035.





...THOMPSON

