DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1241 AM CDT TUE JUL 09 2013 VALID 091200Z - 101200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY/WRN GREAT LAKES SWWD INTO THE CNTRL PLAINS... ...SYNOPSIS... AN UPPER-LEVEL SHORTWAVE TROUGH LOCATED OVER THE NRN HIGH PLAINS EARLY THIS MORNING WILL DIG SEWD AND AMPLIFY AS IT ENTERS THE UPPER MS VALLEY LATER THIS EVENING...AND THEN PROGRESSES EWD TOWARD THE GREAT LAKES REGION DURING THE OVERNIGHT. AHEAD OF THE UPPER TROUGH...AN EML WILL SPREAD FROM THE CNTRL HIGH PLAINS ACROSS A VERY MOIST BOUNDARY LAYER AIRMASS OVER THE MIDWESTERN STATES. AS A COLD FRONT ADVANCES SEWD FROM THE NRN PLAINS INTO THE MS VALLEY AND CNTRL PLAINS DURING THE AFTERNOON...SEVERE THUNDERSTORM DEVELOPMENT WILL BE LIKELY. ...UPPER MS VALLEY/WRN GREAT LAKES SWWD INTO THE CENTRAL PLAINS... MCS LOCATED OVER THE WRN/CNTRL DAKOTAS EARLY THIS MORNING IS FORECAST TO ENTER PORTIONS OF MN BY MID MORNING. OTHER STORMS OCCURRING WITHIN WAA REGIME TIED TO A 30 KT LLJ WERE SPREADING E ACROSS THE CNTRL PLAINS...AND WILL LIKELY MOVE INTO ERN IA BY MIDDAY. A MIDLEVEL IMPULSE COINCIDENT WITH THE IA CONVECTION WILL MOVE ESEWD INTO LOWER MI AND THE MID OH VALLEY BY AFTERNOON...AND MAY AID IN AN ISOLATED SEVERE THREAT AS THE BOUNDARY LAYER DESTABILIZES. BEHIND THE DEPARTING MORNING STORMS...SWLY WINDS AT 850 MB WILL AID IN ADVECTING A WARM EML AIRMASS NEWD TOWARD THE MS VALLEY. RICH MOISTURE WITH SURFACE DEWPOINTS IN THE 70S/PW VALUES LOCALLY NEAR 2.0 INCHES IS FORECAST TO BE PRESENT FROM ERN NEB INTO SRN MN AND WRN IL. GIVEN MORNING CLOUDS/CONVECTIVE DEBRIS CLEARS THE AREA...STRONG HEATING WILL YIELD MLCAPE VALUES NEAR 3000 J/KG OVER MUCH OF THE REGION. BY MID AFTERNOON...A COLD FRONT IS FORECAST TO BE LOCATED FROM NERN NEB INTO E-CNTRL MN. THIS FRONT WILL ACCELERATE SEWD DURING THE LATE AFTERNOON AND EVENING AS AN UPPER TROUGH DIGS FROM THE NRN PLAINS ACROSS THE UPPER MS VALLEY. FRONTAL FORCING COMBINED WITH THE VERY MOIST/UNSTABLE BOUNDARY LAYER WILL SUPPORT THE DEVELOPMENT OF THUNDERSTORMS. LOW-LEVEL SWLY FLOW WILL VEER TO WNWLY IN THE MIDLEVELS AS A 40-60 KT MIDLEVEL SPEED MAX SPREADS SEWD BEHIND THE FRONT. THIS WIND PROFILE COMBINED WITH THE VERY UNSTABLE ENVIRONMENT WILL FAVOR SUPERCELLS INITIALLY...WITH LARGE HAIL AND A COUPLE OF TORNADOES POSSIBLE. SEWD MOVING FRONT WILL LIKELY RESULT IN A QUICK TRANSITION TO A LINE WITH THE DOMINANT SEVERE THREAT EVOLVING TO DAMAGING WINDS. ...SERN AZ... STRONG SURFACE HEATING COMBINED WITH CLIMATOLOGICALLY HIGH PW VALUES NEAR 1.5 INCHES WILL AID IN MLCAPE VALUES APPROACHING 1000 J/KG OVER SERN AZ THIS AFTERNOON/EVENING. THIS WILL FAVOR THUNDERSTORM DEVELOPMENT OVER THE MOUNTAINOUS TERRAIN...WHICH MAY SPREAD WWD WITH TIME GIVEN THE PRESENCE OF LOW-LEVEL WLY FLOW SURMOUNTED BY 20 KT OF MIDLEVEL ELY FLOW. MARGINAL STORM ORGANIZATION IN THE FORM OF MULTICELL CLUSTERS AND SMALL LINES WILL BE POSSIBLE...AND MAY POSE AN ISOLATED THREAT FOR DAMAGING WINDS. ..GARNER/SMITH.. 07/09/2013
Posted on: Tue, 09 Jul 2013 06:36:17 +0000
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