DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0258 PM CDT SAT JUL 21 2012 VALID 212000Z - 221200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS EAST TX/FAR WESTERN LA... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NC... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHERN PLAINS... ...NORTHERN HIGH PLAINS/UPPER MIDWEST... SEE MESOSCALE DISCUSSION 1530 REGARDING ANTICIPATED INITIAL SEVERE TSTM DEVELOPMENT ACROSS PORTIONS OF NORTHEAST WY/WESTERN SD. PRIOR FORECAST REASONING GENERALLY HOLDS WITH THE BRUNT OF DEEP CONVECTIVE DEVELOPMENT STILL ANTICIPATED ACROSS THE WESTERN DAKOTAS THROUGH LATE AFTERNOON/EARLY EVENING. HAVE EXPANDED THE CATEGORICAL SLIGHT RISK EASTWARD ACROSS CENTRAL SD TO ACCOUNT FOR A DEGREE OF MCS SUSTENANCE THIS EVENING WITH AID OF A MODESTLY INCREASING LOW LEVEL JET...IN ACCORDANCE WITH AN ASSORTMENT OF HIGH-RES CONVECTION ALLOWING GUIDANCE. OTHER ELEVATED/WARM ADVECTION-AIDED STORMS ARE EXPECTED TO DEVELOP LATE TONIGHT ACROSS SOUTHERN MN/NORTHERN IA NEAR/NORTH OF FRONTAL ZONE...WITH SOME HAIL/PERHAPS WIND REMAINING POSSIBLE ON A MORE ISOLATED BASIS. ...ELSEWHERE... LITTLE/IF ANY CHANGES...SEE PRIOR OUTLOOK DISCUSSION BELOW AND MESOSCALE DISCUSSIONS 1526...1527...1528...1529. ..GUYER.. 07/21/2012 .PREV DISCUSSION... /ISSUED 1130 AM CDT SAT JUL 21 2012/ A BROAD UPPER RIDGE IS PRESENT FROM THE CENTRAL ROCKIES AND PLAINS STATES INTO THE MS VALLEY...WHILE WEAK UPPER TROUGHING AFFECTS THE PACIFIC NORTHWEST AND EASTERN STATES. SUBTLE FORCING MECHANISMS WILL RESULT IN ONLY ISOLATED AREAS OF THREAT FOR ORGANIZED SEVERE STORMS TODAY. ...TX/LA... A LONG-LIVED CLUSTER OF THUNDERSTORMS IS SPREADING SOUTHWESTWARD ACROSS MS/LA. STRONG HEATING ON THE WESTERN FLANK OF THIS CONVECTION WILL RESULT IN STEEP LOW LEVEL LAPSE RATES AND MODERATE INSTABILITY OVER PARTS OF EAST TX AND WESTERN LA LATER TODAY. STORMS MAY INTENSIFY TO SEVERE LEVELS...AIDED BY 20-25 KNOT NORTHEASTERLY MID LEVEL WINDS. LOCALLY GUSTY/DAMAGING WINDS WILL BE THE MAIN THREAT. ...ND/SD... EASTERLY LOW LEVEL WINDS ACROSS THE WESTERN DAKOTAS WILL HELP MAINTAIN SURFACE DEWPOINTS IN THE UPPER 50S TO LOWER 60S...WHILE STRONG DAYTIME HEATING OCCURS. MOST MODEL SOLUTIONS SUGGEST SCATTERED LATE AFTERNOON THUNDERSTORM DEVELOPMENT OVER NORTHEAST WY/WESTERN SD...AND ALONG THE MT/ND BORDER. BOTH AREAS WILL HAVE SUFFICIENT DEEP LAYER VERTICAL SHEAR FOR ORGANIZED/SUPERCELL STORM STRUCTURES CAPABLE OF HAIL AND DAMAGING WINDS. RELATIVELY SLOW STORM MOTIONS AND WEAK FORCING IS EXPECTED TO LIMIT THE EASTWARD EXTENT OF THE SEVERE THREAT THIS EVENING. ...CENTRAL/EASTERN NC... A VERY MOIST AND MODERATELY UNSTABLE AIR MASS IS PRESENT TODAY OVER CENTRAL/EASTERN NC. DEWPOINTS IN THE MID 70S COUPLED WITH SUBSTANTIAL DAYTIME HEATING WILL YIELD AFTERNOON MLCAPE VALUES OF 1500-2000 J/KG...DESPITE RATHER WEAK MID LEVEL LAPSE RATES. MODELS ARE IN AGREEMENT THAT SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THIS REGION LATER THIS AFTERNOON...MOVING TOWARD THE COAST THROUGH THE EARLY EVENING. THE 12Z MHX SOUNDING SHOWED SUFFICIENT LOW/MID LEVEL WIND FIELDS TO WARRANT A CONCERN FOR MORE A MORE ORGANIZED CLUSTER OF STRONG/SEVERE STORMS. LOCALLY GUSTY/DAMAGING WINDS WILL BE THE MAIN THREAT. ...SOUTHERN AZ... EASTERLY STEERING FLOW ACROSS CENTRAL/SOUTHERN AZ WILL ONCE AGAIN POSE A RISK THAT CONVECTION THAT FORMS OVER SOUTHEAST AZ COULD PROPAGATE WESTWARD INTO THE LOWER DESERTS. SEVERAL SURFACE OBS ALONG THE AZ/MEXICAN BORDER BETWEEN YUM AND WEST OF TUS SHOW DEWPOINTS IN THE UPPER 60S...WHICH MAY INCREASE ODDS OF MAINTENANCE OF STORMS WELL INTO THE EVENING. ANY DEEP CONVECTION THAT OCCURS ACROSS THIS AREA WILL POSE A RISK OF LOCALLY DAMAGING WINDS. NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z CURRENT UTC TIME: 2012Z (3:12PM), RELOAD THIS PAGE TO UPDATE THE TIME
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