SPC 1300Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0734 AM CDT WED MAY 30 2012 VALID 301300Z - 311200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT ACROSS PART OF SWRN KS...WRN/CNTRL OK... AND FAR NRN TX... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL HIGH PLAINS INTO THE OZARK PLATEAU AND SRN PLAINS... --POTENTIALLY SIGNIFICANT SEVERE WEATHER EPISODE ACROSS PARTS OF THE CNTRL/SRN PLAINS THIS AFTERNOON INTO TONIGHT-- ...SYNOPSIS... POLAR BRANCH SHORT-WAVE TROUGH OVER THE NRN HIGH PLAINS WILL PROGRESS SEWD AND PHASE WITH LOWER-LATITUDE IMPULSES EMERGING FROM THE CNTRL/SRN PLAINS TO SUPPORT BROADER-SCALE TROUGH AMPLIFICATION FROM THE UPPER MS VALLEY INTO OZARK PLATEAU AND SRN PLAINS BY 31/12Z. THIS UPPER-AIR PATTERN EVOLUTION WILL RESULT IN THE EWD DEVELOPMENT AND/OR RE-FORMATION OF A SURFACE LOW FROM NWRN TX INTO THE OZARKS BY LATE TONIGHT/EARLY THU. AS THIS OCCURS...A COLD FRONT MOVING SEWD THROUGH THE NRN/CNTRL PLAINS WILL MERGE WITH A STATIONARY FRONT SITUATED OVER SRN KS/NRN OK INTO THE OZARK PLATEAU WITH THE COMPOSITE BOUNDARY --LIKELY AIDED BY CONVECTIVE OUTFLOW-- SURGING SEWD INTO THE SRN PLAINS. ...CNTRL/SRN PLAINS... 12Z SURFACE OBSERVATIONS SHOW THAT A CONVECTIVE OUTFLOW ASSOCIATED WITH DECAYING MCS OVER N-CNTRL/NERN TX EXTENDS FROM NEAR LFK NWWD THROUGH ACT TO A SURFACE LOW N OF LBB. VAD DATA FROM FREDRICK OK AND OK MESONET OBSERVATIONS INDICATE THAT THIS BOUNDARY IS QUITE SHALLOW OVER SWRN OK/NWRN TX WHERE SURFACE WINDS HAVE ALREADY VEERED TO A SELY DIRECTION. AND WHILE DEWPOINTS HAVE DROPPED INTO THE UPPER 50S AT MANY LOCATIONS ACROSS THE WRN HALF OF OK...INCREASED BOUNDARY LAYER MIXING WILL LIKELY RESULT IN VALUES INCREASING INTO THE LOW/MID 60S LATER TODAY. AT THE SAME TIME...A PLUME OF VERY STEEP MIDLEVEL LAPSE RATES /I.E. 8.5-9.5 C PER KM/ WILL OVERSPREAD WARM SECTOR AND CONTRIBUTE TO A MODERATE-STRONGLY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE RANGING FROM 1000-1500 J/KG IN SWRN NEB TO AS HIGH AS 3000-4000 J/KG ACROSS PARTS OF WRN OK. CONSIDERABLE VARIABILITY EXISTS AMONGST MESOSCALE AND CONVECTION-ALLOWING MODEL GUIDANCE WITH REGARD TO SPECIFIC DETAILS OF CONVECTIVE EVOLUTION THIS AFTERNOON INTO EVENING. CURRENT THINKING IS THAT THE PREFERRED CORRIDOR FOR STORM INITIATION WILL BE ACROSS WRN PARTS OF KS/OK BY MID AFTERNOON WHERE LARGE-SCALE FORCING FOR ASCENT PROGRESSIVELY OVERSPREADS WRN/NWRN EXTENSION OF WARM SECTOR. FORECAST HODOGRAPHS INDICATE VERTICALLY VEERING WIND PROFILES /MOST NOTABLY ACROSS WRN KS/ WITH 45-55 KT OF EFFECTIVE BULK SHEAR WHICH WILL SUPPORT RAPID SUPERCELL EVOLUTION. VERY LARGE HAIL AND A FEW TORNADOES WILL BE POSSIBLE WITH THE INITIAL STORMS BEFORE ACTIVITY GROWS UPSCALE INTO ONE OR MORE FORWARD-PROPAGATING MCSS. LARGE-SCALE PATTERN IS ANALOGOUS TO PAST CNTRL/SRN PLAINS DERECHO EVENTS...AND A SIMILAR TYPE SCENARIO MAY UNFOLD THIS EVENING INTO TONIGHT WITH THE POTENTIAL FOR WIDESPREAD DAMAGING WINDS FROM PARTS OF SRN KS THROUGH WRN/CNTRL OK INTO NRN TX. ...SERN TX/LA TO THE CNTRL GULF COAST... OUTFLOW BOUNDARY ASSOCIATED WITH DECAYING N-CNTRL/NERN TX MCS WILL LIKE FOCUS RENEWED TSTM DEVELOPMENT THIS AFTERNOON WITHIN A MOIST AND MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF 1000-2000 J/KG. DEEP-LAYER FLOW FIELD WOULD SUPPORT THE SEWD MOTION OF TSTM CLUSTERS WITH A RISK FOR SOME HAIL AND DAMAGING WINDS SPREADING TOWARD THE CNTRL GULF COAST THROUGH THIS EVENING. ..MEAD/ROGERS.. 05/30/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1300.html
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