SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0233 PM CDT MON APR 22 2013 VALID 222000Z - 231200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SRN KS AND PARTS OF OK... ...SRN KS/OK... EARLIER THOUGHTS REGARDING CONVECTION ACROSS SRN KS/OK REMAIN. HAVE MADE MINOR ADJUSTMENTS TO 10 PERCENT THUNDER LINE ACROSS NERN CO/NWRN KS AS COLD AIR DEEPENS ACROSS THIS REGION. ADDITIONALLY...STRONG HEATING ACROSS THE TX PANHANDLE HAS FORCED BOUNDARY LAYER FLOW TO VEER ACROSS THE ERN TX PANHANDLE. FOR THIS REASON HAVE NUDGED HIGHEST SEVERE PROBABILITIES EAST TOWARD THE OK BORDER. LATEST MODEL GUIDANCE CONTINUE TO SUGGEST TSTMS WILL INITIATE OVER SWRN KS/NWRN OK AFTER 22Z. IN THE ABSENCE OF SIGNIFICANT BOUNDARY LAYER CU NEAR THE DRYLINE/FRONTAL INTERSECTION THIS SEEMS REASONABLE. AFTER INITIATION THIS ACTIVITY SHOULD SPREAD/DEVELOP ESEWD DURING THE EVENING HOURS WITH AN ATTENDANT HAIL/WIND THREAT AS DEPICTED IN 1630Z OUTLOOK. ..DARROW.. 04/22/2013 .PREV DISCUSSION... /ISSUED 1111 AM CDT MON APR 22 2013/ ...SYNOPSIS... A BROAD...CYCLONIC FLOW REGIME WILL BE MAINTAINED ACROSS THE CONUS THROUGH THE D1 PERIOD. WITHIN THIS LARGE-SCALE PATTERN...A VORTICITY MAXIMUM OVER THE CNTRL HIGH PLAINS WILL PROGRESS THROUGH THE MID-MO VALLEY INTO UPPER MIDWEST IN ADVANCE OF A POSITIVELY TILTED SHORT-WAVE TROUGH WHICH WILL AMPLIFY FROM THE NRN PLAINS INTO GREAT BASIN. IN THE LOW LEVELS...THE WRN EXTENSION OF A COLD FRONT FROM THE UPPER GREAT LAKES SWWD THROUGH THE MID-MO VALLEY INTO CNTRL HIGH PLAINS WILL ACCELERATE SWD WITH THIS BOUNDARY EXTENDING FROM SWRN TX THROUGH THE OZARK PLATEAU INTO UPPER GREAT LAKES BY 23/12Z. A DRYLINE WILL MIX EWD ACROSS THE CNTRL/SRN HIGH PLAINS TODAY AND WILL EXTEND FROM IT/S INTERSECTION WITH THE COLD FRONT OVER SWRN KS SWD THROUGH THE FAR ERN TX PNHDL OR FAR WRN OK INTO W-CNTRL TX BY 23/00Z. ...SRN KS INTO OK AND TX/OK PNHDLS LATE THIS AFTERNOON INTO TONIGHT... A STRATUS RIBBON OBSERVED BY VISIBLE SATELLITE AND CURRENT GPS PW DATA SUGGEST A NARROW CORRIDOR OF HIGHER MOISTURE CONTENT /I.E. PW VALUES OF .80-.85 INCH AND BOUNDARY LAYER DEWPOINTS IN THE MID 50S/ BEING ADVECTED NWD THROUGH W-CNTRL TX INTO SWRN OK...BETWEEN SOUNDING SITES. THIS PROCESS WILL CONTINUE TODAY BENEATH AN EML WHERE 700-500-MB LAPSE RATES OF AROUND 8 C/KM WERE OBSERVED. WHEN COUPLED WITH DAYTIME HEATING...EXPECT THE WARM SECTOR AIR MASS TO BECOME MODERATELY UNSTABLE BY LATE AFTERNOON WITH MLCAPE APPROACHING 1000-1500 J/KG. ELEVATED TSTMS HAVE DEVELOPED THIS MORNING OVER N-CNTRL KS WITH THIS ACTIVITY LIKELY ROOTED WITHIN THE EML AND FORCED BY THE CNTRL PLAINS IMPULSE. ISOLATED OCCURRENCES OF HAIL APPROACHING SEVERE LEVELS WILL BE POSSIBLE WITH THESE STORMS OWING TO THE STEEP MIDLEVEL LAPSE RATES AND MODERATELY STRONG CLOUD-BEARING SHEAR. SUBSEQUENT...SURFACE-BASED STORM DEVELOPMENT IS EXPECTED TO BE DELAYED TO LATE THIS AFTERNOON OR EVENING OWING TO SUBSIDENCE IN THE WAKE OF THE LEAD IMPULSE AND AN INITIALLY CAPPED AIR MASS. THE MOST PROBABLE LOCATION FOR INITIATION IS ALONG THE COLD FRONT ACROSS SRN KS/NRN OK WHERE LOW-LEVEL CONVERGENCE IS MAXIMIZED. FORECAST HODOGRAPHS EXHIBIT A VERTICALLY VEERING WIND PROFILE WITH 50-60 KT OF EFFECTIVE BULK SHEAR WHICH WILL SUPPORT SUPERCELLS CAPABLE OF LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS. UPSCALE GROWTH OF STORMS INTO CLUSTERS OR AN MCS IS ANTICIPATED THIS EVENING INTO TONIGHT WITH A CONTINUED RISK FOR AT LEAST ISOLATED DAMAGING WINDS AND HAIL. ISOLATED...LATE DAY STORM DEVELOPMENT IS ALSO POSSIBLE SWD ALONG THE DRYLINE WITH A CONDITIONAL RISK FOR SUPERCELLS CAPABLE OF LARGE HAIL. HOWEVER...GIVEN THE STRONG CAP AND ABSENCE OF LARGE-SCALE FORCING FOR ASCENT...CONFIDENCE IN THIS SCENARIO REMAINS LOW.
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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