SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1223 AM CDT SUN JUN 23 2013 VALID 231200Z - 241200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL HIGH PLAINS INTO THE UPPER MS VALLEY... ...SYNOPSIS... AN UPPER-LEVEL SHORTWAVE TROUGH AND ASSOCIATED 50+ KT MIDLEVEL WSWLY SPEED MAX WILL BE LOCATED OVER THE NRN PLAINS AT THE START OF THE FORECAST PERIOD...AND WILL THEN EJECT ENEWD INTO WRN ONTARIO BY 12Z MONDAY. W OF THIS FEATURE...SHORTWAVE RIDGING WILL OCCUR FROM THE SRN HIGH PLAINS INTO THE NRN ROCKIES...WHILE A SECOND UPPER TROUGH BECOMES POSITIONED FROM THE PAC NW INTO THE WRN GREAT BASIN. AT THE SURFACE...HIGH PRESSURE WILL BE CENTERED OFFSHORE FROM THE E COAST...WITH ANTICYCLONIC TRAJECTORIES LOCATED FROM THE GULF OF MEXICO INTO THE NERN CONUS. FARTHER W...A SURFACE COLD FRONT ASSOCIATED WITH THE NRN PLAINS TROUGH WILL EXTEND SWD ACROSS THE DAKOTAS INTO NRN KS BY MID MORNING...WITH THE NRN SEGMENT OF THE FRONT ADVANCING EWD ACROSS THE UPPER MS VALLEY DURING THE AFTERNOON/NIGHT. MEANWHILE...THE SRN SEGMENT OF THE FRONT WILL BECOME QUASI-STATIONARY FROM ERN NEB INTO NRN/WRN KS AND ERN CO...WITH UPSLOPE ELY FLOW DEVELOPING N OF THE FRONT OVER THE CNTRL HIGH PLAINS. ...CNTRL HIGH PLAINS... ESELY WINDS/UPSLOPE FLOW IS FORECAST TO DEVELOP OVER WRN NEB/KS AND ERN CO LATER THIS AFTERNOON...WHICH WILL AID IN MAINTAINING SURFACE DEWPOINTS IN THE 40/50S /MEAN BOUNDARY LAYER MIXING RATIOS FROM 8-11 G PER KG/ OVER THE AREA. THIS MOISTURE COMBINED WITH AFTERNOON TEMPERATURES IN THE 80S AND VERY STEEP MIDLEVEL LAPSE RATES /AOA 8 C PER KM IN THE 700-500 MB LAYER/ WILL SUPPORT MLCAPE VALUES FROM 1000-2500 J/KG. INITIAL THUNDERSTORM DEVELOPMENT MAY OCCUR ALONG THE FRONT RANGE DURING EARLY AFTERNOON...BUT IS EXPECTED TO MOVE E OFF THE MOUNTAINS AS THE BOUNDARY LAYER DESTABILIZES OVER THE HIGH PLAINS. ESELY LOW-LEVEL WINDS SURMOUNTED BY 30 KT MIDLEVEL WSWLYS WILL YIELD SUFFICIENT SHEAR FOR SUPERCELLS...WHICH WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL GIVEN THE PRESENCE OF VERY STEEP LAPSE RATES...IN ADDITION TO DAMAGING WIND GUSTS AND A TORNADO OR TWO. UPSCALE GROWTH INTO AN MCS IS POSSIBLE DURING THE NIGHT AS ACTIVITY MERGES AND ADVANCES E ACROSS NRN KS/SRN NEB. ...MID MO VALLEY INTO THE UPPER MS VALLEY... AN MCS /POSSIBLY DECAYING/ WILL LIKELY BE ONGOING OVER PORTIONS OF THE MID MO AND UPPER MS VALLEYS AT THE START OF THE PERIOD. BY MIDDAY INTO THE AFTERNOON...THUNDERSTORM REDEVELOPMENT WILL BE POSSIBLE ALONG OUTFLOW BOUNDARIES ASSOCIATED WITH THE MORNING MCS...AS WELL AS A COLD FRONT THAT WILL EXTEND SWWD FROM NRN MN INTO ERN NEB AND NRN KS. SURFACE DEWPOINTS FROM THE MID 60S TO LOW 70S COMBINED WITH A WARMING BOUNDARY LAYER ALONG AND AHEAD OF THE BOUNDARIES WILL SUPPORT STRONG INSTABILITY WITH MLCAPE VALUES RANGING FROM 2000-3000 J/KG. WLY DEEP-LAYER WIND PROFILES WILL BE STRONG ACROSS MN...WI...AND IA...AND WILL FAVOR MULTICELL CLUSTERS/LINE SEGMENTS POSING A RISK FOR DAMAGING WINDS AND LARGE HAIL. FARTHER SW OVER ERN NEB AND NERN KS/NRN MO...MODEL GUIDANCE SHOWS DIFLUENT SURFACE WINDS WILL BE PRESENT OVER THE AREA AS THE FLOW E OF THE AREA VEERS IN RESPONSE TO THE EJECTING NRN STREAM DISTURBANCE...AND BECOMES ELY W OF THE AREA. THIS COULD HINDER STORM COVERAGE DURING THE AFTERNOON/EVENING...AND PRECLUDE A MORE ROBUST SEVERE WEATHER THREAT DESPITE FORECAST SOUNDINGS SHOWING THE PRESENCE OF A VERY FAVORABLE THERMODYNAMIC ENVIRONMENT. HOWEVER...CONDITIONAL SEVERE WIND/HAIL PROBABILITIES HAVE BEEN MAINTAINED ATTM...GIVEN MESOSCALE DETAILS HAVE YET TO BE RESOLVED. ...NEW ENGLAND/NERN STATES... SWLY LOW-LEVEL FLOW WILL ESTABLISH 60S DEWPOINTS ACROSS PORTIONS OF NEW ENGLAND/NERN STATES ON SUNDAY. THIS MOISTURE COMBINED WITH DAYTIME HEATING /SURFACE TEMPERATURES NEAR 80F/ WILL AID IN MLCAPE VALUES FROM 1000-2000 J/KG ACROSS NRN PA INTO WRN ME. ISOLATED TO SCATTERED THUNDERSTORMS ARE FORECAST TO DEVELOP IN THIS ENVIRONMENT DURING THE AFTERNOON. DEEP-LAYER WLY FLOW WILL SUPPORT MULTICELL CLUSTERS AND LINE SEGMENTS WITH AN ATTENDANT THREAT FOR ISOLATED LARGE HAIL AND DAMAGING WIND GUSTS. ...SRN HIGH PLAINS... SIMILAR TO THE PAST COUPLE OF DAYS...STRONG HEATING AND DEEP BOUNDARY LAYER MIXING WILL OCCUR ADJACENT TO A SURFACE DRYLINE POSITIONED FROM THE NRN TX PANHANDLE SWWD INTO FAR W TX. THIS DESTABILIZATION COMBINED WITH DEWPOINTS IN THE 50S WILL AID IN MLCAPE VALUES NEAR 1500 J/KG...AND WILL SUPPORT ISOLATED THUNDERSTORM DEVELOPMENT DURING THE AFTERNOON/EVENING. ISOLATED INSTANCES OF SEVERE HAIL AND STRONG/SEVERE GUSTS WILL BE POSSIBLE...BUT THE OVERALL THREAT WILL BE LIMITED BY LACK OF STRONGER CAPE/SHEAR AND WEAK MIDLEVEL RIDGING. ..GARNER/MOSIER.. 06/23/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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