SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0105 AM CDT MON MAY 07 2012 VALID 071200Z - 081200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE OH/TN VALLEYS SWWD TO THE MID SOUTH AND ARKLATEX REGION... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WEST AND SOUTHWEST TX... ...SYNOPSIS... A CLOSED LOW...CURRENTLY MOVING EWD ACROSS SRN MANITOBA...AND ATTENDANT POSITIVELY TILTED TRAILING TROUGH WILL PROGRESS SEWD INTO THE NORTH CENTRAL STATES...WITH THE CLOSED LOW TRACKING INTO ONTARIO AND NRN MN. FARTHER W...A SHORTWAVE TROUGH...CURRENTLY MOVING SWD THROUGH SRN ID INTO NWRN UT...IS EXPECTED TO CLOSE OFF OVER LAS AS THIS FEATURE CONTINUES TO TRACK S...REACHING THE LOWER CO RIVER VALLEY BY 12Z TUE. THE EVOLUTION OF THE UPPER FLOW PATTERN WILL RESULT IN GENERALLY WEAK HEIGHT FALLS FROM THE OH/TN VALLEYS TO THE MID-SOUTH AND TX. A WEAK MIDLEVEL IMPULSE...CURRENTLY MOVING THROUGH CENTRAL KS/OK PER WATER VAPOR IMAGERY...IS FORECAST TO TRACK ENEWD FROM THE MID MS TO LOWER OH VALLEYS DURING THE FIRST HALF OF THE FORECAST PERIOD. THE TRAILING PORTION OF THIS TROUGH/VORTICITY LOBE WILL MOVE SEWD ACROSS AR BY LATE AFTERNOON. AT THE SURFACE...AN AREA OF LOW PRESSURE WILL TRACK FROM ERN IL TO NWRN OH BY 08/00Z...AND SHOULD REACH LAKE ERIE BY 12Z TUE. A COLD FRONT INITIALLY TRAILING SWWD FROM THE LOW THROUGH CENTRAL MO TO SOUTH CENTRAL OK...AND THROUGH CENTRAL TO SW TX WILL ADVANCE E/SEWD INTO THE OH/TN VALLEYS AND SEWD/SWD INTO THE MID-SOUTH AND MUCH OF TX 08/12Z. MEANWHILE...A WARM FRONT EXTENDING ESEWD FROM THE IL SURFACE LOW THROUGH CENTRAL IND/OH IS EXPECTED TO MOVE NNEWD TOWARD LAKE ERIE AND THE UPPER OH VALLEY. ...OH/TN VALLEYS TO MID-SOUTH AND ARKLATEX REGION... CONVECTION WITH EMBEDDED TSTMS MAY BE ONGOING AT 12Z TODAY FROM NERN OK THROUGH MO TO CENTRAL PARTS OF IL ALONG AND JUST AHEAD OF THE COLD FRONT. THERE MAY BE A FEW MORNING SHOWERS/TSTMS WITHIN THE WARM SECTOR...BUT SURFACE HEATING AHEAD OF THE COLD FRONT IS EXPECTED TO DECREASE INITIAL WEAK INHIBITION WITH CONVECTIVE TEMPERATURES IN THE UPPER 70S TO NEAR 80 F BEING REACHED BY LATE MORNING/EARLY AFTERNOON. THIS HEATING COMBINED WITH FURTHER MOISTENING OF THE PRE-FRONTAL AIR MASS /PW VALUES INCREASING TO 1.5 INCH THROUGH THE LOWER TN TO OH VALLEYS/ WILL SUPPORT THE DEVELOPMENT OF MODERATE INSTABILITY ACROSS THIS SLIGHT RISK AREA. THE STRONGEST INSTABILITY SHOULD RESIDE OVER THE SWRN EXTENT OF THE SLIGHT RISK AREA WHERE MOISTURE AND MIDLEVEL LAPSE RATES WILL BE GREATER. SCATTERED TO LOCALLY NUMEROUS TSTMS SHOULD DEVELOP BY AFTERNOON AND PERSIST INTO THE EARLY EVENING...ALONG/AHEAD OF SURFACE COLD FRONT AND NEAR/E OF SURFACE LOW. POCKET OF RELATIVELY ENHANCED LOW-LEVEL SHEAR IS LIKELY FROM THE SURFACE LOW ESEWD ALONG THE WARM FRONT... BENEATH SRN EXTENT OF FAVORABLE MIDLEVEL FLOW. THIS WILL SUPPORT A POTENTIAL FOR SUPERCELLS OVER PARTS OF OH AND PERHAPS WRN PA... DEPENDING ON EWD PROGRESS OF WARM FRONT. OTHERWISE...DEEP- LAYER WIND PROFILES AND VERTICAL SHEAR WILL BE WEAK...LEADING TO DOMINANT MULTICELL MODE IN LINES AND CLUSTERS. MAIN SEVERE WEATHER THREATS WILL BE DAMAGING DOWNDRAFT GUSTS AND SOME HAIL. THREAT SHOULD DECLINE MARKEDLY OVER MOST OF THE AREA AFTER DARK...THOUGH A FEW COLD-POOL DRIVEN CLUSTERS MAY PERSIST AFTER 06Z WITHIN THIS BROAD SLIGHT RISK AREA. ...SW/W TX... A COLD FRONT WILL MOVE INTO THE TX BIG BEND REGION THIS MORNING AND AFTERNOON AND SHOULD PROCEED FARTHER S INTO PART OF S CENTRAL TX TONIGHT. MEANWHILE...THE WRN EXTENT OF THIS BOUNDARY SHOULD BACK INTO THE HIGHER TERRAIN OF SW TX AND CENTRAL NM. MODELS SUGGEST THE COMBINATION OF STRONG SURFACE HEATING WITHIN A MOIST AIR MASS AND STEEP LAPSE RATES WILL SUPPORT TSTM DEVELOPMENT THIS AFTERNOON NEAR THE FRONT IN THE EDWARDS PLATEAU REGION AND EWD TO ERN TX AND WNWWD INTO THE MOUNTAINS OF SW TX AND NM. MODERATE TO STRONG INSTABILITY OVER THE TX HILL COUNTRY TO THE EDWARDS PLATEAU AND PECOS RIVER COMBINED WITH INCREASING BULK SHEAR SUGGEST ORGANIZED STORMS WILL BE POSSIBLE WITH HAIL AND STRONG WIND GUSTS THE PRIMARY THREATS. A CLUSTER OF TSTMS SHOULD PERSIST AFTER DARK INVOF THE TX BIG BEND REGION AS SELY LOW LEVEL WINDS STRENGTHEN RESULTING IN STRONG LOW LEVEL WAA. BULK SHEAR WILL REMAIN SUFFICIENT FOR ORGANIZED STORMS INTO THE EVENING/OVERNIGHT. ...SERN CONUS... SCATTERED MULTICELL TSTMS IN CLUSTERS ARE EXPECTED TO DEVELOP DURING THE AFTERNOON OVER AL/WRN GA TO NRN FL INCLUDING THE PANHANDLE... WITH OUTFLOW AND SEA BREEZE BOUNDARIES ACTING AS ADDITIONAL MESOSCALE FOCI. SURFACE HEATING AND DEW POINTS IN THE MID-60S TO LOW-70S F WILL CONTRIBUTE TO MLCAPE OF 1000-1500 J/KG. WEAK DEEP-LAYER WINDS WILL LIMIT OVERALL ORGANIZATION OF THIS ACTIVITY...HOWEVER ISOLATED DAMAGING GUSTS AND SVR HAIL ARE POSSIBLE. ..PETERS/HURLBUT.. 05/07/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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