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| Probabilistic Tornado Graphic | |||||||||
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| Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
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| Probabilistic Damaging Wind Graphic | |||||||||
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| Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. |
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| Probabilistic Large Hail Graphic | |||||||||
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| Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
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SPC AC 180559 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1259 AM CDT TUE JUN 18 2013 VALID 181200Z - 191200Z ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EARLY EVENING FOR SRN PARTS OF IL/IND/OH AND FAR NRN KY... ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON THROUGH TONIGHT ACROSS SRN AND CENTRAL HIGH PLAINS INTO CENTRAL PARTS OF SD/NEB... ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING ACROSS PARTS OF CENTRAL ID INTO NWRN AND NORTH CENTRAL MT... ...SYNOPSIS... THE NERN PACIFIC CLOSED LOW AND ATTENDANT TROUGH WILL ADVANCE EWD INTO THE WRN STATES THIS FORECAST PERIOD TAKING ON A NEGATIVE TILT...WITH THE LOW CENTERED ALONG THE WA/ORE COASTS AND THE TROUGH EXTENDING SEWD THROUGH NV BY 12Z WED. AN UPPER RIDGE CURRENTLY CENTERED OVER THE ROCKIES WILL SUBSEQUENTLY SHIFT EWD INTO THE PLAINS. A WEAK IMPULSE IS FORECAST TO TRACK EWD THROUGH THE RIDGE CROSSING THE CENTRAL ROCKIES AND REACHING THE CENTRAL PLAINS BY 12Z WED. MIDLEVEL FLOW IN THE NERN STATES WILL WEAKEN TODAY AS AN ATTENDANT SHORTWAVE TROUGH MOVES EWD FROM QUEBEC TO THE CANADIAN MARITIMES. A PROMINENT SHORTWAVE TROUGH...CURRENTLY TRACKING SEWD THROUGH THE ERN DAKOTAS PER WATER VAPOR IMAGERY...WILL MOVE INTO THE LOWER OH VALLEY REGION DURING PEAK HEATING...WHILE A LOWER TN VALLEY TROUGH SHIFTS EWD TO THE MID ATLANTIC STATES. AT THE SURFACE...A COLD FRONT WILL MOVE SWD THROUGH THE OH VALLEY...AND SEWD THROUGH NY/PA AND SRN NEW ENGLAND. MEANWHILE...A COLD FRONT ATTENDANT TO THE WRN U.S. TROUGH IS EXPECTED TO MOVE INTO THE NRN INTERMOUNTAIN WEST THIS AFTERNOON AND REACH WRN MT TONIGHT. ...OH VALLEY TO MID ATLANTIC STATES AND SRN NEW ENGLAND... THE COMBINATION OF SURFACE HEATING ACROSS THE OH VALLEY TODAY... SURFACE DEW POINTS AROUND 60 F AND MIDLEVEL LAPSE RATES OF 6.5 TO 7 C/KM ACCOMPANYING THE ERN DAKOTAS SHORTWAVE TROUGH SHOULD RESULT IN A MODERATELY UNSTABLE AIR MASS FROM IL TO OH. ALTHOUGH LOW LEVEL CONVERGENCE MAY NOT BE TOO STRONG ALONG THE SWD MOVING FRONT... FORCING FOR ASCENT ATTENDANT TO THE PROGRESSIVE TROUGH IS EXPECTED TO SUPPORT TSTM DEVELOPMENT. MLCAPE TO AT LEAST 1000 J/KG AND EFFECTIVE BULK SHEAR OF 35-40 KT PARALLEL TO THE FRONT SUGGEST LINE SEGMENTS SHOULD BE THE PRIMARY STORM MODE...THOUGH A FEW SUPERCELLS WILL BE POSSIBLE. DAMAGING WINDS AND HAIL WILL BE THE PRIMARY THREATS...WITH ACTIVITY DIMINISHING IN INTENSITY DURING THE EVENING AS THE BOUNDARY LAYER STABILIZES. FARTHER EAST ACROSS PA TO SRN NEW ENGLAND...TSTMS WILL BE POSSIBLE THROUGH THE AFTERNOON WITH A FEW ORGANIZED STORMS GIVEN 35-40 KT OF EFFECTIVE BULK SHEAR. HOWEVER...WEAKER INSTABILITY SHOULD LIMIT THE OVERALL SEVERE WEATHER THREAT...AND PRECLUDES HIGHER PROBABILITIES AND THE EWD EXTENSION OF THE SLIGHT RISK. FORCING FOR ASCENT ATTENDANT TO THE LOWER TN VALLEY TROUGH WILL SPREAD ACROSS VA/MD THIS AFTERNOON/EARLY EVENING...AND SHOULD SUPPORT SOME TSTM DEVELOPMENT. MODEL DIFFERENCES IN THE DEGREE OF DESTABILIZATION PRECLUDES THE ISSUANCE OF A CATEGORICAL SLIGHT RISK...THOUGH 30-40 KT WLY MIDLEVEL WINDS ACCOMPANYING THE TROUGH COULD PROMOTE SOME STORM ORGANIZATION. THUS...THIS OUTLOOK WILL EXTEND LOW SEVERE WIND/HAIL PROBABILITIES SWD ACROSS MD/VA. ...CENTRAL AND SRN HIGH PLAINS TO CENTRAL SD/NEB... SELY LOW LEVEL WINDS ARE EXPECTED TO STRENGTHEN TO 20-25 KT ACROSS THE FULL EXTENT OF THE HIGH PLAINS. TSTM DEVELOPMENT IS EXPECTED WITHIN THIS UPSLOPE FLOW REGIME FROM ERN NM TO ERN WY BY MID-LATE AFTERNOON WHERE THE AIR MASS WILL BE MODERATELY UNSTABLE. EFFECTIVE BULK SHEAR UP TO 35-40 KT WILL SUPPORT ORGANIZED STORMS WITH SUPERCELLS POSSIBLE RESULTING IN THREATS FOR HAIL AND DAMAGING WINDS. A NON-ZERO TORNADO THREAT IS FORECAST ACROSS MAINLY THE CENTRAL HIGH PLAINS...WHERE MODELS SUGGEST AN INCREASE IN LOW LEVEL SHEAR DURING THE EARLY EVENING. THERE IS SOME CONFIDENCE FOR AN MCS TO DEVELOP THIS EVENING INTO THE PART OF THE OVERNIGHT PERIOD ACROSS THE WRN HALF OF NEB/SD AS LOW LEVEL WAA INCREASES ALONG THE NOSE OF A STRENGTHENING/VEERING LLJ. DAMAGING WINDS AND HAIL WILL BE THE PRIMARY THREATS WITH THE MCS. ...PART OF CENTRAL ID/WRN AND NORTH CENTRAL MT... SURFACE DEW POINTS IN THE MID-UPPER 40S TO LOWER 50S COMBINED WITH SURFACE HEATING AND STEEP LAPSE RATES WILL RESULT IN MLCAPE OF AT LEAST 1000 J/KG ACROSS THE SLIGHT RISK AREA THIS AFTERNOON INTO THE EVENING. HEIGHT FALLS SPREADING EWD INTO THIS REGION IN THE AFTERNOON/EVENING WILL SUPPORT TSTM DEVELOPMENT WITH THE THREAT FOR HAIL AND DAMAGING WINDS...AS INCREASING BULK SHEAR SUPPORTS STORM ORGANIZATION INCLUDING A FEW SUPERCELLS. ..PETERS/ROGERS.. 06/18/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z |