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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 091231 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0731 AM CDT FRI AUG 09 2013 VALID 091300Z - 101200Z ...NO SVR TSTM AREAS FORECAST... ...SYNOPSIS... A CLOSED LOW OVER ONTARIO IS BEGINNING TO ACCELERATE TOWARD QUEBEC...IN RESPONSE TO UPSTREAM HEIGHT FALLS FROM THE WRN SHORE OF HUDSON BAY INTO NRN MANITOBA. A MID-UPPER SPEED MAX WILL LIKEWISE TRAVERSE THE GREAT LAKES AND NRN NEW ENGLAND ALONG THE SRN PERIPHERY OF THE CLOSED LOW. AN ASSOCIATED SURFACE COLD FRONT WILL PROGRESS SEWD ACROSS PA/NY AND THE OH VALLEY TODAY...REACHING SE NEW ENGLAND AND THE NRN MID ATLANTIC OVERNIGHT. MEANWHILE...A PERSISTENT CLOSED LOW INVOF THE NRN CA COAST WILL DRIFT ONLY SLOWLY NWD TOWARD SRN ORE...AS WEAK MIDLEVEL RIDGING CONTINUES OVER THE ROCKIES. ...SE NEW ENGLAND THROUGH THIS EVENING... A SWLY LLJ WILL DEVELOP EWD OVER SE NEW ENGLAND TODAY IN ASSOCIATION WITH A LEAD SPEED MAX EJECTING EWD FROM THE UPPER OH VALLEY...AND IN ADVANCE OF THE LARGER-SCALE LOW OVER ONTARIO. VERY MOIST PROFILES...WITH WIDESPREAD CLOUDS AND POOR LAPSE RATES...IS EXPECTED TODAY ACROSS SE NEW ENGLAND. THIS WILL LIMIT BUOYANCY...THOUGH ANY SUBSTANTIAL CLOUD BREAKS COULD BOOST SURFACE HEATING/INSTABILITY IN AN ENVIRONMENT WITH SUFFICIENT LOW-MIDLEVEL SHEAR AND HODOGRAPH CURVATURE FOR A LOW RISK OF STRONG GUSTS AND/OR A BRIEF/WEAK TORNADO. ...ERN OK TO WRN KY/TN THIS AFTERNOON... A CONVECTIVELY-ENHANCED MIDLEVEL TROUGH OVER NW OK THIS MORNING WILL DRIFT ENEWD TO THE SE KS/SW MO BORDER REGION BY TONIGHT. A WEAK COLD FRONT WILL SAG SWD FROM KY/MO TO TN/AR...MODIFIED BY ONGOING CONVECTION. WEAK CONVERGENCE ALONG THE FRONT...ALONG WITH DIFFERENTIAL HEATING ON THE SRN EDGE OF THE CLOUD BAND FROM ERN OK TO KY...WILL SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT THIS AFTERNOON AS THE MOIST BOUNDARY LAYER HEATS ALONG AND S OF THE EFFECTIVE FRONT. MODERATE INSTABILITY IS EXPECTED ALONG THE FRONT/DIFFERENTIAL HEATING ZONE...AND VERTICAL SHEAR WILL BE MORE FAVORABLE FOR ORGANIZED STORM CLUSTERS IN THE WEAK NELY FLOW ON THE IMMEDIATE COOL SIDE OF THE FRONT. A FEW DAMAGING GUSTS WILL BE POSSIBLE FROM ERN OK ACROSS NRN AR TO WRN TN...WHERE THE STRONGER INSTABILITY COINCIDES WITH A BELT OF SOMEWHAT ENHANCED MIDLEVEL FLOW ON THE IMMEDIATE SE SIDE OF THE WEAK MIDLEVEL TROUGH. ...NE NM AREA THROUGH EARLY TONIGHT... A DEPARTING MIDLEVEL TROUGH WILL LEAVE LITTLE LARGE-SCALE FOCUS FOR ASCENT ACROSS NE NM AND VICINITY. STILL...LINGERING LOW-LEVEL MOISTURE IN A WEAK UPSLOPE FLOW REGIME SHOULD SUPPORT AT LEAST WIDELY SCATTERED THUNDERSTORM DEVELOPMENT THIS AFTERNOON ALONG THE E SLOPES OF THE HIGHER TERRAIN. STORMS SHOULD SUBSEQUENTLY MOVE SLOWLY SEWD THROUGH THE EVENING...WITH SOME POTENTIAL FOR ISOLATED LARGE HAIL AND STRONG GUSTS GIVEN MLCAPE OF 1000-1500 J/KG AND EFFECTIVE BULK SHEAR OF 25-30 KT. ...SE MT/NE WY/SW SD TODAY... A WNW-ESE ORIENTED BAND OF CONVECTION IS WEAKENING THIS MORNING FROM SE MT TO SW SD. HOWEVER...THE BACKGROUND PATTERN OF WEAK LOW-LEVEL FRONTOGENESIS ALONG THIS SAME CORRIDOR WILL PERSIST... AND ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED THIS AFTERNOON. RESIDUAL LOW-LEVEL MOISTURE BENEATH THE NE EDGE OF THE STEEPER MIDLEVEL LAPSE RATES WILL CONTRIBUTE TO WEAK-MODERATE INSTABILITY...WHILE DEEP-LAYER VERTICAL SHEAR WILL BE AT LEAST MARGINALLY FAVORABLE FOR ORGANIZED MULTICELLS AND/OR SUPERCELLS. ISOLATED LARGE HAIL AND DAMAGING GUSTS WILL BE THE MAIN THREATS FOR A FEW HOURS THIS AFTERNOON/EVENING. ...NRN CA TO CENTRAL ORE THIS AFTERNOON/EVENING... SUFFICIENT LOW-MIDLEVEL MOISTURE AND ASCENT NE OF THE MIDLEVEL LOW WILL AGAIN PROMOTE THUNDERSTORM DEVELOPMENT THIS AFTERNOON FROM EXTREME N/NE CA INTO CENTRAL ORE. MODEST INSTABILITY AND DEEP-LAYER SELY SHEAR WILL SUPPORT A FEW ORGANIZED CLUSTERS CAPABLE OF PRODUCING ISOLATED STRONG/DAMAGING GUSTS AND MARGINALLY SEVERE HAIL. ..THOMPSON/ROGERS.. 08/09/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z |
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