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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 091217 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0717 AM CDT THU MAY 09 2013 VALID 091300Z - 101200Z ...THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO TONIGHT ACROSS MUCH OF THE SOUTHERN PLAINS INTO ADJACENT PORTIONS OF THE LOWER MISSISSIPPI VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE MIDDLE MISSISSIPPI INTO LOWER OHIO VALLEY... ...SYNOPSIS... UPPER TROUGHING APPEARS TO BE AMPLIFYING TO THE NORTHEAST OF A BLOCKING MID-LEVEL HIGH CENTER LINGERING OVER THE PACIFIC NORTHWEST. BUT A GENERALLY WEAK FLOW REGIME IS EXPECTED TO PERSIST ACROSS MUCH OF THE U.S...AS THE ASSOCIATED CYCLONIC BELT OF STRONGER WESTERLIES REMAINS NORTH OF THE INTERNATIONAL BORDER AREA THROUGH THIS PERIOD. THE PRIMARY EXCEPTION WILL REMAIN ACROSS THE SOUTHERN PLAINS...NEAR A STRONG ANTICYCLONIC HIGH-LEVEL JET WHICH HAS EMERGED FROM THE SUBTROPICAL EASTERN PACIFIC. THIS FEATURE MAY WEAKEN SOME TODAY...BUT A BELT OF MODERATELY STRONG CYCLONIC MID/UPPER FLOW CONTINUES TO DEVELOP EASTWARD ACROSS NORTHERN BAJA AND THE NORTHERN MEXICAN PLATEAU...AND IS FORECAST TO CONTINUE DEVELOPING EASTWARD ACROSS TEXAS...WITH SEVERAL EMBEDDED SPEED MAXIMA. WITHIN THE WEAK FLOW OVER THE MIDDLE OF THE COUNTRY...ONE WEAKENING CYCLONIC MID-LEVEL CIRCULATION IS EXPECTED TO SHIFT EAST OF THE MIDDLE MISSOURI VALLEY TOWARD THE SOUTHERN GREAT LAKES TODAY...WHILE ANOTHER CONTINUES TO SHIFT EAST OF THE CENTRAL ROCKIES. WITHIN WEST SOUTHWESTERLY FLOW TO THE SOUTHWEST OF THESE FEATURES...A COUPLE OF CONVECTIVELY GENERATED CYCLONIC VORTICITY MAXIMA ARE EXPECTED TO MIGRATE NORTHEASTWARD ACROSS THE MIDDLE MISSISSIPPI VALLEY...THROUGH THE LOWER OHIO VALLEY...TO THE NORTH OF THE OHIO RIVER. AT THE SAME TIME...A RETURN FLOW OFF THE WESTERN GULF OF MEXICO WILL CONTINUE TO STEADILY INCREASE MOISTURE ACROSS THE SOUTHERN PLAINS...LOWER HALF OF THE MISSISSIPPI VALLEY AND LOWER OHIO VALLEY. THIS WILL SUPPORT THE DEVELOPMENT OF CONSIDERABLE THUNDERSTORM ACTIVITY TODAY...AIDED BY DAYTIME HEATING. MEANWHILE...A RISK FOR THUNDERSTORMS WILL CONTINUE WITH A PERSISTENT MID-LEVEL CLOSED LOW...NOW CENTERED OVER THE NORTHERN MID ATLANTIC COAST STATES...AND FORECAST TO SHIFT ACROSS SOUTHERN NEW ENGLAND LATER TODAY/TONIGHT. AND THE ENVIRONMENT WILL REMAIN CONDUCIVE TO SCATTERED MOSTLY DIURNAL THUNDERSTORM DEVELOPMENT ACROSS PARTS OF THE ROCKIES...MUCH OF THE INTERMOUNTAIN WEST...AND THE SOUTHERN CASCADES INTO THE SIERRA NEVADA. ...SOUTHERN PLAINS... POTENTIAL CONVECTIVE EVOLUTION REMAINS UNCERTAIN TODAY ALONG AND SOUTH OF A WEAK FRONTAL ZONAL EXTENDING FROM THE MID/LOWER MISSOURI VALLEY INTO THE SOUTHERN HIGH PLAINS. BUT MODELS HAVE SIGNALED THAT LARGE-SCALE FORCING ASSOCIATED WITH AT LEAST ONE SPEED MAXIMUM MIGRATING NORTHEAST OF THE NORTHERN MEXICAN PLATEAU MAY CONTRIBUTE TO A DEVELOPING CLUSTER OF STORMS ACROSS CENTRAL TEXAS BY MIDDAY. THIS APPEARS SUPPORTED BY RECENT NEW STORM DEVELOPMENT EAST OF SAN ANGELO. GIVEN THE STEEP MID-LEVEL LAPSE RATES PRESENT ACROSS THE REGION...AND AT LEAST MODEST SHEAR...SEVERE HAIL MAY BE A THREAT WITH STRONGER CELLS AS THEY SPREAD EASTWARD AND CONVECTION INCREASES IN COVERAGE THIS MORNING. AS THE BOUNDARY LAYER ACROSS CENTRAL INTO EASTERN TEXAS CONTINUES TO MOISTEN AND WARM...SUBSTANTIVE INTENSIFICATION APPEARS POSSIBLE THIS AFTERNOON. AIDED BY INCREASING VERTICAL SHEAR ASSOCIATED WITH STRENGTHENING MID-LEVEL FLOW...ONE OR MORE ORGANIZED STORM CLUSTERS COULD EVOLVE WITH A RISK FOR STRONG WIND GUSTS...IN ADDITION TO SEVERE HAIL. OTHERWISE...SEVERE STORM POTENTIAL SEEMS MOST CERTAIN ALONG THE DRYLINE...FROM PARTS OF THE EDWARDS PLATEAU NORTHWARD INTO ITS INTERSECTION WITH THE COLD FRONT OVER SOUTHWEST OKLAHOMA OR NORTHWEST TEXAS DURING THE PEAK HEATING AFTERNOON HEATING. THERMODYNAMIC PROFILES CHARACTERIZED BY RATHER STEEP LOW THROUGH MID-LEVEL LAPSE RATES AND LARGE CAPE ARE EXPECTED TO BE SUPPORTIVE OF SUPERCELLS...SOME OF WHICH MAY PRODUCE VERY LARGE HAIL. CONVECTIVE POTENTIAL REMAINS MORE UNCLEAR ALONG THE FRONT ACROSS NORTHERN OKLAHOMA INTO WESTERN MISSOURI...AS CONVECTIVE OUTFLOW ASSOCIATED WITH A WEAKENING MESOSCALE CONVECTIVE SYSTEM APPEARS TO BE STABILIZING A SIGNIFICANT PORTION OF CENTRAL AND EASTERN OKLAHOMA INTO THE OZARKS. ...MIDDLE MISSISSIPPI/LOWER OHIO VALLEY... A BELT OF MODEST WEST SOUTHWESTERLY LOWER/MID TROPOSPHERIC FLOW...ON THE ORDER OF 30+ KT...ASSOCIATED WITH REMNANT CONVECTIVELY GENERATED CYCLONIC VORTEXES...MAY ENHANCE THUNDERSTORM ACTIVITY DEVELOPING ACROSS EAST CENTRAL MISSOURI INTO PARTS OF CENTRAL ILLINOIS AND NORTHERN/CENTRAL INDIANA BY THIS AFTERNOON. DESTABILIZATION TO THE SOUTH OF THE WEAK COLD FRONT...EXTENDING EAST NORTHEAST OF THE MID MISSOURI VALLEY INTO THE LOWER GREAT LAKES...MAY BE LIMITED BY RELATIVELY WEAK MID-LEVEL LAPSE RATES...PERHAPS WEAK SURFACE HEATING AS WELL. BUT IT COULD BECOME SUFFICIENT TO SUPPORT A RISK FOR SEVERE WIND GUSTS AND SOME HAIL IN STRONGER ACTIVITY...BEFORE CONVECTION WEAKENS THIS EVENING. ..KERR/ROGERS.. 05/09/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z |