Sep 8, 2013 1630 UTC Day 1 Convective Outlook | |||||||||
Updated: Sun Sep 8 16:12:36 UTC 2013 ( | ) | |||||||||
Probabilistic to Categorical Outlook Conversion Table |
Categorical Graphic | |||||||||
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Probabilistic Tornado Graphic | |||||||||
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 | |||||||||
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 | |||||||||
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 081608 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1108 AM CDT SUN SEP 08 2013 VALID 081630Z - 091200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF MT/WY EWD INTO PORTIONS OF THE DAKOTAS... ...SYNOPSIS... AN UPPER HIGH CENTERED OVER THE CNTRL PLAINS WILL SHIFT EWD INTO THE OZARKS IN RESPONSE TO THE EWD PROGRESSION OF AN UPPER LOW FROM THE NRN INTERMOUNTAIN REGION INTO THE NRN HIGH PLAINS. THIS PATTERN EVOLUTION WILL RESULT IN STRENGTHENING LARGE-SCALE FORCING FOR ASCENT AND MID AND UPPER-LEVEL FLOW FROM THE NRN HIGH PLAINS TOWARD UPPER MS VALLEY. IN THE LOW LEVELS...A LEE CYCLONE OVER NWRN NEB WILL DEEPEN WHILE DEVELOPING INTO NERN SD BY 9/12Z. AN ASSOCIATED SURFACE FRONT CURRENTLY EXTENDING FROM THE LOW ESEWD THROUGH ERN NEB...SRN IA INTO THE OH VALLEY WILL LIFT NWD IN RESPONSE TO A STRENGTHENING LOW-LEVEL WAA REGIME DOWNSTREAM FROM THE MIGRATORY CYCLONE. MEANWHILE...A DEVELOPING PACIFIC FRONT FROM THE NRN ROCKIES INTO GREAT BASIN WILL ADVANCE EWD THROUGH WRN PARTS OF THE DAKOTAS AND NEB BY THE END OF THE FORECAST PERIOD. ...PARTS OF MT/WY INTO THE DAKOTAS THIS AFTERNOON INTO TONIGHT... 12Z SOUNDINGS AND SATELLITE-DERIVED PW IMAGERY SHOW THE CONTINUED PRESENCE OF A SEASONABLY MOIST AIR MASS INVOF OF STALLED SYNOPTIC FRONT WITH BOUNDARY LAYER DEWPOINTS IN THE 60S TO LOWER 70S AND PW VALUES OF 1.2-1.8 INCHES. DECREASING MORNING CLOUDINESS COUPLED WITH THIS HIGH MOISTURE CONTENT AND STEEP MIDLEVEL LAPSE RATES WILL YIELD A MODERATELY UNSTABLE ENVIRONMENT BY AFTERNOON WITH MLCAPE VALUES RANGING FROM 1000-1500 J/KG OVER MT TO AS HIGH AS 2000-3000 J/KG ACROSS SD. CONVECTIVE EVOLUTION WILL BE DICTATED TO SOME DEGREE BY THE AREAL COVERAGE AND EXTENT OF LINGERING CLOUDS. BUT IN GENERAL...IT APPEARS THAT HEATING ALONG THE ELEVATED TERRAIN OF MT...WY...AND WRN SD...ALONG WITH INCREASING CONVERGENCE INVOF THE SYNOPTIC LOW AND NWD-DEVELOPING WARM FRONT WILL BE THE PRIMARY FOCI FOR STRONG TO SEVERE TSTM DEVELOPMENT THIS AFTERNOON INTO EVENING. GIVEN THE PRESENCE OF A VERTICALLY VEERING WIND PROFILE AND STRENGTHENING MID TO UPPER-LEVEL FLOW --AND RESULTANT VERTICAL SHEAR-- INITIAL STORM MODE WILL LIKELY BE SUPERCELLULAR WITH A RISK FOR LARGE HAIL...DAMAGING WINDS...AND PERHAPS A BRIEF TORNADO. AGGREGATING STORM-SCALE COLD POOLS AND THE DEVELOPMENT OF A NOCTURNAL LOW-LEVEL WIND MAXIMUM --WHICH WILL BE STRONGER AND BROADER THAN PAST NIGHTS-- WILL SUPPORT UPSCALE GROWTH OF STORMS INTO ONE OR MORE MCSS WITH THE RISK FOR DAMAGING WINDS AND HAIL CONTINUING INTO TONIGHT...MAINLY ACROSS NRN SD/SRN ND. ...OZARKS THIS AFTERNOON INTO EARLY EVENING... WEAK LOW-LEVEL WAA IS EXPECTED TO PERSIST TODAY...ENHANCING INFLOW/ASCENT ALONG THE WRN FLANK OF NOCTURNAL MCS ONGOING ACROSS PARTS OF CNTRL MO. THIS SHOULD SUPPORT REGENERATIVE STORM DEVELOPMENT ON THE WRN END OF THE RESIDUAL MCS WHERE DAYTIME HEATING AND BOUNDARY LAYER DEWPOINTS OF 65-70 F WILL PROMOTE MLCAPE APPROACHING 1500-2500+ J/KG. VERTICAL SHEAR WILL REMAIN RATHER WEAK...LIMITING THE POTENTIAL FOR STORM ORGANIZATION. NONETHELESS...LOCALLY DAMAGING WIND GUSTS WILL BE POSSIBLE OWING TO THE DEGREE OF INSTABILITY AND HIGH PW ENVIRONMENT. ..MEAD/LEITMAN.. 09/08/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z |