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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 231958 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0258 PM CDT MON SEP 23 2013 VALID 232000Z - 241200Z ...NO SVR TSTM AREAS FORECAST... ...CENTRAL NEB AREA THIS AFTERNOON... THE VERTICALLY-STACKED LOW OVER SW NEB WILL MOVE ENEWD THROUGH THIS EVENING. THOUGH LOW-LEVEL MOISTURE REMAINS LIMITED WITHIN THE WARM SECTOR...COOL MIDLEVEL TEMPERATURES AND SURFACE HEATING/STEEP LOW-LEVEL LAPSE RATES HAVE CONTRIBUTED TO WEAK BUOYANCY NEAR AND N OF THE SURFACE CYCLONE IN NEB. LOW-TOPPED CONVECTION NEAR AND N OF THE LOW...IN THE ZONE OF STEEPEST LOW-LEVEL LAPSE RATES AND STRONGEST VERTICAL VORTICITY...COULD PRODUCE ISOLATED FUNNEL CLOUDS AND/OR A BRIEF TORNADO BEFORE THE BOUNDARY LAYER STABILIZES THIS EVENING. OTHERWISE...WEAK ELEVATED CONVECTION WILL PERSIST FROM NE KS INTO ERN NEB IN THE ZONE OF ASCENT PRECEDING THE MIDLEVEL WAVE. RELATIVELY POOR LAPSE RATES AND VERY LIMITED BUOYANCY DO NOT APPEAR SUPPORTIVE OF DAMAGING GUSTS...DESPITE STRONG VERTICAL SHEAR AND STRONG SURFACE HEATING E OF THE CONVECTIVE BAND. FOR ADDITIONAL INFORMATION...SEE MESOSCALE DISCUSSION 1908. ...CENTRAL FL THIS AFTERNOON... WIDESPREAD CLOUDS/RAIN WILL TEND TO LIMIT THE PROSPECTS FOR ADDITIONAL DESTABILIZATION THROUGH THE AFTERNOON. GIVEN THE RATHER MODEST BUOYANCY AND WEAK WIND PROFILES...THE THREAT FOR SEVERE STORMS APPEARS TOO MARGINAL TO WARRANT THE INTRODUCTION OF ANY PROBABILITIES. ..THOMPSON.. 09/23/2013 .PREV DISCUSSION... /ISSUED 1110 AM CDT MON SEP 23 2013/ ...SYNOPSIS... ERN CO UPR LOW WILL CONTINUE E INTO CNTRL NEB/KS LATER TODAY...BEFORE DEVOLVING INTO AN OPEN TROUGH WRN IA/MO EARLY TUE AS DEEPER/LARGER LOW EDGES SLOWLY E ACROSS ME/NEW BRUNSWICK. SFC LOW WITH THE CO SYSTEM SHOULD TRACK E ALONG THE KS-NEB BORDER TODAY AS TRAILING COLD FRONT ADVANCES E INTO CNTRL KS/WRN OK...AND INVERTED TROUGH EXTENDING N OF THE LOW PROGRESSES E ACROSS CNTRL PORTIONS OF NEB AND THE DAKOTAS. ELSEWHERE...W-E FRONT EXPECTED TO REMAIN NEARLY STNRY ACROSS THE NRN GULF OF MEXICO/CNTRL FL. SPARSE MOISTURE IN THE PLNS...AND WEAK SHEAR IN THE SOUTHEAST WILL LIMIT SVR THREAT THIS PERIOD...ALTHOUGH BRIEFLY STRONG TO POSSIBLY SVR STORMS COULD OCCUR IN BOTH AREAS. ...CNTRL PLNS THIS AFTN/EARLY EVE... LOW TO MID-LVL FORCING FOR ASCENT SHOULD FOCUS OVER WRN/CNTRL PORTIONS OF THE KS-NEB BORDER NWD INTO CNTRL NEB TODAY...IMMEDIATELY AHEAD OF MAIN UPR VORT ASSOCIATED WITH CO UPR LOW...AND E-N OF ASSOCIATED SFC LOW. MOISTURE WILL BE LIMITED...WITH PW RANGING FROM ABOUT .75 INCH IN KS TO AROUND AN INCH IN NEB. LAPSE RATES...HOWEVER...WILL BE STEEP...ESPECIALLY IN ARC OF EXPECTED MAXIMUM SFC HEATING THAT SHOULD EXTEND FROM SRN PORTIONS OF THE NEB SAND HILLS SSE TO THE KS BORDER. HEATING AND LOW-LVL UPLIFT SHOULD PROMOTE DEVELOPMENT OF A BAND OF LOW-TOPPED CONVECTION/STORMS ALONG INVERTED TROUGH/COLD FRONT OVER W CNTRL NEB AND PERHAPS FAR NRN KS BY LATE AFTN...WHERE ADEQUATE /25-30 KT/ S TO SSWLY DEEP SHEAR WILL EXIST FOR SUSTAINED/ORGANIZED STORMS. SPARSE MOISTURE WILL STRONGLY LIMIT CAPE AND THE LIKELIHOOD FOR SVR HAIL OR WIND GUSTS. BUT STRONG STATIC INSTABILITY IN THE PRESENCE OF BACKED LOW-LVL FLOW N AND E OF THE SFC LOW MAY PROVE SUFFICIENT TO YIELD AN UPDRAFT OR TWO WITH FUNNEL CLOUDS AND/OR A BRIEF TORNADO UNTIL SUNSET. ...CNTRL FL THIS AFTN... VWP DATA INVOF STALLED FRONT OVER CNTRL FL SHOW A MODEST...VERTICALLY-VEERING WIND PROFILE...WITH 700 MB SPEEDS AROUND 20 KTS. VERY MOIST AIR WILL REMAIN PRESENT OVER THE REGION...WITH PW AOA 2.25 INCHES. EARLIER TODAY A COUPLE SMALL TSTMS ALONG THE FRONT DISPLAYED WEAK LOW-LVL ROTATION...PERHAPS REFLECTING SLIGHTLY-ENHANCED LOW-LVL DIRECTIONAL SHEAR NEAR THE BOUNDARY. SFC HEATING MAXIMIZED S OF THE FRONT WILL FURTHER DESTABILIZE THE REGION...WITH ADDITIONAL TSTM DEVELOPMENT EXPECTED. OTHER STORMS MAY FORM ALONG OUTFLOW BOUNDARIES MOVING NNE INTO W CNTRL FL FROM DISTURBED AREA OVER THE SERN GULF OF MEXICO. AN ADDITIONAL STORM OR TWO MAY EXHIBIT WEAK LOW-LVL ROTATION THIS AFTN...ESPECIALLY AS THEY ENCOUNTER THE FRONT OR INTERACT WITH OTHER SLOWLY-MOVING...WARM OUTFLOWS IN THE VICINITY. BUT WEAKNESS OF THE BACKGROUND SHEAR AND LIKELIHOOD FOR DESTRUCTIVE INTERFERENCE BETWEEN STORMS SUGGEST THAT ADDITION OF LOW PROBABILISTIC TORNADO CONTOURS IS NOT WARRANTED ATTM. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z |
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