Oct 6, 2013 1300 UTC Day 1 Convective Outlook | |||||||||
Updated: Sun Oct 6 12:45:48 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 061241 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0741 AM CDT SUN OCT 06 2013 VALID 061300Z - 071200Z ...NO SVR TSTM AREAS FORECAST... ...SYNOPSIS... MAIN UPPER-AIR CONTRIBUTOR TO THIS OUTLOOK WILL BE WELL-DEFINED CYCLONE...CENTER OF WHICH IS EVIDENT IN MOISTURE CHANNEL IMAGERY AND INTERPOLATED 12Z RAOB DATA OVER WRN IA. RELATED 500-MB LOW IS FCST TO MOVE ESEWD TO BETWEEN DBQ-MLI BY 00Z...THEN PIVOT EWD ACROSS NRN IL THROUGH EVENING/OVERNIGHT HOURS. CONSIDERABLE SPREAD IS EVIDENT IN BOTH OPERATIONAL AND SREF MODEL MEMBERS AFTER ABOUT 06Z...REGARDING WHETHER THIS LOW PROCEEDS EWD OVER NRN INDIANA OR EJECTS NEWD ACROSS LM AND LOWER MI BY 12Z. SUCH SHORT-TERM SPREAD IS UNUSUAL FOR A SYSTEM WITH SHARP DEFINITION AND ORGANIZATION EMBEDDED WITHIN DOMESTIC RAOB NETWORK...AND APPEARS TO BE RELATED TO DISCREPANCIES IN AMPLIFICATION OF INITIALLY SEPARATE BUT STRENGTHENING SHORTWAVE TROUGH OVER MB THAT WILL CROSS NRN ONT THROUGH PERIOD. AT SFC...11Z ANALYSIS SHOWED COLD FRONT EXTENDING FROM NRN LM SSEWD OVER PORTIONS NRN/CENTRAL INDIANA...THEN SSWWD OVER WRN PORTIONS KY/TN/MS TO W-CENTRAL COAST OF LA...THEN ARCHING SWWD ACROSS NWRN GULF TO LOWER RIO GRANDE VALLEY REGION OF DEEP S TX. BY AROUND 00Z...FRONT SHOULD REACH CENTRAL OH...ERN TN...AND CENTRAL/SWRN AL. BY END OF PERIOD...FRONT SHOULD EXTEND OVER WRN PORTIONS NY...VA...NC AND GA. ...LOWER GREAT LAKES TO TN VALLEY AND SRN APPALACHIANS... SCATTERED TO WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP EPISODICALLY THROUGHOUT PERIOD...BUT ESPECIALLY FROM LATE MORNING INTO EVENING...IN BROAD PREFRONTAL SWATH. AT LEAST MRGL SVR POTENTIAL...PRIMARILY FOR DAMAGING GUSTS...WILL AFFECT THIS CORRIDOR. ANY HAIL IS EXPECTED TO BE MRGL/LOW-END SVR IN SIZE. EARLIER NORTHERN 15%/CATEGORICAL WIND RISK HAS BEEN REDUCED DUE TO CONCERNS OVER ONGOING CLOUD/PRECIP AND EFFECTS ON DIURNAL DESTABILIZATION. STILL...AS YET-TO-DEVELOP MESOSCALE TRENDS MAY WARRANT...RELATIVELY CONCENTRATED/SMALL AREA OF ENHANCED SVR POTENTIAL MAY DEVELOP SOMEWHERE WITHIN REMAINING 5% SWATH TODAY...SO A PARTIAL-AREA UPGRADE IS NOT OUT OF THE QUESTION. 35-45 KT EFFECTIVE SHEAR MAGNITUDES ARE POSSIBLE FOR ANY CONVECTION THAT DEVELOPS ALONG OR JUST AHEAD OF COLD FRONT...BASED ON MODIFIED FCST SOUNDINGS AND PLANAR PROGS SHOWING STRONGER MID-UPPER LEVEL WINDS BARELY OVERLAPPING WARM SECTOR. THIS CONCEPTUAL MODEL IS PREDICATED ON WEAKENING AND/OR DECELERATION OF ONGOING CONVECTIVE/PRECIP BAND...SUCH THAT PREFRONTAL OUTFLOW/DIFFERENTIAL HEATING BOUNDARY DOES NOT STAY AHEAD OF THAT INCREASE IN FLOW ALOFT. THOUGH CHARACTERIZED BY PERSISTENT WEAKENING TREND...ONGOING PRECIP PLUME IS ORIENTED FARTHER E AND FARTHER AHEAD OF COLD FRONT WITH NWD EXTENT...CASTING CONSIDERABLE UNCERTAINTY ON AMOUNT OF DIABATIC HEATING AND RELATED DESTABILIZATION THAT WILL OCCUR OVER LOWER MI AND WESTERN/CENTRAL OH. FARTHER S...WINDS ALOFT GENERALLY WILL BE WEAKER...BUT STILL MRGL FOR MULTICELLULAR/QUASI-LINEAR SVR POTENTIAL AND JUXTAPOSED WITH MORE SUSTAINED SFC HEATING. POCKETS OF SUCH HEATING...WITH SFC DEW POINTS UPPER 60S TO NEAR 70 F...SHOULD OFFSET WEAK LAPSE RATES ALOFT ENOUGH FOR AROUND 300-800 J/KG MLCAPE. ...CENTRAL/SRN APPALACHIANS OVERNIGHT... SHORTWAVE TROUGH EXTENDING SWD FROM MID-UPPER LEVEL LOW WILL BECOME MORE NEGATIVELY TILTED OVERNIGHT. AS THIS OCCURS...MORE VIGOROUS LOW-LEVEL MASS/MOISTURE RESPONSE TO STRENGTHENING LARGE-SCALE ASCENT...ALONG WITH GREATER MID-UPPER LEVEL FLOW...COULD OVERLAP WARM SECTOR OVER PORTIONS CENTRAL/SRN APPALACHIANS. SOME ORGANIZATION AND NEWD ACCELERATION OF PREFRONTAL CONVECTIVE BAND ACROSS THIS AREA MAY OCCUR...BUT INTO AIR MASS WITH VERY LIMITED INSTABILITY. AS SUCH...UNCONDITIONAL WIND PROBABILITIES ARE KEPT MRGL FOR NOW...BUT EXTENDED SOMEWHAT EWD OVER HIGHER TERRAIN. ..EDWARDS/LEITMAN.. 10/06/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z |