Sep 5, 2012 2000 UTC Day 1 Convective Outlook
Updated: Wed Sep 5 19:52:32 UTC 2012
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20120905 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20120905 2000 UTC Day 1 Tornado Probabilities 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.
Probabilistic Damaging Wind Graphic
20120905 2000 UTC Day 1 Damaging Wind Probabilities 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.
Probabilistic Large Hail Graphic
20120905 2000 UTC Day 1 Large Hail Probabilities 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.
   SPC AC 051948
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0248 PM CDT WED SEP 05 2012
   
   VALID 052000Z - 061200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES TO THE
   NCNTRL GULF STATES...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS PARTS OF THE SRN PLAINS...
   
   EARLIER THOUGHTS REGARDING THE COMPLEX EVOLUTION OF
   AFTERNOON/EVENING CONVECTIVE PROCESSES REMAIN.  LATEST
   SATELLITE/RADAR IMAGERY DO SUPPORT THE CONTINUED SEWD PROPAGATION OF
   ONGOING MCS AS IT SPREADS ACROSS THE OH RIVER.  LEADING SQUALL LINE
   IS PROGRESSING SEWD AT ROUGHLY 25-30KT AND SUBSEQUENT MOVEMENT
   SHOULD RESULT IN TSTMS SPREADING ACROSS MUCH OF WRN/CNTRL KY BY 23Z.
   DAMAGING WINDS AND HAIL MAY ACCOMPANY THIS ACTIVITY.
   
   FARTHER WEST...A GENERAL UPWARD TREND IN BOTH BOUNDARY LAYER CU AND
   MID LEVEL CONVECTION ARE NOTED ACROSS SERN MO/NERN AR.  UPDRAFTS
   HAVE RECENTLY DEEPENED SUFFICIENTLY FOR LIGHTNING DISCHARGE AND
   FURTHER INTENSIFICATION IS EXPECTED.  THIS CONVECTION IS DEVELOPING
   ALONG LEADING EDGE OF OVERNIGHT/EARLY MORNING REMNANT MCS DEBRIS.
   
   MID LEVEL CONVECTION HAS STRUGGLED TO ATTAIN INTENSITY ALONG THE
   KS/OK BORDER EAST OF LBL.  HOWEVER...BOUNDARY LAYER IS DEEPENING
   ACROSS THE TX PANHANDLE PER RECENT CU EXPANSION AND WITH TIME IT
   APPEARS THE AGITATED REGION OVER NWRN OK SHOULD SEE UPWARD
   GROWTH/INTENSIFICATION.
   
   BOUNDARY LAYER CU FIELD IS EXPANDING IN AREAL COVERAGE WITHIN ZONE
   OF LOW LEVEL CONFLUENCE FROM ERN IA INTO SRN WI/NRN IL.  IT/S NOT
   ENTIRELY CLEAR HOW CONVECTION WILL EVOLVE ACROSS THIS REGION BUT
   CONTINUED HEATING WILL PROVE INSTRUMENTAL IN THUNDERSTORM
   DEVELOPMENT/INTENSIFICATION ACROSS THIS REGION LATER THIS AFTERNOON.
   
   ..DARROW.. 09/05/2012
   
   .PREV DISCUSSION... /ISSUED 1155 AM CDT WED SEP 05 2012/
   
   ...SYNOPSIS...
   BROAD...CYCLONIC FLOW WILL CONTINUE ACROSS THE NRN TIER THROUGH
   THU...WHILE FLAT RIDGE PERSISTS FROM THE FOUR CORNERS TO THE LWR MS
   VLY. ELSEWHERE...UPR VORT NOW NEAR MOBILE BAY /IN PART ASSOCIATED
   WITH FORMER TC ISAAC/ SHOULD SETTLE SLOWLY S INTO THE N CNTRL GULF
   WHILE UPR LOW OFF FLORIDA/S E CST CORRESPONDINGLY DUMBBELLS NWD.
   
   SEVERAL SHORTWAVE IMPULSES WILL MODULATE BOTH DAYTIME AND
   NOCTURNALLY ENHANCED TSTM DEVELOPMENT THROUGH THE PERIOD FROM PARTS
   OF THE SRN PLNS E/NE INTO THE OH VLY. SOME OF THESE STORMS WILL
   BECOME SVR AS THEY ORGANIZE INTO CLUSTERS LATER TODAY THROUGH EARLY
   THU.
   
   OTHER THAN PROGRESSIVE COLD FRONT OVER THE UPR MS VLY AND PLNS
   STATES...ASSOCIATED WITH MAIN UPR IMPULSE NOW ENTERING WI...FEATURES
   WILL REMAIN WEAK AT LWR LVLS...DOMINATED TO A LARGE EXTENT BY
   OUTFLOW FROM ON-GOING AND EARLIER CONVECTIVE COMPLEXES.
   
   ...GRT LKS/OH VLY/MID MS/LWR TN VLYS TODAY/TNGT...
   CONVECTIVE FCST WILL REMAIN COMPLEX OVER THIS BROAD REGION GIVEN /1/
   ON-GOING CONVECTION.../2/ LOW AMPLITUDE NATURE OF TWO-STREAM
   FLOW.../3/ AND WEAK SFC FEATURES.
   
   CONVECTIVE SYSTEM NOW OVER CNTRL IL SHOULD CONTINUE GENERALLY E OR
   ESEWD...SUPPORTED BY DIURNAL DESTABILIZATION AND GRADUAL ESE SPREAD
   OF STRENGTHENING MID LVL WNWLY FLOW/COOLING ON SRN EDGE OF WI UPR
   TROUGH. INCREASINGLY-FAVORABLE ENVIRONMENT FOR FORWARD PROPAGATION
   COULD EXTEND A RISK FOR SVR WIND...HAIL...AND POSSIBLY A TORNADO
   INTO PARTS OF OH...KY THROUGH THIS EVE.
   
   ADDITIONAL STORMS MAY FORM ON W SIDE OF THE IL COMPLEX THIS
   AFTN...SUPPORTED BY WAA ON ASSOCIATED COLD POOL...UPLIFT FROM
   RESIDUAL MCV NOW OVER CNTRL MO...AND PRESENCE OF DEEP EML/RICH
   LOW-LVL MOISTURE. ANY NEW CLUSTER EVOLVING FROM SUCH DEVELOPMENT
   SHOULD MOVE/PROPAGATE ESE TOWARD WRN KY/WRN TN...WITH AN ATTENDANT
   RISK FOR SVR WIND/HAIL.
   
   YET ANOTHER AREA OF POTENTIAL AFTN/EVE SVR STORM DEVELOPMENT WILL BE
   ALONG AND AHEAD OF COLD FRONT OVER PARTS OF WI/FAR ERN IA AND NW
   IL...AND OVER LWR MI. STRONG SFC HEATING...COUPLED WITH LOW LVL
   CONVERGENCE...STRENGTHENING DEEP SHEAR /WITH 500 MB WNW FLOW
   APPROACHING 50 KTS/...AND DEEP EML/RICH LOW-LVL MOISTURE WILL YIELD
   AN ENVIRONMENT FAVORABLE FOR SUPERCELLS IN THE WI/IL AREA. THESE MAY
   YIELD VERY LARGE HAIL AND HIGH WINDS.  TORNADOES ALSO WILL BE
   POSSIBLE...DEPENDING UPON STORM-SCALE INTERACTIONS AND MOVEMENT OF
   UPDRAFTS RELATIVE TO RESIDUAL OUTFLOW BOUNDARIES. THE STORMS SHOULD
   MERGE INTO ONE OR TWO LARGE MCS THAT COULD...FOR AT LEAST A FEW
   HOURS...CONTAIN APPRECIABLY-SIZED BOWING SEGMENTS WITH HIGH WIND.
   THIS ACTIVITY SHOULD GRADUALLY DIMINISH LATER TNGT/EARLY THU AS IT
   CONTINUE E/SE TOWARD/INTO THE LWR OH VLY AND ACROSS PARTS OF LWR MI.
   
   
   ...SRN PLNS THIS AFTN INTO TNGT...
   APPARENT DISTURBANCE CROSSING CO ATTM...IN SRN STREAM JET...IN
   CONJUNCTION WITH UPLIFT ALONG AFOREMENTIONED PLNS COLD FRONT...MAY
   FOSTER STRONG MID/LATE AFTN STORMS OVER THE TX PANHANDLE/WRN OK
   REGION. WITH AMPLE LOW-LVL MOISTURE /PW AOA 1 INCH/ AND STEEP  LOW
   TO MID-LVL LAPSE RATES TO SUPPORT STRONG UPDRAFTS...SOME OF THE
   STORMS COULD YIELD SVR WIND AND HAIL. AND...WITH SLY LLJ LIKELY TO
   STRENGTHEN OVER THE SRN HI PLNS THIS EVE IN RESPONSE TO CONTINUED
   MODERATE WLY FLOW ACROSS THE CNTRL/NRN RCKYS...THE STORMS MAY GROW
   INTO A SIZABLE CLUSTER OR TWO.  THESE SHOULD MOVE/DEVELOP GENERALLY
   SSEWD...EXTENDING A RISK FOR SVR WIND/HAIL PERHAPS AS FAR S AS THE
   TX S PLNS AND NW TX LATER TNGT.
   
   ...LONG ISLAND/MID ATLANTIC THIS AFTN...
   WEAK COLD FRONT TRAILING SE FROM SFC WAVE NOW MOVING OFF THE ME CST
   WILL CROSS THE MID ATLANTIC CST TOWARD PEAK HEATING...WHILE RELATED
   LEE TROUGH REMAINS MORE OR LESS STNRY FROM MD SSW INTO NC. THESE
   FEATURES WILL SERVE TO FOCUS DIURNALLY ENHANCED STORMS IN
   MOISTURE-RICH...WEAKLY-SHEARED ENVIRONMENT. FEW TSTMS/LINE SEGMENTS
   COULD YIELD STRONG/PERHAPS LOCALLY SVR WINDS.
   
   ...CNTRL GULF CST...
   NNW-SSE LWR TROPOSPHERIC AXIS OF CONFLUENCE ON THE NW SIDE OF NRN
   GULF OF MEXICO VORT COULD SUPPORT STRONG TO POSSIBLY SVR TSTMS WITH
   CONTINUED SFC HEATING LATER TODAY IN PARTS OF LA AND MS.  THE MAIN
   SVR THREAT WOULD BE LOCALLY DMGG WIND AND PERHAPS A TORNADO GIVEN
   HIGH PW AND MODERATE...DEEP UNIDIRECTIONAL NNWLY FLOW.
   
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