SPC AC 092011
DAY 1 CONVECTIVE OUTLOOK RESENT 1
NWS STORM PREDICTION CENTER NORMAN OK
0311 PM CDT WED JUN 09 2010
VALID 092000Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX THROUGH THE LOWER
MS VALLEY...TN VALLEY AND A PORTION OF KY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF ERN GA
THROUGH NWRN SC...
...ERN TX THROUGH THE LOWER MS VALLEY...
CLUSTERS OF STORMS CONTINUE DEVELOPING WITHIN ZONE OF DEEPER ASCENT
ASSOCIATED WITH SLOW MOVING UPPER LOW OVER SERN TX. LEADING STORMS
MOVING INTO NWRN LA/SWRN AR HAVE DEVELOPED INTO A BOW ECHO SYSTEM.
THE ATMOSPHERE REMAINS QUITE UNSTABLE DOWNSTREAM FROM THIS ACTIVITY
WITH 2000+ J/KG MLCAPE. CONVERGENCE ALONG LEADING GUST FRONT AND
WEAK CAP SHOULD MAINTAIN AT LEAST A LOOSELY ORGANIZED FORWARD
PROPAGATING MCS THROUGH NRN LA AND SRN AR. ISOLATED/SPORADIC STRONG
TO DAMAGING WIND APPEARS TO BE THE MAIN THREAT...THOUGH A COUPLE OF
BRIEF TORNADOES REMAIN POSSIBLE THIS AFTERNOON. SEVERE THREAT SHOULD
UNDERGO A GRADUAL DECREASE BY MID EVENING AS THE BOUNDARY LAYER
STABILIZES.
...CNTRL HIGH PLAINS...
THE ATMOSPHERE REMAINS CAPPED OVER THE CNTRL HIGH PLAINS THIS
AFTERNOON. STRONGEST DIABATIC WARMING IS OCCURRING OVER CO WITH MORE
LIMITED HEATING FARTHER NORTH ACROSS ERN WY DUE TO EXTENSIVE MID
LEVEL CLOUDS. PRIMARY MECHANISM FOR CONVECTIVE INITIATION WILL BE
OROGRAPHIC FORCING OVER THE HIGHER TERRAIN OF CNTRL AND NRN CO INTO
SERN WY. STORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON OVER THE
HIGHER TERRAIN THEN SPREAD EWD INTO THE HIGH PLAINS AS THE BOUNDARY
LAYER DESTABILIZES AND THE CAP WEAKENS. EFFECTIVE SHEAR FROM 40-45
KT WILL SUPPORT SUPERCELLS WITH LARGE HAIL THE MAIN THREAT...THOUGH
A COUPLE OF TORNADOES WILL ALSO BE POSSIBLE. STORMS COULD EVENTUALLY
EVOLVE INTO A FORWARD PROPAGATING MCS AS THEY CONTINUE EWD THROUGH
THE HIGH PLAINS THIS EVENING.
..DIAL.. 06/09/2010
.PREV DISCUSSION... /ISSUED 1128 AM CDT WED JUN 09 2010/
...LOWER TN/OH VALLEYS TO CENTRAL/SRN APPALACHIANS...
CLOUDS AND PCPN ARE EXPECTED TO LIMIT INSTABILITY ACROSS PORTIONS OF
SRN OH/WV AND...SO SEVERE WEATHER PROBABILITIES HAVE BEEN LOWERED IN
THESE AREAS. THE MAIN THREAT FOR SEVERE STORMS IN THIS REGION MAY BE
KY LATER TODAY AS UPPER TROUGH FROM ERN IL/CENTRAL MO SWEEPS EWD.
MORNING CLUSTER OF STORMS OVER WRN KY APPEARS TO BE ASSOCIATED WITH
UPPER TROUGH FORCING AND MORNING VISIBLE IMAGERY SUGGESTS SOME
HEATING/ DESTABILIZATION MAY OCCUR AHEAD OF THESE STORMS. THE MAIN
THREAT WOULD BE COULD BE EVENTUAL LINE SEGMENTS WITH THE POTENTIAL
FOR WIND DAMAGE. DESPITE STRONG SHEARED ENVIRONMENT EAST OF CENTRAL
APPALACHIANS...ONLY VERY LOW CONDITIONAL SEVERE PROBABILITIES ARE
DEPICTED...GIVEN INCREASING CLOUDS AND WEAK LAPSE RATES/INSTABILITY.
FURTHER SOUTH...THOUGH THE MID LEVEL FLOW IS A LITTLE WEAKER THAN IN
KY...A BAND OF CONVECTION STRETCHED FROM ERN TN SWWD INTO NRN AL.
THESE STORMS MAY INTENSIFY AS THEY MOVE INTO A WARMING/
DESTABILIZING AIR MASS WITH AROUND 20 KT OF MID LEVEL FLOW.
EFFECTIVE SHEAR NEAR 30 KT SHOULD BE SUFFICIENT FOR SEVERE MULTICELL
STORMS WITH WIND DAMAGE AND SOME HAIL.
...NRN LA/CENTRAL/NRN MS...
A SLIGHT RISK HAS BEEN ADDED FOR THIS AFTERNOON DUE TO VERY MOIST
BOUNDARY LAYER...DEWPOINTS IN THE 70S...ALREADY RESULTING IN STRONG
INSTABILITY...MLCAPES NEAR 2500 J/KG. ALSO...PRESENCE OF CENTRAL TX
UPPER LOW HAS RESULTED IN AROUND 25 KT OF MID LEVEL FLOW. THE SHEAR
SHOULD BE FAVORABLE FOR A FEW SEVERE MULTICELL CLUSTERS. THE DEGREE
OF INSTABILITY AND VERY MOIST BOUNDARY LAYER INDICATES THAT STRONG
DOWNBURSTS/WIND DAMAGE SHOULD BE THE PRIMARY THREAT.
...CENTRAL HIGH PLAINS...
SSELY LOW LEVEL FLOW HAD ALREADY MOISTENED THE BOUNDARY LAYER WITH
SURFACE DEWPOINTS IN THE 50S. CLOUDS ACROSS ERN CO WERE SHOWING
SIGNS OF THINNING...AND WITH HEATING...SBCAPES FROM 1500-2500 J/KG
ARE ANTICIPATED BY LATE AFTERNOON ACROSS THE WRN PORTIONS OF SLIGHT
RISK AREA. WHILE LARGE SCALE FORCING FOR ASCENT SHOULD BE
WEAK...MOIST UPSLOPE FLOW NEAR HIGHER TERRAIN SHOULD SUPPORT STORM
DEVELOPMENT BY LATE IN THE DAY. ONCE STORMS DEVELOP...STRONGLY
VEERING WINDS IN THE LOWER 1 TO 2 KM... COMBINED WITH SPEED SHEAR
BETWEEN 700-500 MB...SHOULD PROVIDE SUFFICIENT SHEAR FOR SUPERCELLS.
WHILE THE LOW LEVEL SHEAR WOULD SUPPORT A TORNADO OR
TWO...THERMODYNAMIC PROFILES INDICATE LARGE HAIL SHOULD BE THE
PRIMARY THREAT. AN EVOLUTION TO A SEWD MOVING MCS INTO NEB/NWRN KS
IS POSSIBLE TONIGHT AS LOW LEVEL JET INCREASES ACROSS THE HIGH
PLAINS.
...ERN/CENTRAL TX...
VERY HIGH PW VALUES...2+ INCHES...WILL PERSIST IN ERN QUADRANT OF
SLOW NEWD MOVING CENTRAL TX UPPER LOW. AREA VWP DATA SHOW ENHANCED
SLY LOW TO MID LEVEL FLOW ON EAST SIDE OF SYSTEM...WITH SLIGHTLY
BACKED WINDS AT THE SURFACE. STRONG/SEVERE STORMS OVER CENTRAL TX
MAY EXPAND GRADUALLY NEWD THROUGH THE DAY AS HEATING ON THE ERN SIDE
OF MORNING COMPLEX RESULTS IN STRONGER INSTABILITY. SETUP IS
FAVORABLE FOR DAMAGING WINDS AND AN ISOLATED TORNADO OR
TWO...REFERENCE WW 286.
...NRN MI INCLUDING THE UPPER PENINSULA...
SURFACE HEATING AND COLD MID LVL TEMPERATURES WILL SUPPORT
THUNDERSTORMS SPREADING EWD ACROSS THE MI U.P. AND NRN LOWER MI.
COUPLED WITH 35-40 KT DEEP WNWLY SHEAR...A BAND OR TWO OF LOW-TOPPED
STORMS WITH MARGINALLY SEVERE HAIL AND WIND GUSTS ARE
POSSIBLE...REFERENCE MD 866.
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