SWODY1
SPC AC 120334
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
1034 PM CDT WED APR 11 2007
VALID 120320Z - 121200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE SERN
STATES...
..THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE OH
VALLEY...
AMENDED TO EXPAND THE SLIGHT RISK FARTHER NWD INTO SC AND NC
..NERN GA THROUGH CNTRL AND ERN CAROLINAS...
STORMS HAVE RECENTLY INCREASED IN COVERAGE AND INTENSITY PRIMARILY
WITHIN ZONE OF ISENTROPIC ASCENT N OF WARM FRONT ACROSS NERN GA.
THIS ACTIVITY IS EXPECTED TO CONTINUE NEWD THROUGH SC NEXT FEW
HOURS. MOST STORMS SHOULD REMAIN ELEVATED ABOVE A SHALLOW BOUNDARY
LAYER AND THIS SHOULD LIMIT PRIMARY THREAT TO HAIL. HOWEVER...THE
LOW LEVEL JET IS SHIFTING EWD THROUGH THIS AREA AND WILL MAINTAIN AN
INFLUX OF LOWER 60S DEWPOINTS AND AT LEAST MARGINAL INSTABILITY INTO
PORTIONS OF THE CAROLINAS. THE LOW LEVEL THETA-E ADVECTION SUGGESTS
STORMS COULD BECOME CLOSE ENOUGH TO SURFACE BASED TO POSE A
CONDITIONAL THREAT OF ISOLATED DAMAGING WIND AND POSSIBLY A TORNADO
OR TWO GIVEN FAVORABLE LOW LEVEL HODOGRAPHS.
..SERN STATES...
THIS EVENING A WARM FRONT EXTENDS FROM OFF THE NC COAST SWWD THROUGH
ERN SC THEN WWD THROUGH S CNTRL GA INTO CNTRL AL WHERE IT INTERSECTS
A COLD FRONT. THE COLD FRONT EXTENDS FROM SERN LA NEWD THROUGH SERN
MS INTO CNTRL AL THEN CONTINUES NWD AS AN OCCLUDED FRONT THROUGH
MIDDLE TN...CNTRL KY AND NWWD TO A SURFACE LOW IN E CNTRL IND.
WARM SECTOR FROM SRN AL THROUGH S CNTRL AND SRN GA REMAINS
MARGINALLY TO MODERATELY UNSTABLE WITH MLCAPE FROM 500 TO 1000 J/KG.
STRONGEST STORMS INCLUDING DISCRETE SUPERCELLS CONTINUE FROM NEAR
INTERSECTION OF THE WARM FRONT AND COLD FRONT OVER E CNTRL AL ESEWD
NEAR AND JUST S OF WARM FRONT THROUGH S CNTRL GA. ACTIVITY IS
DEVELOPING WITHIN ZONE OF FAVORABLE LARGE SCALE ASCENT JUST AHEAD OF
EWD ADVANCING DIVERGENT JET EXIT REGION. LOW LEVEL HODOGRAPHS AND
DEEP LAYER SHEAR WILL REMAIN FAVORABLE FOR SUPERCELL STRUCTURES
ACROSS CNTRL THROUGH S CNTRL GA NEXT FEW HOURS WITH A CORRESPONDING
THREAT OF LARGE HAIL...ISOLATED TORNADOES AND DAMAGING WIND.
OCCLUDED CYCLONE WILL REMAIN OVER THE OH VALLEY AND GREAT LAKES
REGION TONIGHT. HOWEVER...MODELS SUGGEST SECONDARY CYCLOGENESIS WILL
OCCUR LATER TONIGHT ACROSS VA AS THE DIVERGENT UPPER JET ADVANCES
TOWARD THIS REGION. AS THIS OCCURS...SRN BRANCH OF THE LOW LEVEL JET
WILL SHIFT EWD TOWARD THE ATLANTIC SEABOARD. THE STRENGTHENING LOW
LEVEL JET SHOULD RESULT IN NWD ADVANCEMENT OF WARM FRONT AND NWD
RETURN OF RICHER LOW LEVEL MOISTURE INTO CNTRL SC AND ERN NC. THIS
MAY CONTRIBUTE TO AT LEAST MARGINAL INSTABILITY WITHIN AN
INCREASINGLY FAVORABLE KINEMATIC ENVIRONMENT. FEEL AT LEAST A
CONDITIONAL SLIGHT RISK IS WARRANTED AS FAR N AS SRN SC WITH SOME
PROBABILITIES INTO COASTAL NC. HOWEVER...POTENTIAL LIMITING FACTORS
WILL BE LIMITED INSTABILITY AND TENDENCY FOR THE STRONGER FORCING TO
SHIFT N OF WARM SECTOR.
..OH VALLEY...
STORMS CONTINUE DEVELOPING WITHIN ZONE OF FAVORABLE ASCENT AND DPVA
IN ADVANCE OF OCCLUDED BOUNDARY WHERE SURFACE HEATING EARLIER TODAY
AND COLD AIR ALOFT CONTRIBUTED TO STEEP LAPSE RATES AND MARGINAL
INSTABILITY. STORMS HAVE EVOLVED INTO A DOMINANT LINEAR MODE FROM
SRN OH SWD THROUGH N CNTRL KY. DAMAGING WIND WILL REMAIN THE PRIMARY
THREAT WITH THIS ACTIVITY NEXT FEW HOURS AS IT ADVANCES EAST.
ACTIVITY WILL LIKELY WEAKEN BY LATE EVENING AS IT ENCOUNTERS AN
INCREASINGLY MARGINAL THERMODYNAMIC ENVIRONMENT.
.DIAL.. 04/12/2007
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