SWODY3
SPC AC 070729
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT THU APR 07 2011
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN PORTIONS OF THE
CENTRAL PLAINS TO THE UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE LOWER OH
VALLEY SEWD TO ERN GA...SC AND WRN/SRN NC...
...ERN PORTION OF CENTRAL PLAINS TO UPPER MS VALLEY...
00Z GFS/ECMWF ARE IN BETTER AGREEMENT AS COMPARED TO THE LAST FEW
DAYS SHOWING THE WRN TROUGH BECOMING PROGRESSIVE ON SATURDAY AND
REACHING THE SRN/CENTRAL ROCKIES TO NRN HIGH PLAINS BY 12Z SUNDAY.
A BAND OF STRONG SWLY MID-UPPER LEVEL FLOW IS EXPECTED TO EXTEND
FROM THE SWRN STATES THROUGH THE CENTRAL PLAINS TO THE MID MO RIVER
VALLEY BY SATURDAY AFTERNOON. IN THE LOW LEVELS...LEE CYCLOGENESIS
IS EXPECTED ACROSS ERN CO THROUGH THIS FORECAST PERIOD...WHILE A
SECONDARY SURFACE LOW FORMING OVER NEB /LIKELY ATTENDANT TO A LEAD
IMPULSE/ MOVES INTO SRN MN BY 12Z SUNDAY. STRENGTHENING SLY LOW
LEVEL WINDS ACROSS THE SRN/CENTRAL PLAINS WILL ADVECT MOISTURE
NWD...WHILE A WARM FRONT MOVES FROM THE LOWER MO VALLEY TO THE UPPER
MS VALLEY. THE GREATEST MOISTURE RETURN WILL RESIDE E OF A DRY LINE
EXTENDING FROM THE NEB LOW SWD THROUGH CENTRAL OK TO CENTRAL TX.
A PLUME OF STEEP MIDLEVEL LAPSE RATES EXTENDING NEWD ATOP THE
MOISTURE RETURN WILL SUPPORT MODERATE TO STRONG INSTABILITY...WITH
GENERAL AGREEMENT IN THE MODELS SHOWING CONVECTIVE DEVELOPMENT FROM
MID-LATE AFTERNOON ALONG THE DRY LINE IN NRN OK TO THE MID MO
VALLEY. STRONG EFFECTIVE BULK SHEAR OF 50-70 KT WILL SUPPORT
ORGANIZED SEVERE STORMS. ACTIVITY IS EXPECTED TO DEVELOP/SPREAD
NEWD TOWARD THE UPPER MS VALLEY SATURDAY NIGHT AS THE LLJ VEERS AND
STRENGTHENS TO 60 KT WITH A CONTINUED LIKELIHOOD FOR STRONG TO
SEVERE STORMS.
...LOWER OH VALLEY SEWD TO ERN GA/CAROLINAS...
GUIDANCE SUGGESTS THE WEAK IMPULSE MOVING ACROSS THE SRN PLAINS ON
FRIDAY SHOULD TRACK SEWD FROM THE MID MS VALLEY WITHIN 40-50 KT NWLY
FLOW ALOFT REACHING THE CAROLINAS BY EARLY EVENING AND THEN MOVING
OFFSHORE. A WEAK SURFACE BOUNDARY EXTENDING FROM MO ESEWD INTO KY
AND OUTFLOW BOUNDARIES LEFT OVER FROM DAY 2 CONVECTION ACROSS PARTS
OF THIS REGION WILL BE THE FOCI FOR NEW TSTMS ON SATURDAY. LOW
LEVEL MOISTURE RETURN ON DAY 2 /FRI/ INTO THESE REGIONS WILL
CONTINUE ON DAY 3 /SAT/ WITH SURFACE DEWPOINTS INTO THE 60S ACROSS
THIS SLIGHT RISK AREA. THIS COMBINED WITH DIABATIC HEATING AND
7-7.5 C/KM MIDLEVEL LAPSE RATES SHOULD RESULT IN MODERATE
INSTABILITY /UP TO 1500-2000 J PER KG/. EFFECTIVE BULK SHEAR AROUND
50 KT WILL SUPPORT ORGANIZED STRONG TO SEVERE STORMS. GIVEN THE
DEGREE OF AVAILABLE INSTABILITY AND SHEAR... HIGHER PROBABILITIES
MAY BE NEEDED IN LATER OUTLOOKS...BUT UNCERTAINTY IN PRIMARY FOCUS
AREAS PRECLUDES THIS INCLUSION AT THIS TIME.
..PETERS.. 04/07/2011
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