SWODY1
SPC AC 261221
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0721 AM CDT THU APR 26 2007
VALID 261300Z - 271200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM THE NCENTRAL GULF COAST
NWD ACROSS THE OH VALLEY MIDWEST AND EWD ACROSS THE SRN APPALACHIANS
TO THE CAROLINAS...
..SYNOPSIS...
LOW CENTER BOTH SURFACE AND ALOFT LOWER MO VALLEY WILL LIFT NEWD
INTO LWR MI AREA BY END OF FORECAST PERIOD. WARM FRONT FROM MO LOW
EXTENDS EWD ACROSS CENTRAL IL/IND AND THEN ESEWD ACROSS WV TO ERN
VA/NC BORDER. WARM FRONT WILL LIFT NWD AHEAD OF LOW TODAY POSSIBLY
TO THE SRN MI BORDER. DRY SLOT ROTATING NEWD AROUND LOW WILL SPREAD
NEWD ACROSS TN/OH VALLEY TODAY AS STRONGER MID/UPPER WINDS SHIFT
E/NE ACROSS OH/TN VALLEY TO MID ATLANTIC STATES.
WARM SECTOR IN ADVANCE OF RATHER ILL DEFINED COLD FRONT S OF LOW TO
LA IS MOIST AND CURRENTLY ONLY MARGINALLY UNSTABLE.
..OH/ERN TN VALLEY...
THE DRY SLOT SPREADING ACROSS REGION THIS MORNING WILL ALLOW SURFACE
HEATING AND CORRESPONDING DESTABILIZATION OF THE MOIST WARM SECTOR.
WHILE SURFACE CONVERGENCE ILL DEFINED...EXCEPT POSSIBLY VICINITY
WARM FRONT MOVING NWD...BY EARLY/MID AFTERNOON INHIBITION WILL
WEAKEN SUFFICIENTLY FOR SURFACE CONVECTIVE INITIATION. ALTHOUGH
INSTABILITY EXPECTED TO GENERALLY REMAIN LESS THAN 1000 J/KG...7C/KM
LAPSE RATES...COOL MID LEVEL TEMPERATURES AND 40-50KT OF DEEP LAYER
SHEAR WILL SUPPORT LARGE HAIL POTENTIAL. WITH MODEL POINT
SOUNDINGS INDICATING 20-30KT OF LOW LEVEL SHEAR/HELICITIES FROM
100-200 M2/S2...PARTICULARLY VICINITY WARM FRONTAL BOUNDARY SUGGEST
LOW TOPPED SUPERCELLS ARE LIKELY. THIS WOULD BE ASSOCIATED BOTH
WITH LARGER HAIL AND A TORNADO THREAT.
..SERN STATES...
THE LINER MCS FROM NRN AL TO SERN MS PERSISTS AND WITH DAYTIME
HEATING EXPECTED TO INTENSIFY BY LATER THIS MORNING/EARLY AFTERNOON.
ALTHOUGH MODEST MID LEVEL LAPSE RATES WILL LIMIT THE CAPE TO
GENERALLY AROUND 1000 J/KG...40-50KT OF DEEP LAYER SHEAR COUPLED
WITH STEEP LOW LEVEL LAPSE RATES WILL LEAD TO INCREASED SEVERE
POTENTIAL. PRIMARY THREAT WILL BE DAMAGING WINDS.
..MID ATLANTIC STATES...
WITH STRONG HEATING TODAY IN CAROLINAS S OF WARM FRONT...AFTERNOON
CAPES WILL CLIMB TO 1000 J/KG WHICH COUPLED WITH A DEEPLY MIXED
BOUNDARY SUPPORTS A FEW STRONG/SEVERE THUNDERSTORMS. WITH MID
LEVEL LAPSE RATES ONLY AROUND 6C/KM AND 50-60KT OF DEEP LAYER
SHEAR...PRIMARY SEVERE CONCERN WOULD LIKELY BE DAMAGING DOWNBURST
WINDS GIVEN THE STEEP LOW LEVEL LAPSE RATES AND SFC T/TD SPREADS.
.HALES/GUYER.. 04/26/2007
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