SWODY1
SPC AC 061240
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CDT SAT SEP 06 2008
VALID 061300Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN NORTH CAROLINA NEWD
INTO FAR SRN NEW ENGLAND...
...SYNOPSIS...
TC HANNA...LOCATED EAST OF RDU AT 12Z..IS FORECAST BY NHC TO
ACCELERATE NNEWD THROUGH THE PERIOD ALONG THE ERN SEABOARD...AS IT
BECOMES PICKED UP BY STRONGER SLY WINDS ALOFT. ELSEWHERE...A LARGE
SCALE TROUGH ALOFT WILL REMAIN SITUATED FROM THE NRN/CENTRAL ROCKIES
EWD INTO GREAT LAKES/OH VALLEY.
...NC NEWD INTO FAR SRN NEW ENGLAND...
TO THIS POINT...CELLULAR STORMS/TORNADOES HAVE BEEN VERY ISOLATED
WITH TC HANNA. HOWEVER...STORMS HAVE BEEN GRADUALLY INCREASING
WITHIN AN OUTER BAND LOCATED IN FAR ERN NC. SRH VALUES FROM
300-700 M2/S2 IN THE LOWEST 1 KM...COMBINED WITH MID 70 DEWPOINTS
AND SBCAPE VALUES NEAR 500 J/KG...WILL REMAIN FAVORABLE FOR AN
ISOLATED TORNADO/WATERSPOUT...ESPECIALLY FROM FAR ERN NC NEWD INTO
SERN MD THIS MORNING.
...CENTRAL/SRN PLAINS...
AROUND SUNRISE...A WEAK FRONT EXTENDED FROM THE SRN TX PANHANDLE EWD
INTO SRN OK. SWLY LOW LEVEL JET AT 25-30 KT HAD RESULTED IN
SUFFICIENT LIFT FOR ELEVATED CONVECTION ACROSS NRN OK/SRN KS
OVERNIGHT. THESE STORMS ARE EXPECTED TO DIMINISH LATER THIS MORNING
AS THEY SHIFT EWD INTO A MORE STABLE ENVIRONMENT AND THE LOW LEVEL
JET WEAKENS.
THE MORNING CLOUDS AND RAIN COOLED AIR OVER NRN OK ARE LIKELY TO
RESULT IN A HEATING DIFFERENTIAL BOUNDARY TO BECOME ESTABLISHED THIS
AFTERNOON FROM THE NRN TX PANHANDLE EWD INTO CENTRAL OK.
TEMPERATURES WARMING INTO THE 80S AND LOWER 60 DEWPOINTS WILL RESULT
IN MODERATE INSTABILITY. IF SURFACE BASED STORMS DEVELOP... DEEP
LAYER AT 40 KT WOULD SUPPORT SUPERCELLS AND A SEVERE HAIL THREAT
DURING THE LATE AFTERNOON/EARLY EVENING HOURS. HOWEVER... WARM LAYER
AROUND 850 MB ON THE OUN 12Z SOUNDINGS AND LACK OF DYNAMICAL FORCING
IS EXPECTED TO LIMIT CONVECTIVE DEVELOPMENT TO NO MORE THAN A STORM
OR TWO...SO ONLY LOW SEVERE PROB/S ARE FORECAST ATTM.
TONIGHT...ONCE AGAIN 25-30 KT LOW LEVEL JET SHOULD PROVIDE
SUFFICIENT WARM ADVECTION/FORCING FOR ELEVATED TSTMS TO DEVELOP
ACROSS SOUTH CENTRAL KS AND EXTREME NRN OK. SINCE LAPSE RATES ARE
EXPECTED TO BE STEEP BETWEEN 500 AND 700 MB ALONG WITH EFFECTIVE
SHEAR NEAR 40 KT...THE STRONGER STORMS MAY PRODUCE MARGINALLY SEVERE
HAIL. WEAK INSTABILITY SHOULD LIMIT A MORE WIDESPREAD SEVERE THREAT.
..IMY/GRAMS.. 09/06/2008
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