SPC AC 081731
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT MON SEP 08 2008
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID ATLANTIC INTO THE
NERN STATES...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE SRN FL PENINSULA...
...SYNOPSIS...
LOW AMPLITUDE PROGRESSIVE FLOW PATTERN WILL REMAIN OVER THE CONUS
THROUGH TUESDAY. UPPER TROUGH NOW MOVING THROUGH THE NRN PLAINS WILL
EJECT ENEWD THROUGH THE NERN STATES DURING THE DAY. WEAK SURFACE
CYCLONE IS FORECAST OVER THE LOWER GREAT LAKES IN ASSOCIATION WITH
FORCING FOR ASCENT ATTENDING THE SHORTWAVE TROUGH. BY EARLY TUESDAY
A COLD FRONT SHOULD EXTEND FROM THE SURFACE LOW SWWD THROUGH THE OH
VALLEY...THE WRN TN VALLEY AND INTO CNTRL TX. WARM FRONT WILL LIKELY
EXTEND SEWD FROM THE LOW THROUGH ERN PA. THIS BOUNDARY WILL LIFT NWD
INTO SRN NEW ENGLAND BEFORE THE COLD FRONT ADVANCES EAST AND OFF THE
NERN U.S. COAST EARLY TUESDAY EVENING.
...NERN STATES THROUGH MID ATLANTIC...
INCREASING SWLY BOUNDARY LAYER FLOW AHEAD OF UPPER TROUGH SHOULD
CONTRIBUTE TO ADVECTION OF 60S DEWPOINTS THROUGH MUCH OF THE NERN
U.S. PRE-FRONTAL WARM SECTOR. BY MID-DAY DEWPOINTS WILL LIKELY RANGE
FROM NEAR 60 OVER NEW ENGLAND TO THE UPPER 60S OVER THE MID ATLANTIC
REGION. HOWEVER...INCREASING LARGE SCALE ASCENT EARLY IN THE PERIOD
AHEAD OF THE UPPER TROUGH WILL LIKELY RESULT IN WIDESPREAD CLOUDS IN
MUCH OF NERN U.S. PRE-FRONTAL WARM SECTOR. MODEST MID-LEVEL LAPSE
RATES AND POTENTIAL FOR WIDESPREAD CLOUDS WILL LIKELY LIMIT MLCAPE
TO GENERALLY BELOW 1000 J/KG. MODERATE INSTABILITY MAY DEVELOP OVER
THE MID ATLANTIC WHERE STRONGER DIABATIC HEATING MAY OCCUR.
THUNDERSTORMS MAY BE ONGOING AT THE START OF PERIOD WITHIN ZONE OF
LIFT IN FRONTAL ZONE AND AHEAD OF THE FRONT FROM THE APPALACHIANS
INTO THE UPPER OH VALLEY. ACTIVITY WILL LIKELY INCREASE ALONG AND
AHEAD OF THE FRONT DURING THE DAY. A STRONG KINEMATIC ENVIRONMENT
WILL DEVELOP OVER THE NERN STATES IN ASSOCIATION WITH THE UPPER
TROUGH WITH NEWD TRANSLATING COUPLED LOW LEVEL AND MID LEVEL JET
STRUCTURES. WEAKER DEEP LAYER FLOW AND SHEAR PROFILES WILL EXIST
WITH SWD EXTENT INTO THE MID ATLANTIC WHERE GREATER INSTABILITY IS
EXPECTED. IF SUFFICIENT INSTABILITY DEVELOPS...THE KINEMATIC
ENVIRONMENT WILL SUPPORT ORGANIZED STORMS INCLUDING BOWING SEGMENTS
AS WELL AS SOME SUPERCELL STRUCTURES OVER THE NERN STATES. BOUNDARY
LAYER OVER MUCH OF NEW ENGLAND WILL INITIALLY BE STABLE NORTH OF
WARM FRONT WHERE LARGE LOW LEVEL HODOGRAPHS WILL EXIST...SO SEVERE
THREAT WITH NWD EXTENT INTO THIS REGION WILL LIKELY DEPEND ON HOW
FAR NORTH THE WARM FRONT RETREATS DURING THE DAY.
...LOWER MS VALLEY THROUGH TN VALLEY AND THE CAROLINAS...
OTHER STORMS WILL LIKELY DEVELOP IN VICINITY OF AND SOUTH OF THE
FRONT FROM THE CAROLINAS SWWD THROUGH THE SERN STATES AND LOWER MS
VALLEY WHERE MODERATE INSTABILITY IS EXPECTED WITH MLCAPE AROUND
1500 J/KG AND MODEST LAPSE RATES. THIS REGION WILL REMAIN SOUTH OF
THE STRONGER FLOW ALOFT WITH 10-25 KT AT 500 MB AND WEAK VERTICAL
SHEAR SUPPORTIVE OF MULTICELLS. A FEW STORMS COULD BECOME CAPABLE OF
PRODUCING ISOLATED STRONG WIND GUSTS AS BOUNDARY LAYER LAPSE RATES
STEEPEN...BUT OVERALL THREAT APPEARS LIMITED.
...S FL...
HURRICANE IKE IS FORECAST BY THE NHC TO CONTINUE NWWD ACROSS WRN
CUBA DURING THE DAY. SOME OF THE OUTER CONVECTIVE BANDS WILL LIKELY
STILL AFFECT PARTS OF SRN FL. BASED ON THIS TRACK LOW LEVEL
HODOGRAPHS ARE NOT EXPECTED TO BECOME PARTICULARLY LARGE...BUT MAY
REMAIN SUFFICIENT FOR A THREAT OF ISOLATED TORNADOES MAINLY ALONG
THE SWRN PORTION OF THE PENINSULA INTO THE KEYS.
..DIAL.. 09/08/2008
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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