SPC AC 271634
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1134 AM CDT SUN JUL 27 2008
VALID 271630Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR THE
MID ATLANTIC INTO NEW ENGLAND...

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
TONIGHT FROM THE LOWER-MID MO VALLEY INTO THE NRN HIGH PLAINS...

...MID ATLANTIC TO NEW ENGLAND THIS AFTERNOON/EVENING...
THUNDERSTORM DEVELOPMENT IS UNDERWAY FROM NRN VA INTO SE NY ALONG A
SURFACE COLD FRONT AND IN ADVANCE OF A LEAD MID LEVEL SHORTWAVE
TROUGH. STRONG SURFACE HEATING FROM CENTRAL NJ SWD INTO VA/NC WILL
CONTRIBUTE TO ADDITIONAL DESTABILIZATION THIS AFTERNOON IN ADVANCE
OF THE FRONTAL STORMS...AND ADDITIONAL STORM DEVELOPMENT IS EXPECTED
ALONG A DIFFUSE LEE TROUGH. THE COMBINATION OF MLCAPE VALUES OF
1500-2500 J/KG...STEEP LOW-MID LEVEL LAPSE RATES...AND MODEST
EFFECTIVE BULK SHEAR /ROUGHLY 30 KT/ ALL APPEAR SUPPORTIVE OF STORMS
WILL DAMAGING DOWNBURSTS AND LARGE HAIL .
INSTABILITY WILL BE SOMEWHAT WEAKER FARTHER TO THE N ACROSS NY AND
NEW ENGLAND...AS A RESULT OF MORE WIDESPREAD CLOUDS AND LESSER
BOUNDARY LAYER DEWPOINTS. STILL...INSTABILITY SHOULD BE SUFFICIENT
FOR STORMS WITH AT LEAST MARGINALLY SEVERE HAIL AND A FEW DAMAGING
GUSTS THIS AFTERNOON.

...MIDDLE MO VALLEY TO THE NRN HIGH PLAINS THROUGH TONIGHT...
THE REMNANTS OF AN OVERNIGHT MCS CONTINUE TO MOVE SEWD INTO NW IA.
THIS CONVECTION IS ASSOCIATED WITH AN MCV WHICH IS EXPECTED TO
PERSIST THROUGH THE AFTERNOON/EVENING. THE SEVERE STORM THREAT HAS
DIMINISHED TEMPORARILY WITH THESE STORMS AS A RESULT OF SUBSTANTIAL
BOUNDARY LAYER CONVECTIVE INHIBITION. HOWEVER...DAYTIME
HEATING/MIXING WILL CONTRIBUTE TO DESTABILIZATION AND A GRADUAL
REDUCTION IN CONVECTIVE INHIBITION DURING THE AFTERNOON ALONG THE MO
VALLEY FROM NE/IA INTO NRN MO. GENERATION OF NEW STRONG/SEVERE
STORMS SHOULD OCCUR ALONG THE REMNANT OUTFLOW BOUNDARY BY EARLY-MID
AFTERNOON IN W/NW IA...WITH A SEWD EXPANSION OF THE ACTIVITY THROUGH
LATE AFTERNOON. THE COMBINATION OF MLCAPE VALUES OF 2000-3000 J/KG
AND EFFECTIVE BULK SHEAR IN EXCESS OF 40 KT /WITH THE MCV AND A
NARROW BELT OF ENHANCED MID LEVEL FLOW/ SHOULD SUPPORT BOTH EMBEDDED
SUPERCELL AND BOWING STRUCTURES CAPABLE OF PRODUCING LARGE HAIL AND
DAMAGING WINDS. BOUNDARY LAYER DEWPOINTS IN THE LOWER 70S AND
ENHANCED LOW-LEVEL SHEAR NEAR THE OUTFLOW BOUNDARY MAY ALSO BE
SUFFICIENT FOR A TORNADO OR TWO WITH INITIAL DISCRETE STORMS.
OTHER MORE ISOLATED SEVERE STORMS MAY OCCUR THROUGH THE PERIOD FROM
NE MT INTO THE DAKOTAS IN ASSOCIATION WITH EMBEDDED SPEED MAXIMA
ALOFT CRESTING THE MID LEVEL RIDGE.
..THOMPSON/BOTHWELL.. 07/27/2008