SPC AC 281957
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT THU JUN 28 2007
VALID 282000Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE OH
VALLEY...CNTRL APPALACHIAN MTNS...MID-ATLANTIC AND SRN NEW
ENGLAND...
...NERN U.S....
A BROAD UPPER-LEVEL TROUGH OVER SERN CANADA AND THE NERN U.S. WILL
REMAIN IN PLACE THIS AFTERNOON. AT THE SFC...A COLD FRONT IS LOCATED
FROM SE NY EXTENDING WSWWD ACROSS PA INTO OH. SOUTHEAST OF THE
BOUNDARY...OBJECTIVE ANALYSIS SHOWS MODERATE INSTABILITY IN PLACE.
SFC HEATING AND LOW-LEVEL CONVERGENCE IS AIDING THE DEVELOPMENT OF
STRONG TO SEVERE CONVECTION ALONG THE BOUNDARY AND THIS LINEAR MCS
SHOULD CONTINUE TO ORGANIZE MOVING SEWD ACROSS THE MID-ATLANTIC
REGION THIS AFTERNOON.
RUC ANALYSIS SHOWS A BROAD MID-LEVEL JET LOCATED NEAR THE
CANADIAN-U.S. BORDER WITH 35 TO 45 KT OF MID-LEVEL FLOW PRESENT
ACROSS SRN NY...SRN NEW ENGLAND...PA AND NJ. THIS AREA OF THE SLIGHT
RISK SHOULD HAVE THE GREATEST POTENTIAL FOR SUPERCELLS CONSIDERING
THE ENHANCED VERTICAL SHEAR. SUPERCELLS SHOULD BE CAPABLE OF
PRODUCING WIND DAMAGE AND LARGE HAIL. FURTHER SOUTHWEST...VERTICAL
SHEAR IS NOT AS STRONG BUT OBJECTIVE ANALYSIS SHOWS MODERATE
INSTABILITY FROM SRN IND AND SRN OH ESEWD INTO VA AND NC. THIS
SHOULD BE SUFFICIENT FOR SCATTERED SEVERE STORMS CAPABLE OF
PRODUCING WIND DAMAGE. A SLIGHTLY GREATER POTENTIAL FOR WIND DAMAGE
MAY EXIST ACROSS VA AND NRN NC WHERE LOW-LEVEL LAPSE RATES ARE
LOCALLY VERY STEEP. THE SEVERE POTENTIAL SHOULD BE CLOSELY TIED TO
PEAK HEATING WITH THE SEVERE THREAT DROPPING OFF BY EARLY EVENING
ACROSS THE REGION.
...NRN AND CNTRL HIGH PLAINS...
AN UPPER-LEVEL TROUGH OFF THE COAST OF WA/ORE WILL APPROACH THE
PACIFIC NORTHWEST THIS AFTERNOON. SOUTHWEST FLOW WILL GRADUALLY
BECOME MORE ESTABLISHED OVER THE NRN ROCKIES AS A HIGH PLAINS
UPPER-LEVEL RIDGE DRIFTS SLOWLY EWD. SFC HEATING AND TOPOGRAPHIC
FORCING SHOULD ALLOW ISOLATED THUNDERSTORMS TO DEVELOP FROM WRN MT
EXTENDING SEWD INTO ERN WY. SCATTERED TO NUMEROUS THUNDERSTORM
COVERAGE SHOULD EXIST ACROSS ECNTRL CO.
THE LATEST OBJECTIVE ANALYSIS SHOWS MODERATE INSTABILITY EXISTING
FROM NE CO NWD ACROSS ERN WY WHERE MLCAPE VALUES RANGE FROM 1500 TO
2500 J/KG. ALTHOUGH VERTICAL SHEAR PROFILES ARE NOT THAT STRONG
ALONG THE INSTABILITY AXIS DUE TO THE UPPER-LEVEL RIDGE...ENOUGH
INSTABILITY SHOULD BE IN PLACE FOR ISOLATED SEVERE STORMS.
FURTHER NORTHWEST IN WRN AND CNTRL MT...MODERATE VERTICAL SHEAR IS
IN PLACE DUE TO AN APPROACHING MID-LEVEL JET ASSOCIATED WITH THE
UPPER-LEVEL TROUGH. THE SHEAR WILL BE FAVORABLE FOR ISOLATED
SUPERCELLS ESPECIALLY AS DESTABILIZATION CONTINUES LATE THIS
AFTERNOON. HOWEVER...THE SEVERE THREAT SHOULD REMAIN VERY ISOLATED
DUE TO THE WARM MID-LEVEL TEMPS IN PLACE ACROSS THE REGION.
..BROYLES.. 06/28/2007
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