SWODY2
SPC AC 051730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT SUN AUG 05 2007
VALID 061200Z - 071200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...CNTRL PLAINS AND UPPER MIDWEST...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NEW
ENGLAND...ERN NY...ERN PA AND THE MID-ATLANTIC...
..NRN AND CNTRL PLAINS/UPPER MIDWEST...
AN UPPER-LEVEL TROUGH OVER THE PACIFIC NORTHWEST IS FORECAST TO MOVE
SLOWLY EWD THROUGH MONDAY AS A SHORTWAVE TROUGH DRIFTS ENEWD INTO
THE NRN PLAINS MONDAY AFTERNOON. LARGE-SCALE ASCENT ASSOCIATED WITH
THE TROUGH AND MODERATE INSTABILITY SHOULD SUPPORT THE DEVELOPMENT
OF SCATTERED TO POSSIBLY NUMEROUS THUNDERSTORMS ACROSS THE REGION.
THE FAVORED LOCATION OF STORM DEVELOPMENT SHOULD EXIST NEAR A SFC
LOW IN SD AND ALONG A COLD FRONT EXTENDING SWD FROM SCNTRL ND ACROSS
SD INTO CNTRL NEB. MCS DEVELOPMENT MAY OCCUR MONDAY EVENING WITH THE
STORMS MOVING INTO THE UPPER MS VALLEY DURING THE OVERNIGHT PERIOD.
CONCERNING THE SEVERE POTENTIAL...MODEL FORECASTS MOVE A
WELL-DEFINED 60 KT MID-LEVEL JET FROM THE NRN HIGH PLAINS ACROSS ND
LATE TONIGHT INTO MONDAY. THIS FEATURE COMBINED WITH SLY FLOW AND
SUBSTANTIAL VEERING WITH HEIGHT SHOULD RESULT IN MODERATE VERTICAL
SHEAR ACROSS MOST OF THE REGION. THE VERTICAL SHEAR APPEARS
SUFFICIENT FOR SUPERCELLS ESPECIALLY WHERE INSTABILITY BECOMES
MAXIMIZED IN THE LATE AFTERNOON. SUPERCELLS THAT DEVELOP WILL LIKELY
BE CAPABLE OF PRODUCING LARGE HAIL AND WIND DAMAGE. AN ISOLATED
TORNADO THREAT MAY ALSO EXIST WITH STORMS LOCATED CLOSE TO THE
LOW-LEVEL JET DURING THE LATE AFTERNOON AND EARLY EVENING.
THE MAGNITUDE OF THE SEVERE THREAT SHOULD DEPEND ON HOW MANY STORMS
INITIATE. THE GFS PRESENTS THE LEAST AGGRESSIVE SCENARIO PRODUCING
VERY LITTLE CONVECTIVE DEVELOPMENT ACROSS THE DAKOTAS WHICH MAY BE
DUE TO THE TIMING OF THE APPROACHING WAVE AND WARM MID-LEVEL TEMPS
WHICH INTRODUCES UNCERTAINTY. HOWEVER...IF A SCENARIO CLOSER TO THE
NAM AND NAMKF VERIFIES...THEN AN MCS OR TWO SHOULD ORGANIZE IN THE
EVENING MOVING ESEWD ACROSS ERN SD INTO SRN MN AND NRN IA. THIS
WOULD BE MORE FAVORABLE FOR AN ENHANCED WIND DAMAGE THREAT ALONG
THIS CORRIDOR.
..MID ATLANTIC/ERN PA/ERN NY/SRN NEW ENGLAND...
AN UPPER-LEVEL TROUGH OVER ERN ONTARIO TONIGHT IS FORECAST TO MOVE
QUICKLY EWD INTO QUEBEC THROUGH MONDAY. THE SRN EXTENT OF THE TROUGH
SHOULD BE LOCATED ACROSS NEW ENGLAND BY MONDAY AFTERNOON. AT THE
SFC...A COLD FRONT WILL APPROACH THE REGION FROM THE NORTHWEST.
AHEAD OF THE COLD FRONT...MODERATE INSTABILITY SHOULD DEVELOP AND
SCATTERED THUNDERSTORMS WILL LIKELY INITIATE ALONG A PRE-FRONTAL
TROUGH. THE STORMS SHOULD MOVE EWD ACROSS SE NY...ERN PA AND SRN NEW
ENGLAND DURING THE AFTERNOON.
CONCERNING THE SEVERE POTENTIAL...FORECAST SOUNDINGS ACROSS THE
REGION SHOW VEERING LOW-LEVEL WINDS AND ABOUT 50 KT AT 500 MB. THIS
WILL CREATE MODERATE TO STRONG VERTICAL SHEAR ACROSS MOST OF THE
REGION MONDAY SUGGESTING ISOLATED SUPERCELLS AND ORGANIZED MULTICELL
CLUSTERS WILL BE POSSIBLE. A THREAT FOR LARGE HAIL AND WIND DAMAGE
SHOULD EXIST WITH THE STRONGER CELLS. THE LARGE HAIL THREAT WILL
LIKELY BE HIGHEST NEAR INSTABILITY MAXIMA WITH THE WIND DAMAGE
POTENTIAL GREATEST WHERE LOW-LEVEL LAPSE RATES ARE LOCALLY VERY
STEEP.
..NRN AND ERN MT...
AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL MOVE SLOWLY
EWD TONIGHT AS A SHORTWAVE TROUGH MOVES INTO THE REGION FROM THE
WEST ON MONDAY. LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-TROUGH
SHOULD PROMOTE ISOLATED THUNDERSTORM DEVELOPMENT ALONG AN AXIS OF
INSTABILITY LOCATED IN ECNTRL MT BY MONDAY AFTERNOON. COLD TEMPS
ALOFT AND MODERATE VERTICAL SHEAR SHOWN ON FORECAST SOUNDINGS
SUGGEST A MARGINAL HAIL THREAT MAY EXIST WITH THE STRONGER CELLS
LATE MONDAY AFTERNOON.
.BROYLES.. 08/05/2007
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